OCCASIONAL PAPERS NATURAL HISTORY SEGIETY OF WISCONSIN. VOL. 1, NO. 3. MILWAUKEE: PRINTED FOR THE SOCIETY. 1890. Sabihadd ADDITIONAL OBSERVATIONS SEXUAL SELECTION SPIDERS OF THE FAMILY ATID, WITH SOME REMARKS ——— MR. WALLACE THEORY OF SEXUAL ORNAMENTATION, — Ty GEORGE W. AND ELIZABETH G. PECKHAM. (CRAMER, AIKENS & CRAMER, . .- ENGRAVERS AND PRINTERS, . ° - . . MILWAUKEE, WIS. ADDITIONAL OBSERVATIONS ON SEXUAL SELEC- TION IN SPIDERS OF THE FAMILY ATTID/. GEORGE W. AND ELIZABETH G. PECKHAM. In the species of Attidee whose mating habits we have heretofore described, the adornments displayed by the male in courtship have consisted of bright color on the cephalothorax or abdomen, colored hairs on the clypeus, tufts or ridges of hair over the face, modifications of the color or form of the first pair- of legs, or modifications of the falees. We have had for some time in our collection three species, all belonging to the same genus, whose males showed a peculiar enlargement of the third leg; thus in Habrocestum peregrinum the patella is enlarged and somewhat triangular in shape, with an apophysis, of vari- able length, projecting over the tibia, while the anterior face of the patella has a black spot on a white ground. The third leg of the male of Habrocestum ccecatum has a similar, but less striking, enlargement of the patella; and in an as yet un- described species, Habrocestum howardii, the patella has the same modification. The general appearance of this structure, together with the fact that it was limited to the males, and was very variable, sug- gested that it was one of those sexual adornments which are useful in gaining the favor of the female. Had it occurred on the first leg we should have felt reasonably sure that this was its function ; but it seemed improbable that a modification of the third leg could be displayed with advantage during court- ship, and we were therefore considerably in doubt as to its meaning. On the first day of June of the present year we were so fortunate as to discover on a hot, stony hillside (on ground, by the way, that we had worked industriously for ten years) large numbers of males and females of a new species of Habrocestum, having a modification of the third leg (Fig. 1) very similar to that 118 PECKHAM. [Vol. 1, of Habrocestum peregrinum, but carried to a much higher degree. As it was their mating season, we had now a welcome opportunity of seeing what use the active little male, which is further beautified by ay : : : : ge having his first legs of a delicate light green (a >» . . . . Y ! Le color, with a fringe of white hairs along 4.7 the outer side, makes of this adornment in paying his addresses to the female.* Z j The display was witnessed not only by Fig. 1—1hird leg of new ourselves, but by Mr. Wm. M. Wheeler, a eee who made several sketches on the spot. When they are put into a mating-box together, the male notices the female at a distance of from six to eight inches, and rapidly approaches her. When within three or four inches, Fig. 2.—New Habrocestum, showing position of first and third legs of male in courtship (from nature). the begins to move from side to side, with his handsome first legs pointed downward and somewhat outward, his palpi extended parallel with them, and his third legs raised above the first and second in such a way as to show the apophyses on the patelle. Frequently, in these preliminary movements, he bends the ends of the first legs inward—the bend being at the tibia—so as to put them into the form of a diamond, mean- while moving the palpi rapidly up and down. As he ap- *To show how a species may appear and disappear within a short time, we may mention that while on June Ist we found eleven males and six females in an hour, one week later four and a half hours’ hunting on the same spot gave us only one male aud no emales, : No. 3.] SEXUAL SELECTION IN SPIDERS. 119 proaches the female, she all the time eying him most intently, he raises the first pair of legs, swaying them backward and forward, still keeping the third pair well up, seeming as eager to display them as the first pair (Fig 2). In this way he approaches to within about two » inches, when she rushes at him and he retreats. The whole per- formanceisrepeated. Whenhe gets to within an inch of her, he lifts the first legs nearly at right eau: ae S ate Fig. 3.