No. 1.] SEXUAL SELECTION IN SPIDERS. 15 



looking over systematic works we unfortunately obtain little or 

 no information about the moulting habits of spiders. Most of 

 the species have been described by workers living in the large 

 cities of Europe, from collections coming to them from distant 

 parts of the world, so that an observation of habits was impos- 

 sible. Then, too, such collections contain only adult or nearly 

 adult forms, since both systematists and collectors have thus 

 far given their attention only to these. There are, therefore, 

 accessible on this subject, little more than the impressions of 

 several high authorities in arachnology as published by Darwin. 

 For some years past we have been accumulating data as to the 

 differences in form and color between the young and the adults, 

 and also between the two sexes in the adult stage in the same 

 species. 



Before giving the facts that we have thus far obtained it 

 may be well to remind our readers that spiders, shortly after 

 hatching, cast the skin, and that this moulting of the integu- 

 ment, including the outer coat of the eyes, is repeated, the 

 number of times varying in the different species and possibly 

 in the two sexes. It is probable that the Atlidse moult from 

 seven to eleven times before reaching maturity. In Dendry- 

 phantes capitatus we have counted ten moults and the spider was 

 still immature. If one examines any of our spiders soon after 

 they are hatched he will verify Dr. McCook's generalization 

 that " the color of young spiders is almost without exception 

 bright yellow or green, whitish or livid.'" Soon after this stage, 

 probably at the third or fourth moult, colors appear, distrib- 

 uted in patterns characteristic of the species, and as the spiders 

 continue to advance in age and make their successive moults, 

 still other and more marked changes may be noted. 



Let us now pass to the consideration of the classes of cases 

 under which the differences and resemblances, in color and 

 form, between the young spiders and the adults of one or both 

 sexes may be arranged. It is true among spiders as among 

 birds, that the several classes pass into each other ; and that 



1 Proc. Acad, of Nat. Sci. of Phila., 1888, p. 172. 



