336 THE DESCENT OF MAN 



■with certain species (Attalia) bred by him, tbe males were 

 to tlie females as six to one; while exactly the reverse oc- 

 curred with the mature insects of the same species caught 

 in the fields. In the family of Bees, Hermann Miiller" col- 

 lected a large number of specimens of many species, and 

 reared others from the cocoons, and counted the sexes. He 

 found that the males of some species greatly exceeded the 

 females in number; in others the reverse occurred; and in 

 others the two sexes were nearly equal. But as in most 

 cases the males emerge from the cocoons before the females, 

 they are at the commencement of the breeding season prac- 

 tically in excess. Miiller also observed that the relative 

 number of the two sexes in some species differed much 

 in different localities. But as H. Miiller has himself re- 

 marked to me, these remarks must be received with some 

 caution, as one sex might more easily escape observation 

 than the other. Thus his brother, Fritz Miiller, has noticed 

 in Brazil that the two sexes of the same species of bee some- 

 times frequent different kinds of .flowers. With respect to 

 the Orthoptera, I know hardly anything about the relative 

 number of the sexes; Korte,*' however, says that, out 

 of 500 locusts which he examined, the males were to the 

 females as five to six. With the Neuroptera, Mr. Walsh 

 states that in many, but by no means in all the species of 

 the Odonatous group, there is a great overplus of males; 

 in the genus Hetaerina, also, the males are generally at least 

 four times as numerous as the females. In certain species 

 in the genus Gomphus the males are eqiially in excess, 

 while in two other species the females are twice or thrice 

 as numerous as the males. In .some European species of 

 Psocus thousands of females may be collected without a 

 single male, while with other species of the same genus 

 both sexes are common. °° In England, Mr. MacLachlan 



*' "Anwendung der Darwin'schen Lehre," "Verli. d. n. V. Jahrg." xxiv. 

 88 "Die Strich, Zug oder 'Wanderlieusclireoke," 1828, p. 20. 

 8' "Observations on N. American Neuroptera," by H. Hagen and B. D. 

 Walsh, "Proc. Ent Soc. PMadelpliia, " Oct. 1863, pp. 168, 223, 239. 