—New Habrocestum, showing angles: with the body, giving Moa Tis ob uals when approaching them a bowed position, with the tips approaching each other, so that each leg describes a semi- circle, while the palpi are held firmly together in front. Up to this time he has held the body well above the ground, but, now he lowers it by spreading out the second and fourth pairs, at the same time bringing the tips of the third pair nearer the body and arching the legs over the posterior part of the cephalothorax in such a way that the proximal ends of the tibice nearly meet (Fig. 3). As he stands in this position the female, who is watching him eagerly, has the front surface of the apophysis plainly in view over the dorsal surface of the cephalo- thorax, and his face and elypeus are also well exposed (Fig, 4). Now he approaches her very slowly, with a sort of creeping movement. When almost near enough to touch her he begins a very complicated movement with the first pair of legs. Directing them obliquely forward, he again and again rotates ae ee eon each leg around an imaginary point just ormamentation (frm beyond the tip; when they are at the lowest . point of the circle he suddenly snaps the tarsus and metatarsus upward, stiffening and raising the lee and thus exposing more completely its under surface. While this is going on with the first pair, he is continu- 120 PECKHAM. [Vol. 1, ally jerking the third pair up higher over his back, as though unable to get them into a satisfactory position, and the abdo- men is kept twitching. At one time he carried on these movements within one-sixth of an inch of the female for six - minutes, and at another time for five minutes; then she dashed at him and it all started over again. This display indicates that the enlargement of the third leg is useful in pleasing the female during courtship. In all probability the similar formations in peregrmum, ccecatum and howardit serve the same purpose. At the same time that we discovered the new Habrocestum, we found, for the first time in this neighborhood, some exam- ples of A. leopardus Hentz. The male of this species is very striking, from the fact that his clypeus is of a lovely turquoise blue—a most unusual color among spiders, where the blues are almost invariably metallic and iridescent. The male of leopar- dus is also adorned by having the space above the first row of eyes, extending to the second row, covered with brick-red hairs. Te matures, as is usual in spiders, before the female. His courtship is as follows: On seeing the female, which he does when eight or ten inches away, he approaches her slowly; when within three or four inches he begins to sway from side to side by bending all the legs on one side and extending the opposite ones, and then _ reversing the process, at the same time advancing. ‘The palpi are stretched out sideways, thus exposing the blue clypeus. As he moves, the female eyes him attentively and seems to be interested in his display. When quite near her he raises the first legs and holds them perpendicularly upward, and then, as he comes closer, lowers them so as to touch her. This seems to frighten her, and she runs off. The whole performance is repeated six or eight times before she finally yields, either to his boldness and persistence, as Mr. Wallace would have it, or to the combination of these qualities with grace and beauty. Sometime ago we published an account of the mating habits of Synageles picata, not, however, giving any figures. Tlaving captured some fresh males and females early in the No. 3.] SEXUAL SELECTION IN SPIDERS. 121 present season, we first repeated our experiments with them in order to verify our former results, and then sent them to the Figs. 5 and 514.—Synageles picata. Positions of male approaching female (from nature). well-known arachnologist, Mr. J. H. Emerton, who made from life the following sketches. To render them more intelligible, we repeat the account of the love-dance given in our former paper. * «These are ant-like spiders. The most important sexual difference is the greater thickness of the first legs of the male. These are flattened on the anterior surface and are of a brightly Fig. 6.—Synageles picata. Male as he appears from the side when approaching female (from nature). iridescent steel-blue color. Unlike most of the Aitid males this species keeps all his feet on the ground during his courtship: raising himself on the tips of the posterior six, he slightly inclines his head downward by bending his front legs, their convex surface being always turned forward. His abdomen is lifted vertically so that it isata right angle to the plane of the cephalothorax. In this position he sways from side to side (Figs. * Occasional Papers of the Wisconsin Nat. Hist. Soc., p. 43. 