Maternal Industry: Cocoons of Orbweavers.
From: American Spiders and their Spinningwork
Henry C. McCook
The maternal industry of spiders is concerned chiefly in the preparation of the silken sac within which the eggs are deposited. It includes also the various methods by which this sac, when woven, is disposed of in order to secure a greater protection for its contents from exigencies of climate and weather, and assaults of enemies. I shall treat this part of my subject after the methods previously adopted, and describe in detail the cocooning habits of Orbweavers, and then present brief studies of the cocoonery of typical species of other tribes, with a view to comparison as to various points, such as the form, number, modes of preservation, and construction.
Among Orbweavers, the largest cocoon known to me is that of Basket Argiope. It is usually a pyriform or globular flask or sac of stiff, parchment like, yellowish silk, suspended in various sites by a series of short lines passing from all parts thereof to surrounding objects. These lines, at the points of attachment to the cocoon, diverge into minute conical or pyramidal deltas, similar to those formed to anchor the usual dragline when the spider walks.
The objects upon which the cocoons are hung depend, of course, upon the local habitat of the individual. For the most part, Argiope spins her web in low positions; on the tall grasses growing in the angles of a rail or “worm” fence; on the miscellaneous shrubbery that will be seen along the edge of a New England stone fence; in the low bushes of various sorts found in fields, lanes, the skirts of woods, and out of the way placesone will be sure to meet these pear shaped objects in October or early November.
A collection that lies before me as I write will be sufficiently typical of the positions in which Argiope spins her cocoons. Here is a cluster of tall grasses, upon which two cocoons are hung. One, with a brown external case, is suspended within a series of closely intersecting yellowish threads, which are lashed to the stalks of the grass eight inches from the roots. Just within the little concavity formed by the stems as they have been pulled together in a circular position, the little flask, with its precious contents, is swung. At the top of this clump a second cocoon is placed. It is of a yellowish white color, and, in order to give it a proper site, the tops of the spears of grass have been pulled down and twisted together, so that the capsules, or graceful clusters of seed vessels, hang around the cocoon on every side, giving it a beautiful setting. These cocoons are eleven inches apart, and were probably spun by two spiders.
Another example is bung in the very midst of a tall field chrysanthemum. The cocoon is much larger than those just described, and is of a rounder shape. Two branches of the plant have been drawn towards each other, and these again towards the central stalk. Within the space thus circumscribed the egg sac is suspended in the midst of a maze of lines attached at one end to the cocoon, and at the other to various parts of leaves and stems of the plant. It is about eighteen inches from the ground, and forms a pretty object amidst the balled white blossoms of chrysanthemum. (Fig. 39.)
A third and fourth specimens are hung in similar positions within the out-branching limbs of a wild flower unknown to me, which is thick set with little white blossoms. Still another is hung within a little canopy formed by the leaves of a blackberry vine, that have the beautiful hues with which, in our climate, the autumn is wont to paint the foliage. Still another is suspended beneath a similar canopy, formed of leaves on a young maple bush. Another has a similar site within the clustered leaves of a fragrant honeysuckle vine; and yet one more has been suspended upon the leaf stalks and under the leaves of our well known Virginia creeper. A pretty environment, indeed, this, last one, but of less stability than beauty; for, as the autumn advanced, and the leaves of the ampelopsis dropped to the ground, the egg case, so carefully wrought by the mother while expending upon it the last energies of her life, fell to the ground, and probably would have soon mingled with mother earth had it not been rescued by the collector’s hand. These cases will sufficiently illustrate the natural sites chosen by this spider upon which to suspend her cocoon.
The hanging of the silken flask is not without an evidence of nice care and discrimination in the adjustment of its supports. The guy lines are commonly so placed upon the different parts of the cocoon, and so stretched and fastened to adjacent objects, that the mother leaves her precious casket so well poised and finely hung that even the strongest wind fails to disturb its balance when a good position has been selected. In this position it will commonly remain until the brood is hatched; but, as we have already seen, sometimes the mother’s care is misplaced. It sometimes happens that the cocoon is simply anchored to leaves, and, when the autumn brings the usual fall of foliage, it is carried down to the ground. There, buried among rubbish, covered with snows and rains, the chances for development of the young are seemingly not very good. Yet even thus it is possible that, in sites comparatively undisturbed by tramping feet of men and animals, the eggs may remain healthful throughout winter, and yield their broodling Argiopes when spring suns dissolve the snow and the spring wind has scattered the leaves.
It is not an unusual thing for Cophinaria to hang her cocoon in the angle of walls in a house or outbuilding. (Fig. 40.) I have met a number of such cases in the outlying parts of Philadelphia, as, for example, Germantown and West Philadelphia. There still remain in those sections a number of gardens and spacious yards, within which this large and beautiful creature has maintained her position against all encroachments of civilization since the landing of the Swedish pioneers. Their snares are woven upon the vines which cluster about arbors, outbuildings, and verandahs and it is a common thing for the mother, when the cocooning time has come, to slip underneath a roof or cornice, and there suspend her egg sac.
In this case she protects it by a slender encasement of retitelarian lines spun entirely around it. A cocoon thus disposed is represented at Fig. 40, as it was found in the early summer in the basement of a hotel at Atlantic City. The enclosing lines were from seven to eight inches high, and of about equal width. The lines were much soiled by dust, the accumulation of winter and spring, but the cocoon proved to contain many healthy spiders, although in the lower part it was infested with parasitic ichneumon flies.
Another case of suspension within doors offered an interesting exception to the usual mode. This cocoon was hung in the angle of the walls of a room in Sedgley House, at Fairmount Park, Philadelphia, the headquarters of Captain Chasteau, of the Park Guard, who said that it was made about October 1st. When first observed, it was a round ball, which was gradually wrought into a pear shaped object. This, when I saw it, was hung from the under side of a sheeted curtain (Fig. 41), that curved over and extended like a bridge from the shield shaped hub of the snare to the adjacent wall. The curtain terminated in a pocket, from the bottom of which the cocoon was suspended. The cocoon was thus just behind the orb which was spun across the angle about seven feet from the floor. The characteristic zig-zag ribbon of the web extended well downward, and a number of lines stretched from side to side across the angle, nearly to the floor, forming a convenient gangway for the spider.
