26 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



words, the female is twenty times as long and thirteen hundred times as 

 heavy as her partner.^ Dr. Vinson ^ strikingly represents this disparity 

 of size in the species Nephila nigra (Vinson), which is here presented, 

 (Fig. 6), with both sexes natural size. A full grown female of our Basket 

 Argiope bears about the relative laroportion to the size of her male, of a 

 horse to a large dog. The largest female Argiope measures in body length 

 one inch, in spread of legs three inches. Her abdomen is thick in pro- 

 portion. A male has a body length of one-fourth inch, the spread of legs 

 being one inch and a quarter. Fig. 14 will show the relative body lengths 

 and sizes of the sexes of Argiope cophinaria. 



This disproportion, however, in the size of the sexes is not universal. In 

 some species, as will be found by a reference to the plates in Volume III., tlie 

 difference is slight, and, indeed, is sometimes on the side of the male, even 

 among Orbweavers, as in the case of Ei^eira strix. Moreover, the males 

 have relatively longer and apparently more powerful legs than the female. 

 The increased length must be serviceable in the preliminary courtship, 

 when the males stand off and solicit or test the feeling of 

 their mates by touclies of the fore feet. These features are 

 also beneficial in clasping their mates during amatory em- 

 brace, and must add to their muscular vigor both in conflict 

 and retreat. This difference in tlie legs, I have no doubt, 

 fully compensates for difference in body size in the case of 

 many species. Especially is this true in the case of the Wan- 

 derers, with the exception, perliaps, of some of the Thom- 

 isoids. Moreover, the legs of some Orbweavers are armed 

 with formidable weapons in rows of strong spines arranged 

 Fig. 7. Tibial spines, aloug the iuucr surfacc of the tibia. (Fig. 7, Tibial spines 

 (After Emerton.) ^f Epeira domiciUoruni, a, and Epeira trivittata, b.) 



There is also a difference in size among the individuals of any one 



species. I have found females (Epeira vertebrata) quite mature, making 



cocoons, who were scarcely more than half as large as others of 



Size Va- ^-j^g same species, and to some extent a like difference prevails 



nation m j^^ ^j^^ ^.^^^ ^^ ^^^ ^^^^^^, ^^^ j^ ^^^^^ readily occur, therefore. 



Species that a large male and a small female will come together, and 

 thus, in point of strength, be placed more nearly upon an equal- 

 ity, or even give the preponderance to the male. In such a case his oppor- 

 tunity for feeding upon his partner is quite as good as hers. For these 

 reasons I am disposed to think that the perils of courtship depend, first, 

 upon the relative size of the individuals, and, second, upon the chances 

 of arousing the voracious appetite of one or the other partner by unusual 

 movements. In other and ordinary cases. Nature provides a sentiment 



' Cambridge, "Spiders of Dorset," introduction, page xxvii. 

 ' Spiders of Reunion, IMauriee, and IMadagascar, PI. VI. 