122 PECKHAM. [Vol 1, 5 and 53). Aftera moment he drops the abdomen, runsa few steps. nearer the female, and then tips his body and begins to sway again (Fig. 6). Now he runs in one direction, now in another, pausing every few moments to rock from side to side and to bend his brilliant legs so that she may look full at them. We were much impressed by the fact that the attitudes taken by the males served perfectly to show off their fine points to the female. We had never known the male of this species until the day that we caught this one and put him into the mating-box, and it was while studying his courtship that we noticed how he differed from the female in his iridescent first legs. He could not have chosen a better position than the one he took tomake’ a display. We had six females in-the box, and we saw him mate with all of them.” The rule for the male Altus, when dancing before the female, is either to raise or stretch out the first legs, the appar- ent object being to display the colored hairs and other append- ages with which they may be ornamented, as in the Icius mitratus, or to take an imposing attitude, as in Phileus militaris; or else to lower these legs so that they may not inter- fere with a view of the ornamented face or clypeus, as in Dendryphantes capitatus. In Synageles picata we are struck by the entirely unique position of the male, and, moreover, by the fact that this position is the only one which would serve to display his principal sexual adornment. If the legs were raised, outstretched, or held close to the ground, the effect of the flattened and iridescent anterior surface would be lost. This is a good example of what we have again and again observed in the courtship of the Attidee—that whatever fine points of color or structure the male possesses, his actions before the female display them to the very best advantage; indeed, he seems to have a strong consciousness of every advant- age, and to sedulously strive to bring it to the notice and impress its beauty upon the mind of the female to whom he is paying his addresses.* The females, on the other hand, are *We do not say that, in our opinion, he zs conscious of his strong points. It is quite conceivable that the tendency to perform the antics may have developed along with the beauties which they serve to display without any idea of their existence dawning in the mind of the spider. No. 3.] SHXUAL SELECTION IN SPIDERS. 123 as “ uncertain, coy, and hard to please” as the males are eager. Both Dr. McCook and Mr. Emerton have remarked that the female, in mating, seemed to do nothing but run away, and this often does seem to be her only idea at the beginning of the courtship. After a little, however, her attention is caught, and she lingers for a moment before turning away, and, as the affair progresses, she becomes excited and watches the male with absorbing interest, only turning to flee when he comes close to her. Tt may be well to say in this connection that any one who wishes to make a study of the mating habits of spiders should have a considerable knowledge of their haunts, their habits and of the time at which each species matures. The spiders should be taken just at the point of reaching maturity, as after that period their interest in the matter is only lukewarm, and although they may make some display it is but a feeble sug- gestion of their eager and excited action at an earlier time. Moreover, the observer must be prepared to draw largely upon his stock of patience, as some of the best dancers do not show what they can do just at first. For example, Habrocestum splendens will sometimes remain sulky and sullen for hours in the box with females, but when he is well warmed up to.an interest in them (this is not altogether figurative, as it is often necessary to put the box in the hot sunshine) he becomes per- fectly wild with excitement. In a former paper we set forth some facts and arguments in favor of Darwin’s theory of sexual selection, considering at the same time Mr. Wallace’s counter-theory by which he attempts to explain the superior beauty of the male in many species of birds and insects. Since then, in his extremely interesting and suggestive work on Darwinism, Mr. Wallace has summed up his former views on this subject, supplementing them with additional arguments. Having here brought forward some new facts in regard to the courtship of spiders, we take this opportunity of re-considering the theory that Mr. Wallace would substitute for the one offered by Darwin. THE THREE PARTS OF MR. WALLACE’S THEORY. It is of primary importance to see what evidence Mr. Wal- lace brings forward in support of the proposition which forms 124 PECKHAM. [Vol. 1, the whole foundation of his theory that the more brilliant and itense color of the male is due to his greater vigor and activity, and higher vitality. This proposition is a complex one, holding within it three implications which must be proved before its acceptance can be demanded—first, that male animals have higher vitality. than females; second, that those males that have the highest vitality have also the most brilliant and intense colors; and third, that the superior ornamentation of these males is due to their activity. FIRST PART: RELATIVE VITALITY OF MALES AND FEMALES. Mr. Wallace does not say, in so many words, that males have higher vitality than females; he assumes this to be so universally acknowledged as to need no proof. Thus he says: “The very frequent superiority of the male bird or insect in brightness or intensity of color, even when the general colora- tion isthe same in both sexes, now seems to me to be, primarily, due to the greater vigor and activity and the higher vitality of the male.” * And again: “The more vivid colors and more developed plumage of the males, I am now inclined to think, may be wholly due to their greater vital energy.”