Immediately after finishing her work the mother spider began to languish. She would not take flies as aforetime when offered to her. Once she tried to escape from the room into the Park, but was brought back, and placed upon her lower gangway lines, which she mounted, with great apparent difficulty, to the central shield, behind which she stationed herself. She was found dead upon the floor one morning, having lived only a few days after the completion of her cocoon.
The cocoons of Cophinaria vary in length from five-eighths of an inch to one inch and five-eighths. Three measurements between these limits are one and a half, one and a fourth, and one and one-eighth inches. The bowl is generally about one inch wide, and the flask one-eighth inch wide at the tip of the neck. The bowls are for the most part decidedly pyriform in shape, but sometimes are spherical instead of oval. As the spiderlings grow a little within the sac after hatching, the bowl somewhat expands, or rather fulls out, but the original shape remains substantially unchanged.
The structure of the cocoon is as follows: First, the outer case or shell (Figs. 43, 44, o.c) is usually a thin, stiff, parchment like substance, that feels dry, and crackles under the touch, as though glazed. It is substantially water tight. I have found several cocoons of a softer material, and thicker, much like a delicate yellow felt. The glazing above mentioned is not the result of ageing or weathering simply, but is produced by the action of the spider herself, perhaps by the overspreading of the viscid secretion which forms the beads on the spirals of a snare.
When this outer case is cut away there is first presented a flossy envelope (f.e) of soft yellowish silk, which quite surrounds the contents of the bowl. Next is a dark brown pyriform or spherical pad of spinningwork (p.d), which swathes the eggs completely, interposing a thick, warm, silken blanket between them and the external case. On the upper part of this pad is a plate or cup (c.u), of like color and closer texture, with the concavity downward. I have at least once found this to be a whitish disk of stiff silk. The neck or stalk (nk) of the cocoon is filled with a compact silken cone (c.s), of a yellowish or brown color, which is united at the base to the egg plate (c.u), and at the top terminates in a strong twisted cord (c.s), which sometimes extends upwards and forms the central support to the cocoon. Next to the brown pad is often a thin flossy envelope, which surrounds the egg sac. The latter is a rather closely spun pouch of variable tenacity, and whitish or pinkish white color, that encloses the thousand or more eggs which lie in a globular mass within the heart of the cocoon. The inner egg sac (e) is attached above to the plate or cup (c.u), which, after the spiderlings hatch, is pushed upward by them not unlike a trapdoor, permitting them to creep out into the surrounding padding, leaving their white shells within the sac.
The plate serves to support the eggs, which are probably oviposited upward against it. One female, confined within a box got so far in the construction of her cocoon as to spin the plate, but went no farther, leaving, however, this evidence of the point at which her ovipositing would have begun.
The genus Argiope is widely distributed throughout the globe, and the cocooning habit of the species has elsewhere the same characteristics as in America. Argiope fasciata of Southern Europe and Northern Africa makes a cocoon much like that of our Cophinaria. Fig. 46 shows the external case, and Fig, 45 gives a section view of the central egg sac, supported in the midst of a bunch of loose flossy silk.1
I have found numbers of Cophinaria’s cocoons on vacant city lots in Philadelphia, strung to the stems of tall weeds on either side of a well traveled footpath. The mothers had safely passed through the perils of assaulting boys and voracious birds, and left these tokens of their maternal care in this conspicuous spot. As far as examined the cocoons contained broods of healthy spiders. One exception, however, permitted me to see the position and structure of the egg mass. It is a hemispherical mass five-sixteenths of an inch high and wide. The eggs are bright yellow, contained within a delicate white or pink lined membranous silken sac, through which they can be seen in outline.
It is interesting to observe that there is some variety among the mother Argiopes in the manner of preparing a cocoon. I have one before me which is composed, first, of a soft silken exterior case; then, of three easily separated layers of delicate yellow silken tissue, extremely soft and beautiful. Next to these layers is the loose yellow flossy mass hitherto described, and then the brown padding which surrounds the egg sac proper. This brown padding is not as abundant as I commonly find it, for the reason, perhaps, that the yellow silken envelope is so much more pronounced. Another cocoon before me has in it nothing but the brown padding, scarcely a trace of yellow floss, and no layers such as above described. I account for the distinct layers by supposing that they were woven between well marked intervals of resting.
The Banded Argiope is not as common a spider, at least in the immediate vicinity of Philadelphia, as her congener Cophinaria. Her life appears to be prolonged a little further into the autumn, for I find her upon the bushes when the Basket Argiope has entirely disappeared. Her cocoon is therefore made, as a rule, somewhat later; but it is suspended in a similar manner and in similar sites. I do not find it often, and, as compared with the cocoon of Cophinaria, it is rare. It seems to be less fond of human society, or else less able to stand the exigencies of civilization than Cophinaria. In outlying sections, where Nature has been less disturbed by men, it may probably be found more readily.
It is suspended by means of silken guys to the leaves and stalks of grass or low growing plants, which are bent over and also lashed together above the swinging egg nest in the manner represented at Fig. 47. Again, it may be found as at Fig. 48, swung in the midst of a retitelarian maze woven amidst the branches and leaves of a bush, or, as at Fig. 49, seated and suspended in the crotches of a wild meadow flower.
The shape of her cocoon differs from Cophinaria’s in being hemispheroidal instead of pyriform; in other words, it resembles the lower half of a spheroid. Across the wide top is stretched a circular piece of silk, like the head of an Indian drum. (Fig. 50.) The outer case is of stiff yellow silk, as is also the head or top; this part, in a cocoon now before me, is somewhat darker in color than the rest of the case. A marginal flap surrounds the head, and has various points to which guy lines were attached in site. (See Fig. 50.) The height and width of the cocoon are about the sameone-half inch. When the outer case is cut aside, as at Fig. 51, the interior is seen to consist, first, of a yellow flossy envelope, which is packed between the inner wall; and, second, an egg pad, which is not composed of purple silk as in Cophinaria, but of yellow silk plush loosely woven, and is three-eighths of an inch long. Within this are the eggs. Immediately above is the egg cover of white silk plush, which is commonly flat, not concave as with Cophinaria. It is about one-eighth inch thick, and is attached firmly by silken threads to the inside of the top of the case. Against this cover, no doubt, the eggs are oviposited upwards, and are then covered by the mother spider. The portion of the egg cover is shown at Fig. 51, where one edge adheres to the remaining part of the top of the case, and also at Fig. 52, where the object is viewed from the side.
