174 



THE AMERICAN NATURALIST [Vol. XLIV 



young of both sexes more closely resemble the adult 

 female; (b) when the adult female is more conspicuous 

 than the adult male, the young of both sexes more closely 

 resemble the adult male; and (c) when both adults are 

 alike the young of both sexes resemble them. 



3. Characters of value after the act of sex-recognition 

 to insure efficient mating would seem to be various, and all 

 probably perpetuated by natural selection. Such would 

 be the relatively larger legs in the case of certain males, 

 in so far as they serve to hold the female. Smaller size 

 and greater agility of the male, not a frequent phenom- 

 enon in araneads, would also aid in the mating by ena- 

 bling the male to move more quickly upon the snare of the 

 female, and to escape more rapidly from her should she 

 be aggressive. 



4. Characters of value in providing for and nurturing 

 the young are limited in spiders to the female, and are 

 also perpetuated by natural selection. Such are the 

 greater size of the abdomen to accommodate the eggs, and 

 the gland whose function is to agglutinate them. Such is 

 also .the greater pugnacity and bravery of the female, 

 which is probably the expression of her greater need of 

 food. 



5. Characters due to habitudinal sex differences are 

 few in spiders. Such differences first become marked at 

 maturity, as do the other secondary sexual characters, 

 all being in some way connected with internal secretions 

 formed during the elaboration of the genital products. 

 Tn the epeirids, as shown by me (19086), immature males 

 have the same mode of life as their sisters, and " construct 

 oerfect snares of the types of those of their respective 

 females. But the adult males ... do not spin snares at 

 all, but build nests near those of adult females. ' ' Indeed, 

 it is quite general among snare-making species that adult 

 eager males regularly leave their snares to live upon or 

 near those of females; and adult males of lycosids and 

 drassids, which make no snares, leave their nests to seek 

 for females. The chief habitudinal difference, accord- 

 ingly, is that while the female continues a more or less 



