No. 2.] PROTECTIVE RESEMBLANCES IN SPIDERS. 99 



lacking to the males, because long life in the females is of 

 greater importance to the species than long life in the males.* 



This applies also to the Gasteracanthidaa where the females 

 are much larger, much more inedible, and much more conspic- 

 uous than the males. Wallace, however, limits his proposition 

 to cases where the modification is for concealment, and illustrates 

 it by instances among butterflies where the female alone mimics 

 some nauseous species. The Gasteracanthidse are an exception 

 to his rule, that in groups which have a protection of any kind 

 independent of concealment, sexual differences of color are 

 either quite wanting or slightly developed. f That I do not 

 misinterpret his meaning is shown by the fact that after stating 

 this rule he goes on to enumerate several cases in which specially 

 protected species have the sexes almost or quite alike. 



In Gasteracantha and Acrosoma the habits of the female 

 as well as her functional importance call for some special 

 protection. She is much exposed, remaining in her web all the 

 time, while the male passes most of his life in concealment. 

 Thus the female of A. spinea, though not so gaudily colored as 

 many others, is easily recognized, and is constantly seen on low 

 bushes during the summer. At about the first of August the 

 males appear, quite suddenly and in large numbers, and may 

 be seen running about the leaves and branches near the webs 

 of the females. Toward the end of the month they disappear. 

 Acrosoma and Gasteracantha are so near together that this 

 tends to prove the correctness of Cambridge's surmise that the 

 males of the latter genus are short-lived. J 



* " The comparative importance of the sexes varies much in different classes of 

 animals. In the higher vertebrates, where the number of young produced at a birth is 

 small and the same individuals breed many years in succession, the preservation of 

 both sexes is almost equally important. * * * In insects the case is very different; 

 They pair but once in their lives, and the prolonged existence of the males is In most 

 cases quite unnecessary for the continuance of the race. The female, however, must 

 continue to exist long enough to deposit her eggs in a place adapted for the develop- 

 ment and growth of her progeny. Hence there is a wide difference in the need for 

 protection in the two sexes ; and we should therefore expect to find that in some cases 

 the special protection given to the female was in the male less in amount or altogether 

 wanting." A- R. Wallace, Watufal Selection, p. 112. 



t Loc. cit, p. 113. 



{This shortness of life is common in the males of the Attlds. In several spe- 

 cies it is almost impossible to find the male, which is very common earlier In the 

 season, after the first of August, although the females are still numerous. 