Among various other examples of California spinningwork received from Mrs. Eigenmann and Mr. R. L. Orcutt, of San Diego, were several cocoons of rare beauty. They were lenticular or hemispheroidal masses, of a yellowish, yellowish green, and green color. (See figures, Plate IV.) They were pulled out into angles at the flat side, as though they had been suspended by threads at the angular points. They varied somewhat in size, from three-fourths of an inch to an inch long, one-half inch wide, and three-eighths high. It was long a matter of wonder and discussion with me what species formed these beautiful egg nests. Mr. Orcutt finally attributed them to Argiope argenteola, without giving a reason for his opinion. The question was at last settled by a living female specimen of that spider sent me by Mrs. Eigenmann, which, happily, reached me alive, but very feeble. I placed her under a trying box, fed her with water and flies, and she revived. The following morning a cocoon was hung within the box, whose shape and color solved the mystery, and proved that Mr. Orcutt was correct in attributing the cocoon to Argenteola.
This cocoon was a keystone shaped patch of white sheeted silk, upon which was raised a greenish button that enclosed the egg mass. (Fig. 53.) The white color of the sheet can hardly be characteristic, for in specimens before me this part is green.
The whole was suspended between lines that were attached above to the lower foundation lines of the orb, and to the sides and bottom of the box beneath. Evidently the spider, in spinning her cocoon, had first stretched the sheet, and against or within this had placed her eggs, which she then proceeded to overspin in the usual manner, though, of course, it is not impossible that in this and like cases the cocoon may be framed upon a flat surface and then raised and suspended in the above described position. In general appearance this cocoon resembles that of Epeira rather than the typical Argiope cocoons as represented by our two familiar species, Cophinaria and Argyraspis. But in the manner of suspension, as well as the character of the egg case, Argenteola resembles her congeners.2
A cocoon, when dissected, shows two principal partsthe basal sheet above referred to, and the cup or case which is set upon it. Both these parts consist of closely woven silk, like that which forms the outer case of Cophinaria and Argyraspis, the latter of which it most resembles. This cup is of a yellow or yellowish green color, and the deep green tints appear most decidedly in slight flossy tufts, which here and there overspread it. The surface of the basal sheet is overspread with white silk. Within the case is a ball of white flossy curled silk, which forms the inner upholstery of the nest. It thus appears, that while the cocoonery of this remarkable spider resembles that of Epeira in its external shape and the nature of the interior furnishing, yet in the texture of the case and manner of suspension it is like the cocoonery of its congeners. In the example produced in my trying box the basal sheet is hung vertically. If it were suspended horizontally, with the egg case downward (Fig. 54), it would closely resemble an Argyraspis’ cocoon.
Mrs. Eigenmann tells me that Argenteola makes more than one cocoon. A specimen which had spun a web in her sitting room placed a cocoon upon it somewhat in the position observed by myself, as above described; but shortly after (the time is not specified) a second cocoon was formed upon the web about two inches below the first one. A few days previous to this cocooning the spider neglected to eat, and paid no attention to the flies placed upon her web. The discoverer had concluded that the creature’s mission was ended and death would soon ensue, but was surprised to find its lethargy only the condition naturally preceding cocooning. The second cocoon was a little larger and more flocculent than the first.
After this maternal duty the mother disposed of the flies that were entangled in her web, without any hesitation. This was not the end of the matter, however, for on the 14th of December, just three weeks after the second cocoon had been spun, a third was made, which was likewise attached to the web. On the afternoon of January 6th, three weeks after this last maternal act, the spider lost her grip upon the meshes of her web and fell dead to the floor, having been in the possession of the observer three months.
The genus Epeira, which includes our best known and most numerous species of Orbweavers, has little variety among its most typical species in the form of its cocoons, the manner of protection, and nature of sites selected for them. The general form is that of a ball, hemisphere, or semiovoid mass of thick, silken floss, that enswathes a white silken bag, within which a number of eggs, usually yellow, are massed. This is fastened in any convenient and eligible position, attached directly to the surface or hung amid supporting threads. I have stripped from a decaying trunk a bit of bark eighteen inches long, on which one, could count forty or fifty of these cocoons intermingled with those of Agalena nævia and other Tubeweavers, and of Laterigrades, is well as the white silken tubes of Saltigrades. (Fig. 55.) Often the dried bodies of the mothers, who had died shortly after their last maternal care and work, were found clinging to the nurseries of their young. When deposited in such sites the eggs rarely have any other protection in the way of spinningwork than the flossy cocoon case, the shelter of the bark being, no doubt, sufficient barrier against assault of enemies and stress of weather. A favorite site of this sort is the trunk of an old hickory tree, whose flaky outer bark, curled up at the free ends, offers an accessible retreat.
A cocoon of Insularis, in my collection, spun within a small paper box, is a globular ball of yellow silken plush three-fourths of an inch in diameter and of a light yellow color. (See Plate IV., Vol. II.) It is hung against the side of the box (Fig. 56) in the midst of a maze of short right lines an inch and a half wide and high. These lines are knotted together at innumerable points, which are marked by little white dots. This meshed envelope extends nearly to the cocoon, and certainly appears to be a sufficient barricade against hymenopterous invaders, although it was not able to save the eggs from those universal and well nigh irresistible pests of collections, the Dermestidae. I have another cocoon of this species similarly disposed within an inverted glass tumbler, under which the mother had been confined. She attached herself to the bottom of the glass (the top when inverted), and, as is the custom of her kind, hung there back downward until the period of cocooning. (Fig. 57.) Not long after she died, and her dried up form is partly shown in the drawing. The spots upon the glass represent the points of attachment for the supporting lines of the cocoon, and are little pats of adhering silk.
Sometimes cocoons are found laid against a leaf which has been drawn around it, as at Figs. 58 and 59, reminding one of the manner in which certain lepidopterous larvae protect themselves before they pass into the pupa state. When this sort of protection is secured for the eggs, viz., a leafy covering around the egg pad, no further envelope is added, precisely as when the eggs are laid upon the under side of bark and stones.
