No. 1.] 



SEXUAL SELECTION IN SPIDERS. 



19 



well established. If we may add to these a large number of 

 bright-colored, undescribed species from our own Guatemala 

 collection, in which the young closely resemble the female, the 

 generalization is materially strenghtened. 



In order to estimate to what extent the sexes differ in the 

 Attidse, we tabulated the species, in a number of works, giving 

 the number of species in which both sexes, and also the num- 

 ber in which one only are described. If it may be assumed 

 that a collector ordinarily takes as many of one sex as of the 

 other — and our numerous collections from different parts of the 

 world confirm this supposition^ — if the sexes were fairly alike 

 they would be identified as one species and placed together ; if, 

 on the contrary, the sexual differences were great (the habits 

 being unknown) many species would be founded on a single 

 sex. 



TABLE OP SPECIES DESCBIBED BT DIFFERENT AUTHORS, ACOOEDING 

 TO SEX. TOTAL 930. 



Koch, and Keyserling . 

 Taczanowski 



C.Kocli J 



Cambridge 



Lucas 



ThoreU -j 



Simon 



"Walckenaer - 



Peckham 



Simon 



Vinson 



LOCALITY. 



Australia 



South America 



World, except N. Am. and / 



Europe ) 



Various 



Algiers 



Burmah and Indian Archi- ( 



pelago ) 



Various places, not France. . , 

 World, except N. Am. and ) 



Europe. . . • ) 



North America 



France 



Madagascar, Mauritius, etc. . 



16 

 36 



42 



22 



17 



21 

 11 



The table shows that in a total of 930 species from all parts 

 of the world the single males just about balance the single 



1 That this is not always true in other families is shown by Stollczka, who says : 

 "In collecting Epeirldm I was particularly struck with the very great scarcity of male 

 specimens ; for, among about 200 specimens belonging to about thirty species, there 

 were not more than five or six males." Indian Arachnida, Proo. Asiat. Soc, Vol. 

 XXXVni, p. 2;h. This was probably due to his having collected either before or after 

 the mating season, when the males are always more rare. 