+ In view of the fact that a contrary opinion has been generally held (Darwin, in “Origin of Species,” says that the vitality of the two sexes is probably about equal), we object to the assumption of Mr. Wallace, and shall endeavor to show that in all probability the female, at least among birds and spiders, has as high vitality as the male. Before we can discuss this point we must ask, What are the criteria of high vitality ? Mr. Pocock, in a review of our former paper on this sub- ject, ubjects to our using activity and pugnacity as the only tests of vitality. As a matter of fact, these are the only ones put forward by Mr. Wallace; and, so far as the question is one of relative vitality among males, we are unable to suggest any that are better. When it comes to determining the relative vitality of males and females, we must also take into account the *Tropical Nature, p. 198. + Tbid., p. 213 No. 3.] SEXUAL SELECTION IN SPIDERS. 125. reproductive processes. Here the demand upon the female is obviously heavy. Even in birds and insects, where the embyro develops outside the body of the parent, the numerous eggs must be formed and stored with highly nutritious material, and there seems no room for doubt that in these relations the female evinces an amount of vital power that at least equals that ofthe male. How does she compare with him in pugnacity and activ- ity? Of birds we cannot speak with much authority, but it seems fair to say that in the construction of the nest, in feeding and rearing the young and in supplying her individual needs, the female shows as much activity as the male, while she ex- ceeds him in the anxious vigilance with which she watches over her young and the vigor with which she defends them from the enemies which constantly menace their safety. As to spiders, we have no hesitation in saying that the females are both more active and more pugnacious than the males. In “ Darwinism” Mr. Wallace supports his position by the following quotation—-not of facts, but of opinion—from the eminent arachnologist, Rev. O. P. Cambridge: “T myself doubt that particular application of the Darwin- jan theory which attributes mule peculiarities of form, structure, color and ornament to female appetency or predilection. ‘There is, 1t seems to me, undoubtedly something in the male organ- ism of a special and sexual nature which, of its own vital force, develops the remarkable male peculiarities so commonly seen, and of no imaginable use to that sex. Inas far as these peculi- arities show a great vital power, they point out to us the finest and strongest individuals of the sex, and show us which of them would most certainly appropriate to themselves the best and greatest number of females, and leave behind them the strong- est and greatest number of progeny. And here would come in, as it appears to me, the proper application of Darwin’s theory of natural selection, for the possessors of greatest vital power being those most frequently produced and reproduced, the ex- ternal signs of it would go on developing in an ever-increasing exaggeration, only to be checked where it became really detri- mental in some respect or other to the individual.” 126 PECKHAM. [Vol. 1, We oppose to this opinion of Mr. Cambridge, most of whose work has been done in systematic arachnology, that of the Rey. Henry McCook, who has devoted many years to a study of the habits of spiders, and who must be considered an important witness on a puint to which he has given especial attention. We ourselves had supposed that in the sedentary group the male spiders were more active and vigorous than the females until converted to the contrary opinion by his argument. He says: “Blackwall and Mr. C. Spense Bate reported to Darwin: that the males of spiders are very active and more erratic in their habits than those of females. This appears to be a gen- eral opinion among arachnologists, upon what ground as to the matter of activity I am not able to perceive. One, of course, is compelled to ask what is meant by activity and inactivity as applied to spiders. Certainly the words must be regarded as relative terms. ‘There is a sense in which the females of seden- tary spiders are not as active as the females of the wandering groups. They may not, indeed, be able to make way over the ground and among herbage with the same facility that marks the Saltigrades, Laterigrades, and Citigrades; but the activity in spinning work of the average female Orbweaver is simply enormous. One who has watched the method by which the great round webs of our common indigenous species are spun, will certainly agree that the operator is one of the most active of creatures in that department of work, at least. The rapidity. with which the threads are woven, the unceasing play of the hind legs in pulling out the thread, and the striding of the other limbs around the circle, together with the active exercise of the remaining organs, are evidences of immense vigor and activity. ‘The fact that such a large and intricate web as Hpeira spins can be wrought out in the course of half an hour or forty minutes, is proof enough of this activity. These snares will be reproduced several times a day if necessary, and the reproduc- tion continues day after day throughout the life-time of the aranead. “So also the same vitality of the female Orbweaver appears No. 3.] SEXUAL SELECTION IN SPIDERS. 