In other cases, however, as in the angles of walls, porches, outhouses, etc., the silken egg pad is itself enclosed in a tent of spinningwork more or less open. (Fig. 60.) In some cases this tent is little more than a series of lines drawn across the angle at a little distance from the cocoon, as at Fig. 61. Strix, Sclopetaria, and Domiciliorum are all in the habit of weaving around their cocoons such a tent.
A Domicile spider, which I found in the act of completing her cocoon, was content with a scantier covering than this. Her egg sac was an oval mass of yellowish brown silk one and onefourth inch long by three-fourths of an inch wide. It was fastened upon a twig of pine tree. At one end short lines were thickly strung across from the needle like leaves, making a sort of “fly” or awning. This was repeated at the other end, thus about half covering the cocoon. The mother spider hung to a few threads above (Fig. 62) her egg nest, with shrunken abdomen, and so much exhausted is to be little incurred to move. This cocoon was made September 24th.
For the most part the outer tent is of closer texture than those above described, being in fact an enclosing curtain of silken cloth, through which the outline of the cocoon within may be traced. (Fig. 63.)
Great numbers of these tent enclosed cocoons may be seen at the boat houses near the inlet of Atlantic City and Cape May. They are made during the last days of May and to the middle or last of June, and again in the fall.3 The cocoons measure seven-eighths of an inch long by six-eighths of an inch wide, and less. The enclosing tent measures two and a half inches long by one and three-eighths inch wide. Frequently the tents are overlaid one upon another, or spun close to each other, as at Fig. 58. I have found three large cocoons thus overlaid, and the outer tent, four inches long, covered the others so completely that one might have supposed the whole to be the work of one spider. Undoubtedly, these works are precautions against both enemies and the weather, which, although without experience of the effects of either upon her offspring, the mother takes as though she really foresaw the danger.
If an egg nest of this class be opened there will be found, in order, first, the outer tent, separate from the covering of the cocoon; second, a thin white silken sheet, which is the outer envelope of the cocoon proper; third, the thick egg pad of curled silk, usually yellow; fourth, the eggs, a conical or hemispherical or spherical mass of small yellow globules. (Fig. 64.) When the spider oviposits against a flat surface, the eggs are generally laid upon a coating or sheet of silk spread upon the surface, and the padding is then woven over it in the manner of Argiope cophinaria. If the cocoon is suspended within a maze of lines, the eggs are laid in the midst of the curled nest or egg pad, which is afterwards completed.
The cocoon of Epeira cinerea shows a variation from the common type of her congeners. The egg pad is a large flattened hemisphere, an inch in diameter, and one-fourth to three-eighths of an inch thick. This is spun against some flat surface, the boards of a shed, as I have seen it, upon a light cushion of curled yellow silk. Over and around this, on all sides, is woven the egg pad, which is flattened down quite compactly, and the whole mass lashed at the edges to the surface. The entire cocoon has a diameter of one and five-eighths inch or more, and is a quarter or three-eighths of an inch thick at the centre. (Fig. 66.)
Epeira triaranea makes a cocoon of the common type, but smaller. Of two now before me, spun in bottles, one measures one-fifth of an inch, and the other about half that. They are both round or ovoid flossy masses, protected by a maze of intersecting lines spun around them. This maze is often thickened into a tent, in which condition I have observed numbers spun in the angles of the joists of a cellar at Atlantic City, in the early spring (May 22d), full of young spiderlings just ready to emerge. These cocoons measured one-half inch long, which is somewhat above the normal length.
One female was observed (New Lisbon, Ohio), whose cocoon was wrapped up within a rolled leaf. This was swung to a cord, attached at one end to the silken, bell shaped tent within which the spider nested, and at the other end to the fence top against which the tent was placed. (Fig. 67.) In this way the mother had her future progeny literally “cradled,” and in good position also to be freely “rocked.” What freak had caused her to make this divergence we can only conjecture; probably the cocoon had first been spun upon the leaf, which, becoming loose, and threatening to fall, was secured in the manner described.
A familiar resort of Triaranea in New England is the stone wall, characteristic of that section. Underneath the irregular slabs or boulders of granite which are heaped, one upon the other, to form the division fences between meadows, etc., I have found large numbers of this species. The orb, which is usually about six inches in diameter, is woven within the interspaces of the rocks, and the spider has her resting place against the rough surface, or within the little indentations of the stone which forms the top of the cavity. Against this surface the mother Triaranea weaves her bowl shaped tent, and against the same surface, an inch or two away, she spins her cocoon. This is about a quarter or three-eighths of an inch in diameter; is a hemispherical disk of flossy white silk, which is overspun by a stiff, taut, close, but transparent tent of white silk about three-fourths of an inch long. This may be considered the typical cocoon of the species.
The number of eggs in three cocoons counted was, respectively, forty-five, forty-two, and thirty-two. They were of a gray color. Little spiders had just developed in. one, and these had yellowish abdomens, round, and very slightly oval, with the legs white. The egg skin had just been cast, and the little fellows were stretching themselves and straggling about in a feeble manner.
One female was resting within a circular depression underneath a rock, and had spun a few silken lines, forming the foundations of a little circular tent, the framework of which extended downward toward her snare. Within this was an old empty cocoon, against which the spider rested. Near by was a fresh cocoon, nearly one-fourth inch in diameter, overspun by a tough silken tent, and this appeared to belong to the spider, who, moreover, looked as though she might soon make another cocoon. The question was started, but was not solved, does Triaranea weave more than one cocoon? The cocoon was a little flossy ball, flattened, of course, on the side attached to the rock. I captured one of the females, which cocooned in a box, thus showing that the cocoons above described were those of this species.
A cocoon of Epeira thaddeus was sent to me from Vineland, by Mrs. Mary Treat. It had been spun upon some potted ferns within her lodgings. It is a subglobose sac, of a delicate pearl gray color, one-fourth inch (six millimetres) in diameter. It is attached at the top to a strip of silk ribbon, or rather it widens out at the top into two triangular points, by which it is fastened upon a cord stretched between two sprigs of fern. The egg ball thus swings free. (Fig. 68.)
