106 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Peck- 

 ham's 

 Studies. 

 Attidee. 



valuable and interesting. He concludes that when the adult male is 

 more conspicuous than the adult female, the young of both sexes 

 closely resemble the latter in form and color. On the contrary, 

 when the female is more conspicuous the young follow the more 

 modest colors of the male, especially in the earlier moults. 

 When the adult sexes resemble one another the young of both 

 sexes favor the common type. 



As examples of the above, Phidippus johnsonii female has the abdomen 

 red and black, with a white base and some white dots ; the male is bright 

 vermilion red, with sometimes a white band at the base. The young of 

 both sexes resemble the less showy mother until the last moult, when the 

 males assume their bright livery. 



In another species, Habrocestum splendens, which the Peckhams illus- 

 trate with a good plate, the young during the first moults more closely 

 resemble the female, which is the less showy sex. The male is a brilliant 

 fellow, who dons his gorgeous livery at the last moult just as he becomes 

 mature, though in some species the nuptial robe is acquired one moult 

 before maturity. 



Among the Laterigrades the same rule obtains, several species of 



Thomisids showing greater brilliancy of color among the adult males, 



while the young males resemble the female until the last moult. 



T fltftTl 



, In Sparassus smaragdalus 1 the female lias a deep green body and 



legs of somewhat lighter shade ; the male 2 lias green corselet and 



legs, but the entire dorsum of the abdomen yellow, with a wide herring 



bone median stripe of red and the folium margined on each side with the 



same color. The young at the first moult are a 

 dull whity-yellow color and grayish legs, but in 

 subsequent moults are said to resemble the mother. 

 Figs. 65 and 66 will illustrate the difference 

 resulting from the final moult of male spiders 

 generally. The drawings are made from a male 

 Zilla atrica, Fig. 65 being the form shortly before 

 the last moult and Fig. 66 that of the mature 

 male. In some species the difference between ma- 



FIG. 65. FIG. 66. , . . , ., . 



ture and immature palps is much more striking. 



FIG. 65. Immature male palp of 



Zilla atrica. Flo. 66. The same 

 when mature. 



It is not correct to say that these modifica- 

 tions are effected in the interval of the last moult 

 alone. In point of fact the distinctions begin to appear earlier, but they 

 are commonly so difficult to detect, and the apparent change effected during 



1 A fine female of this species with her cocoon and young was taken by Rev. W. F. 

 Anderson, of Fordham, N. Y., on the mountains of Switzerland and brought to America 

 safely. It was sent to me alive and lived several weeks. The young were all a dull yellow- 

 ish color with livid legs, but I could not preserve them beyond the first moult. 



2 Blackwall, Spiders Gt. B. & I., Vol. II., pi. v., Fig. 61. 