127 in the construction of nests; which is not an inconsiderable work, involving no slight exercise of strength, as well as of ingenuity, as any one will see by turning to the chapter upon Nesting Habits, of this work, Chapter XVII, Volume I. “Again, this activity appears in the capture of prey. If any one will take his stand before an average orbweb of almost any common species, say Hpeira strix or Epeira scolpetaria, or Argiope cophinaria, at a season when flies and other insects abound, and in a site where they are plenty, he will be sur- prised at the intense activity displayed in the capture of insects. One after another these victims are seized, swathed, dragged to the hub or den to be devoured, and that with a display of ‘vigor in capturing, in swathing, in cutting out the captive, and repairing the web, which must strike the most casual observer. The feast will be left a number of times to seize and truss up in like manner other victims who happen to strike the snare, and on each successive capture the same tremendous rush and energy of action will be noticed. “T scarcely know a limit to the voracity of these Orbweaving spiders when full opportunity is given them to feed upon their natural prey; andI can certainly appeal to any one who has observed the actions referred to whether the whole demeanor of the aranead is not such as to impress him with the sense of a vast store of vitality and an almost exhaustless activity. Taking, then, the spinning work, and the ordinary action in capturing prey by means of nets as the standard, it cannot be affirmed with truthfulness that female Orbweavers are inac- tive, or that they suffer in respect of this element from com- parison either with the wandering tribes or with the males of their own species. “T might go further and say that when a female Orb- weaver is placed upon the leaves of a plant, or even upon the ground among the grasses, she will display an amount of activ- ity in getting from leaf to leaf, and limb to limb, and from point to point, which is surprising in a creature whose habits are so generally sedentary. I have often been amazed at the rapidity and facility with which the largest Orbweavers, as 128 PECKHAM. [Vol. 1, Argiope cophinaria and arygraspis, could make the circuit of a bush, or travel over a plane surface. “ As to the males of Orbweavers, generally, it is certainly not in accordance with my observations that they are more ac- tive than the females. On the contrary, I am disposed to think them rather lethargic and sluggish fellows. I am aware that it has been said, in corroboration of the theory that the female is more inactive than the male, that she will hang to the hub of her orb, or remain motionless within her tent, for hours and perhaps even days. It is true; but that action is quite as char- acteristic of the male as of the female. I have seen the males of Cophinaria, in attendance upon a female, hanging upon the outer courts of their lady love’s snare, apparently entirely inac- tive, for as much as two or three or four days in succession. They are very patient in their waiting, and make few move- ments during the courting period. “So also it may be said that those Orbweaver males, which spin webs that are as perfect after their kind as those of the fe- male, show precisely the same degree of patience in managing their snares and watching for the advent of insects as is shown by the female. “Tf we turn now to the wandering groups, and make comparison between the males and females of the species of these tribes, I am certain that it will be found that the females are as active as, or even more active than, the males. During certain seasons of the year, as, for example, when they are carrying their cocoons, they do indeed prepare for themselves a little cave or silken cell wherein they live until their young are hatched. But during that period, even, the Lycosids may be found running around upon the rocks and over the fields, drag- ging their egg-bag after them. When the young are hatched, it is not uncommon to observe the mother wandering over the fields with all her offspring piled upon her abdomen and the lower part of the cephalothorax—a strange, and, to most be- holders, a horrible sight, since the ordinary observer is not apt to associate the uncouth vision with the beautiful maternal devotion which the spider thus shows, and which has its No. 3.] SEXUAL SELECTION IN SPIDERS. 