I have secured cocoons of this species, by confinement within the trying box, which differ from the above. They are globular or subglobular masses of flossy yellow silk, about three-eighths of an inch in diameter. I believe that, ordinarily, Thaddeus will be found to weave a cocoon of this sort upon a leaf or other surface, probably enclosing it within a curled leaf, or over-spinning it in the manner of Epeira triaranea.
I have not been fortunate enough to identify the cocoons of our common Zillas; but a species which I observed in Florida made a cocoon shown at Fig. 69, top of the cut. It was a flossy ball, about three-eighths of an inch thick, and was woven within the silken tent which formed the spider’s domicile. It was placed in the top of the tent, and against the twigs, which formed a sort of framework for it. After the cocoon had been made the spider shifted her domicile to a lower point, and gradually spun a new dome shaped tent just beneath her cocoon, within which she continued to dwell.
The cocoon of Nephila wilderi, according to Professor Burt Wilder,4 is a large flossy hemisphere of silk, which is usually spun upwards against a leaf or similar surface. The spinningwork is of a yellow color, and so slight as to show the loose mass of eggs within. (Fig. 70.) It appears to resemble quite exactly the cocoon of its congeners in Africa and the West India Islands. For example, the cocoon of Nephila nigra, according to Dr. Vinson,5 is of a beautiful yellow color, and is attached to the bark of trees, or spun against the surface of some recess. Nephila maurata spins a large cocoon, of a beautiful orange yellow color. This is not attached to her snare, but is woven against any adjacent recess, or in some shaded place near to her, although sometimes she goes quite a distance from her web to find a cocooning site. The orange colored egg sac is enclosed in a flossy envelope of a paler color.6
If we may credit the statement, or rather the illustration of Mr. Wood, the Nephilas of the West Indies, which are there known as the Tufted spider, spin a cocoon similar to that described, but suspended to the stalks of various plants, instead of being hung beneath leaves or woven against hard surfaces.7 The figure presented by Mr. Wood, and which is here reproduced, is said by the author to be made from specimens in the British Museum, although I do not remember to have seen these when examining the collections of spinningwork at Kensington several years ago.
I have several cocoons of our American Gasteracantha, two of which were sent from Southern California by Mrs. Eigenmann. A third was woven by a living female sent from the same section; and a fourth was received from Dr. George Marx, of Washington. The latter is attached to the bark of a twig, upon which it is spun. It is a flossy button or wad of a bright yellow color. The outer strands of the spinningwork have a glossy appearance. It is about three-fourths inch long and one-half inch wide. (Fig. 72, and Plate IV., Vol. II.) The California examples are smaller but similar.
These cocoons are, in structure, like those of their African congeners as described by M. Vinson.8 This author describes a cocoon of Gasteracantha bourbonica as an ovoid, round and flattened, woolly wad of a yellow and green color. The case which envelops it is twenty millimetres long, and the central egg mass measures four-fifths of an inch (ten millimetres) in width. The centre, which contains the eggs, is white, but grows brown from the moment of enclosure.
The cocoon of Meta menardi, as I have found it, is a somewhat oblong roll of brownish silk, not very compact in texture, but sufficiently open to allow one to see the eggs enclosed within. It is deposited near the snare of the female, and simply attached to some surface by a rather sparing system of supporting lines.9 According to Blackwall, the species (Epeira fusca) as observed by him in North Wales makes a cocoon somewhat different from this. In autumn the female fabricates a large oviform cocoon of white silk, of so delicate a texture that the eggs, connected together by silken lines in a globular mass a quarter of an inch in diameter, may be seen distinctly within it. Its transverse axis measures about eleven-tenths of an inch, and its conjugate axis eight-tenths. It is attached by numerous lines, generally forming a short pedicle on one extremity to the walls or roofs of the places it inhabits. (See Fig. 74.) The eggs, which are yellow and spherical, are between four and five hundred in number.10 The general characteristics of the cocoon as thus described by Blackwall correspond with those of the American species, except in the habit of suspending the cocoon by a short pedicle. However, a wider observation of the American species might show even closer resemblance in cocooning habit. One or two of my specimens have a little tuft at one pole, as though a slight stalk or attachment had been there made.
The cocoon of Tetragnatha extensa is a pretty object. I have never seen the mother weaving it, nor have I obtained it by confining the female within my trying boxes. But I have found it in the fields, where one may identify it by its resemblance to that spun by European individuals of the species; and, moreover, I have hatched the young, and thus demonstrated the true cocoon. It is an ovoid object, about quarter of an inch long and three-sixteenths of an inch wide and thick, and is commonly woven against a leaf, or twig, or bit of bark, or other convenient object. (Figs. 75, 76.) I have found what I suppose to be this cocoon, suspended by four diverging lines within an open space, as, for example, in the post hole of fences, as shown at Fig. 77. The cocoon varies somewhat in color, being usually of a cream white tinted with green. The silk looks almost like wool. The exterior is covered with little points or minute projecting rolls, in this respect somewhat approximating the cocoon of Uloborus. Within this exterior case are found the eggs, which are over-spun by a slight flossy covering.
The English species forms its cocoon in June. It is described as roundish, less than one-fourth inch in diameter, fine and slightly woven; and is either whitish with greenish tufts, or greenish with whitish tufts upon its surface. The cocoon is fixed to some object near the web, and contains pale yellow eggs.11 This corresponds substantially with the account of Walckenaer, who describes the threads of the interior as of a bluish green color, but the exterior as a little browner in hue, and presenting inequalities as of little globules produced by the eggs.12 Lister also describes the cocoon, which he frequently found attached to the joints of twigs and to the leaves of plants. Thus it was nearly or quite the first example of spider cocooning to attract the notice of naturalists.
Most Orbweavers habitually make but one cocoon. There are some exceptions, however, among them two species, very common in the United States, viz., the Labyrinth spider and the Tailed spider, which distribute their eggs in several cocoons, as does also Epeira bifurca of Florida. A rarer species having the same habit is the Basilica spider; Uloborus plumipes and Cyrtarachne complete the list of Orbweavers known to me to habitually construct a string or cluster, of egg sacs. These species represent groups having well defined differences in structure and decided differences in the characteristics of their snares.
The genus Cyrtarachne is remarkable by the peculiar form of the body, and is distributed quite extensively throughout the United States. There are probably two species, the Bisaccata of Emerton and Cornigera of Hentz. The cocoon made by the two species is similar in general form, but there appears to be a marked difference in the mode of attachment. Moreover, Cornigera apparently spins but one cocoon, while Bisaccata, as its name implies, spins at least two; and I have had cocoon strings sent me from California by Mrs. Eigenmann containing three. Thus Emerton’s specific name appears to be a misnomer. I have a number of specimens; one collected by Dr. Marx at Washington, D. C., a single cocoon; another containing two cocoons, sent to Dr. Marx from Fort Yukon, Alaska. Still others were forwarded to me from various parts of the country. The range of the species is, therefore, evidently from the southern extremity of California to the Alaskan peninsula on the west, and in the east along the New England coast, and as far south at least as Washington.
Several of my specimens are fastened to the twigs upon which they were woven, and give a correct idea of the ordinary manner of attachment. The cocoons are about three-eighths of an inch in length, with a foot stalk of varying length, which gradually ends in a fine thread stretched upward along the twig. One example, containing two cocoons, is lashed against a twig by an overlying cord of yellowish silk five inches long. The cocoons are composed of dark brown or bluish silk, with overspread tufts or patches of white. They are separated by a space of nearly half an inch, and the foot stalk of the lower cocoon is united to the bottom of the upper one by a thick, stiff, blackish cord.
The lower portion of the ball of the egg sac has a scalloped fringe with blunt points or processes, which, as far as my specimens show, have nothing to do with the manner of suspension. Nevertheless, they may serve some useful purpose in anchoring the egg sac to the twig. This description will fairly represent the form and mode of suspension of all my specimens.
Emerton found his specimens at New Haven, Connecticut, on a beech tree. They were dark brown, as dark as the bark of the tree, and as hard. Around the middle of each was a circle of irregular points. One of his cocoons was attached by a string to the bark, and the other was attached in the same way to the first cocoon. The spider held on to one of the cocoons, which, therefore, had probably been recently spun. We may safely conjecture the date of this observation, October 22d, to be the cocooning period of this species. The following spring another similar pair of cocoons was found on a low oak tree in the same vicinity, still firmly attached to the bark. From these the young came out in June.
In my specimens there is much difference as to the regularity of the little exterior processes or points alluded to. In some specimens they are quite regularly formed, and make a very pretty ornament upon the cocoon. In others they are quite irregular, not only in their shape, but in the mode of arrangement, being little more than irregular nodules upon the surface. One of the specimens from California consists of three cocoons, the first of which has the points arranged with considerable regularity, while the others are less in size and are almost without rugosities. All have little openings towards the top, through which, no doubt, the spiderlings made their escape. (See Fig. 80, which shows the cocoons natural size.)
Cyrtarachne cornigera is quite as remarkable in the character of its cocoon as in its own structure. This cocoon is a flask shaped object, resembling that of Argiope riparia, but with a neck relatively much longer. Two examples before me differ greatly in size, one being more than one-third larger than the other.13 In the former the stalk or neck is of uniform thickness; in the latter it is twice as thick at the mouth as at the bowl. (Fig. 81.) The cocoon is lashed at the base of the bowl to a twig by a number of silken threads, which are attached to one side, carried quite around the twig, and similarly fastened to the opposite side. The entire lower half of the bowl is thus covered by the attached wrappings, which are drawn so tightly that the flask sits quite firmly upon the twig. At the opposite end the cocoon is stayed by lines that pass from the tip of the stalk to the snare of the spider or other support. The attachments of these guys are shown in Fig. 81, which is drawn twice natural size.
In the Camden cocoon (Fig. 82, natural size), the lashings are of a yellow, glossy silk, and so abundant as to make quite a ribbon. Here the threads are carried around both sides of a projecting twig, as though the spider mother had purposely availed herself of this mechanical advantage, and are additionally strengthened by being crossed or twisted as they pass around the branch to which the cocoon is attached. The outer envelope is in color a very dark yellowish brown, and is of extraordinary stiffness. When cut open the bowl is found to contain a ball of white silken floss, within which the eggs are deposited. This ball is fastened to a very tough twisted cord, that passes up through the neck (Fig. 83), and which is the line by which the egg ball was suspended before the outer flask was spun around it. The texture of the external shell has every appearance, under the lens, of having been hardened by means of a viscid secretion applied to it by the spider; the toughness is evidently not the result of simple weaving.
Another example of Cornigera’s cocoon is drawn at Fig. 84. The manner in which the bowl of the vase shaped object is seated upon the twig and lashed by a ribbon is there well shown. The top of the stalk is stayed by various lines wrapped about a neighboring twig.
Epeira labyrinthea belongs to the small group of Orbweavers that spin compound snares; that is, snares in which the orb is associated with a well developed retitelarian snare.14 The labyrinth of crossed lines is placed behind and above the orb, and within this the spider has her dwelling, commonly beneath a dry leaf; here also she suspends her string of cocoons, placing them near her tent, and usually above it and to one side, as represented in Fig. 85.
It consists of several, usually five, lenticular or semiglobular vessels, of a yellowish, tough texture, about one-fourth inch long and one-sixth wide. These may be properly described as woven dishes with covers. Each cocoon consists of two disks joined together at the edges tightly enough to cause them to adhere until the parts are gradually loosened before the strain of the growing spiderlings, and finally open up and permit the inmates to escape.
These disks, on examination, present very uniformly the appearance shown at Fig. 88, a, b. The lower part of the cup, is an oval dish twice as long at the top as at the bottom, reminding one of the form of a portable bath tub much in vogue. The upper disk, the cover or cap, is in shape a miniature soft slouch hat with a rounded crown and turned up rim. The rim of the cap fits upon a minute corresponding lip of the cup. When the eggs are first laid the cocoon has a somewhat flattened appearance, which in many cases (not all) becomes much rounded as the spiders grow. If the cap be lifted up or pulled off, as may readily be done when the young are nearly ready to emerge, a ball of yellow silk will be found inside, amidst which the eggs are originally deposited, and in whose fibres the spiderlings burrow. The cocoons are in number about five, more or less, and each one contains about twelve to twenty eggs, so that the aggregate number of eggs is about equal to that found in the single cocoons of some other species.