129 analogue in the human mother bearing her child in her arms or carrying it upon her bosom. Moreover, the excavating and fitting up these subterranean homes is a strong proof of a de- cidedly industrious character, and the act requires the exercise of great vigor, which, of course, is exclusively by the female. “As a matter of fact, therefore, 1 am compelled to think that among all wandering groups, the difference between the activity of male and female is certainly not in favor of the former. Whatever conclusions, therefore, are drawn from the belief that the male is possessed of greater activity and vital force than the female, must, in my judgment, be regarded as erroneous. ‘That he is more erratic in certain species, is true.” * In “Natural Selection” Mr. Wallace has brought out certain facts which are inconsistent with his present view. If the frequent superiority in the ornamentation of male birds arises from the fact that they have higher vitality than the females, how is it that in many families (including 1,200 species, or about one-seventh of all known birds+) we find the two sexes alike ornamented with brilliant colors and accessory plumes, which quite equal in beauty those of the male in those species where one sex alone is decorated? ‘These facts while comprehensible under his earlier supposition (that color is normal, and in these species is not kept down by natural selection since they build covered nests), find no explanation in his later theory of the higher vitality of the males. And, again, how shall we explain the fact that we often find the males in birds, insects and spiders as plainly colored as their mates, and this, too, when the habits of the two groups, the one plainly and the other brightly colored, are entirely similar? Mr. Pocock allows us to make the following quotation (from a letter of his) which bears on this subject, as showing that there is no relation between the activity of the males and their color: “The following case, with regard to which I can speak as an expert, seems to me to be rather against Mr. Wallace. * American Spiders and their Spinning Work, Volume II, pp. 7-72. 7 On Natural Selection, p. 244. 130 PECKHAM. [Vol. 1, Throughout the great group of Myriapoda, of which hundreds of specimens from all localities have passed through my hands, there is not a single case, so far as I know, of the sexes differing in color. And yet, many of the species, both of Diplopoda and Chilopoda, are very beautifully colored. Now, there is no scope in this group for the action of sexual selection, because if not entirely without eyes, none of the species (except perhaps Sentigera) can see to any appreciable extent. But if Wallace’s generalization with regard to-the greater vigor of the male be true, we should expect to find the males more beautiful than the females, quite irrespective of powers of vision. And that the males are more vigorous, at least in some cases, is shown by the fact that the males of two South African species of Spirostreptus, that I have in captivity, certainly excel the females in activity and amorousness—the last quality being, | should think, an unquestionable criterion of vital force. But these males only differ from the females in primary sexual features.” SECOND PART OF MR. WALLACE’S THEORY: CORRELATION OF HIGH VITALITY AND BRIGHT COLOR AMONG MALES. The second point in Mr. Wallace’s proposition is that those males that have the highest vitality have the most brilliant color. In “Tropical Nature” there are named six species of humming-birds in which there is a combination of unusual ac- tivity and pugnacity with brilliant color. Since there are four hundred and twenty-six species of humming-birds, a large pro- portion of which are brightly colored, this number is certainly very low. There are also adduced five cases of birds where the females are brighter than the males, in which “the males take charge of and incubate the eggs while the females are almost always larger and more pugnacious than the males. ” * Furthermore, Mr. Wallace, in “ Darwinism,” speaks of the or- namental plumes that arise not only in birds of paradise, but *Tropical Nature, p. 212. No. 3.] SEXUAL SELECTION IN SPIDERS. 131 also in many humming-birds and in some sun-birds and honey suckers, all of which are remarkable for their activity. This is surely a very small amount of evidence for so wide a generalization. The weak spot in the argument, however, ‘is not that Mr. Wallace gives but few instances of this combina- tion of color with activity, for He might easily have multiplied them ; but that he takes no notice of the numerous cases which are completely at variance with histheory.