For the most part the cocoons overlay one another, the top of each projecting one-third to one-half its length over its neighbor, as shown at Fig. 89, i, front view; ii, back view. They are held together chiefly by a band of loose threads (o, ii) which are stretched along the back parts of the cups, although at the points where the cocoons overlap they are also lightly attached. The band upon which the cocoons are thus strung is fastened to a strong, thick, branching white cord, which is anchored above and below to the network of cross lines. This cord is usually longest above, delt-ated and often suspended upon a similar transverse cord. (See Figs. 85, 86.) When the cocoons are opened in October, the spiderlings are found fully developed, lively, and ready to escape. They resemble the adult form in markings.
The cocoons are sometimes separated from each other, as at Fig. 86, but again are all overlaid, Fig. 87, being lashed together by the band of threads upon which they are strung. Occasionally, the spider will spin her tent beneath the lowest cocoon of the series, instead of the usual leaf or other debris, and will be found backed up against the same, holding to the trapline of her snare. (Fig. 90.) The full page cut (Fig. 85) shows Labyrinthea’s cocoons strung in natural site, above and behind the leaf-roofed tent.
The mother begins to spin her cocoons in August, adding one every week, or thereabouts, until the tale is complete. The suspensory cords that support the cocoon string are strong, thick, and of a pure white color. I have found numbers of the empty cocoon shells in the early spring, hanging intact upon the bushes where they had been placed, although, of course, the snare had entirely disappeared.
The Tailed spider, Cyclosa caudata, differs from Labyrinthea in the mode of hanging her string of egg sacs. This is suspended within the limits of her orb, above the central space, along the line of the perpendicular. As the cocoons increase in number, the adjacent radii and the connecting spirals are cut out, leaving a clear segment resembling that in the snare of Zilla, in the middle of which the cocoon string hangs. (Fig. 92.) The number of cocoons appears to vary much; I have usually found from three to five; Hentz never observed more than five.15 They are generally in shape a double cone, although often round or roundish, and are from three-sixteenths to quarter of an inch (five to seven millimetres) long and one-eighth inch (three millimetres) wide. A cocoon is not composed of two distinct parts, like one of Labyrinthea’s, but is spun in a single piece of soft yellowish floss, externally close enough to be weatherproof, but which ravels out into woolly threads when picked with a needle.
Within, the sac is filled abundantly with delicate, flossy, yellow silk, in which the eggs are deposited. These vary in number; for example, three now before me, opened in succession, contain, respectively, twenty-two, two, and ten; certainly a remarkable difference. On one occasion a female enclosed within a paper box began to make a cocoon, but proceeded no further than to weave a tiny saucer, similar to that spun by Argiope riparia. This would, therefore, appear to be the commencement of her cocoon, and it may be that against such a disk Caudata habitually deposits her eggs before enclosing them. However, I have not found this within her cocoons, as is the case with Argiope’s, and conclude that the disk is made the basis of the external sac, into which it is woven as the spider proceeds. The cocoons are often well separated upon the string, but also are found touching and even overlapping one another like tiles. Sometimes nodules of flossy silk, or of silk mixed with the debris of captured and devoured insects, are irregularly interposed between the cocoons. This is, indeed, a fixed and most interesting habit of the species, which will be described in a succeeding chapter.
During a temporary stay in Florida, April, 1886, I found nested upon the porch of Dr. Wittfeld’s place, Fairyland, Merrit’s Island, on the Indian River a little way below Rockledge, a new spider, which I named Cyrtophora bifurca. Its snare resembles that of Cyclosa caudata. It also resembles that spider in the manner of hanging its cocoon string in the vertical axis of its orb just above the hub. The character of the cocoon, however, differs entirely from that of Caudata. It is, in shape, a somewhat irregular octagon, and is of a dark green color. I have found as many as fourteen cocoons in one string, overlapping one another in the manner of cocoons of the Labyrinth spider, and which may also be seen at times with the cocoons of Caudata, although for the most part, the latter are arranged at intervals along the string. (See Figs. 96, 97.)
The cocoon strings collected varied in the number of cocoons attached thereto, probably according to the period of advancement in the process of ovipositing on the part of the mother. Of the specimens collected one string contained fourteen, another twelve, and another ten cocoons. They are bound together, along one side, by continuous series of thick white threads, which extend from the top to the bottom of the string. Each cocoon consists of two parts, which have evidently been fastened together by a selvage. These parts present the appearance of two dishes placed together edge to edge. They are woven of a soft, but rather tough, texture. A very slight tuft of flossy white silk is found inside, and within this the eggs are deposited. In one cocoon of a string of thirteen, twenty-five minute dead spiders were counted, which had passed their first moult. In another cocoon, taken from a string of five only, there were twenty-six. The number varies a good deal, however. The cocooning period appears to extend into May; at least I have received from Miss Anna Wittfeld, as late as the middle of June, a string, in which were some cocoons empty, one with spiderlings passed the first moult several days, and another with young who had just broken the egg. There was no trace of the bifurcated abdomen upon these younglings. The spider is of a uniform light green color, about the shade of its cocoon.
Another Orbweaver that makes several cocoons is Epeira basilica. I am indebted to Dr. George Marx, of Washington, for the specimens from which the following studies and drawings have been made, as well as for the information concerning Basilica’s habit of caring for her eggs. The number of cocoons is five, thus corresponding with that of Labyrinthea, and generally with Caudata. They are round, covered on the outside with gray spinningwork, and united by a cordage so stiff that the series stands out like a stick. They are attached to a triangular patch of yellowish white silk, which is an expansion of a long, glossy, strong linen like cord, composed of many threads, by which the string of egg balls is suspended. (Fig. 98.)
According to Dr. Marx, whose observations were made at Washington, the string is hung just above the centre of Basilica’s peculiar domed snare, and wholly or in part within the dome, as represented at Fig. 99. The mother has position beneath her egg bags, back downward, as is the habit of Orbweavers making horizontal snares.16
When the cocoon is dissected, it is found to consist, first, of an exterior sac of gray material; within this is next enclosed a round black case (Fig. 100), four or five millimetres in diameter, having a thin shell of remarkable hardness, in this respect resembling the cocoon of Cornigera. When illuminated and examined under the microscope this egg ball is seen to be composed of yellow silken fibre of exceeding fineness, and so closely woven that, looked at when within its bag, it is quite black. The paper like stiffness of the ball could hardly be caused by even such fine spinning, and I believe that the fibres are smeared with a viscid secretion, which gives them their peculiar stiffness. When this black case is cut open it is seen to contain flossy silk (Fig. 101), which forms the customary wrapping of the eggs and nest of the young spiders.
The cocoon of Uloborus is about one-fourth inch long, and one-eighth thick. It is drawn out at either pole into a point, and the surface is covered with small pointed or blunted processes. (Fig. 102.) It is made of a pure white silk, quite stiff of texture. Several of these cocoons (I have never found more than three) will be found united together so closely that they appear to be but one object, and, not strung loosely, by attaching threads, as is the case of some other spiders that make several cocoons. However, in this respect, the habit may differ. As a rule these cocoons are stretched like those of Cyclosa caudata, along the axis of the mother’s horizontal orb, and are thus immediately under the maternal care. (Fig. 103.) In this position I have seen them in New Jersey, and thus Mrs. Treat has observed them, and so also Mr. Emerton has described them. (Fig. 104.) Our American species appears in this respect to have the same habit as the European species, Uloborus walckenaerius.
This mode of disposing of the cocoon, however, cannot be universal, for I possess a specimen, received from Dr. George Marx, which is stretched along a little twig, to which its orb was attached, at a point slightly above the cocoon string. (Fig. 105.)
Hentz describes the cocoon of Uloborus mammeatus as tapering at both ends, in color whitish, with veins of brownish black, and with many small tubercles. He collected it in Alabama in dry places.18
The division here indicated between species habitually making a single cocoon and species habitually spinning several is, on the whole, a natural one; but there are certain facts to be noted which throw a measure of uncertainty around any such generalization. For example, it has long been supposed that Argiope cophinaria spins but one cocoon; and, judging from its size and the number of eggs that are found therein, one would seem to be sufficient to guarantee the continuance of the species. I have no doubt that, as a general rule, Cophinaria makes but one cocoon, but that there are exceptions is very certain.
Several years ago a clerical friend brought me two cocoons of this species, which had been spun on his premises by the same spider. Mrs. Mary Treat has discovered what appears to her to be a variety of Argiope cophinaria, which makes four cocoons, and which she accordingly named Argiope multiconcha.19 She sent me a string of these cocoons, of which there were four, of the general shape and about the usual size, strung within a few inches of each other. They had been spun against the wall of a kitchen in a house in. Western Missouri. The spider mother was also sent, but the specimen was much dried up, and in such a condition that it could not be very satisfactorily studied. It seemed to differ in no particular from Argiope cophinaria. If it be indeed the same species, what are the peculiar circumstances that have caused such a remarkable variation in habit? Is it true that Cophinaria does, more frequently than has been supposed, indulge in the luxury of an additional egg case? Two cocoons of this lot were opened and found to contain young spiders that had hatched, but died within the egg sac. The spiderlings were not counted, but they were very numerous.
During the summer of 1888 a female Cophinaria was discovered in the Farmers’ Market of Philadelphia upon the meat stall of one of the butchers. She had probably been brought into the market from the country, hidden among vegetable leaves, as the huge tarantula and the large Laterigrade spider, Heterapoda venatoria, are brought to our port from the West Indies in bunches of bananas and other fruit. Or, she may have floated in, as a young balloonist, from some city garden; for the species is abundant in open grounds within the city limits. Instead of brushing her down and killing her, after the usual manner of dealing with such creatures, the farmer took a fancy to preserve her, and would allow no one around his stall to inflict any injury upon her. She wove her characteristic web against one of the iron rods for suspending meat, chickens, game, etc., and there remained secure during the season.
Some time between the 10th and 20th of August she began to make a cocoon, which she enclosed within a little tent of interlacing lines, after the manner of that represented at Fig. 40. About a week or ten days thereafter she made a second cocoon, placing it in a position sixteen inches above the other. Both of these cocoons I saw precisely as they were left by the spider. They were spun within tents of crossed lines, five or six inches long and four or five wide, with a thickness of between two and three inches. The lines constituting the under edges of the tent were attached to the post of the stall on which the orb was spun. The upper tent had its roof lines sustained and drawn out from the post by the foundation lines of the orb. (Fig. 106.) The lines composing the tents were of a greenish yellow silk, similar to that used in the construction of the cocoon cases.
I removed the cocoons and opened them. The lower one was an inch and a quarter long and seven-eighths of an inch wide; was composed of a soft, yellow silken plush, and inside was constructed precisely like the ordinary egg sac of this species. It contained one hundred and twenty eggs, all of them sterile. The only peculiarity was that the stem which one usually finds at the top was missing. The second cocoon was not quite so large, one inch long and five-eighths of an inch wide, but was more perfect in shape, containing the usual stem. The eggs within this cocoon were also sterile, and the number did not exceed fifty. The number of eggs in both cases is small as compared with the usual fecundity of the species.
We may probably account for the making of the second cocoon by some abnormal condition of the ovaries, which prevented the ovipositing of all the eggs at once. The first lot, when extruded, were protected in the usual manner. Subsequently Nature compelled the mother to get rid of the remaining eggs; and, moved by the same impulse which covered the first lot, she was excited to overspin the second also.
This species will sometimes make a cocoon, or a part of one, in confinement, and I have observed that she will occasionally do the same in natural site. I have the branch of a bush which shows the beginning of a cocoon, being the little cup against which the eggs are spun, and also what appears to be the inner egg bag. There is nothing more, and the whole is stayed and shut in by the usual tent like spinningwork. Near by is a perfect cocoon, secured in quite the same manner. If we suppose that these two were made by the same spider, as is highly probable, we may infer that the original cocooning purpose of the mother was diverted in some manner, perhaps by alarm, which drove her from the spot. She returned to enclose the work partially done, but, moved by the urgency of motherhood, presently found a neighboring site, and finished her maternal duties.
Epeira diademata habitually spins but one cocoon; but the Spanish investigator, Termeyer,20 in the early part of this century, discovered and announced that she would spin as many as six cocoons when specially nourished. The fact strikes me as an extraordinary one, and I have never felt quite free to fully admit it.