INSECTS. 331 



times attack each other in the general confusion, hut they 

 soon perceive their mistake, and the one ant soothes the 

 other. * 



In this order slight differences in color, according to sex, 

 are common, hut conspicuous differences are rare except in 

 the family of bees; yet both sexes of certain gi'oups are so 

 brilliantly colored for instance in Chrysis, in which ver- 

 milion and metallic greens prevail that we are tempted to 

 attribute the result to sexual selection. In the Ichneu- 

 monidae, according to Mr. Walsh, f the males are almost 

 universally lighter-colored than the females. On the other 

 hand, in the Tenthredinidae the males are generally darker 

 than the females. In the Siricidae the sexes frequently 

 differ; thus the male of Sir ex jnvencus is banded with 

 orange, while the female is dark purple; but it is difficult 

 to say which sex is the more ornamented. In Tremex 

 columhcB the female is much brighter colored than the 

 male. I am informed by Mr. F. Smith that the male 

 ants of several species are black, the females being 

 testaceous. 



In the family of bees, especially in the solitary species, 

 as I hear from the same entomologist, the sexes often differ 

 in color. The males are generally the brighter, and in 

 Bombus as well as in Apathus, much more variable in color 

 than the females. In Anthopliora retusa the male is of a 

 rich fulvous-brown, while the female is quite black; so are 

 the females of several species of Xylocopa, the males being 

 bright yellow. On the other hand the females of some 

 species, as of Andrcena fulva, are much brighter colored 

 than the males. Such differences in color can hardly be 

 accounted for by the males being defenseless and thus 

 requiring protection, w^hile the females are well defended 

 by their stings. H. Miiller,]; who has particularly attended 

 to the habits of bees, attributes these differences in color in 

 chief part to sexual selection. That bees have a keen per- 

 ception of color is certain. He says that the males search 

 eagerly and fight for the possession of the females; and he 



*P. Huber, " Recherches sur les Moeurs des Fourmis," 1810, pp. 

 150, 165. 



t ' Proc. Entomolog. Soc. of Philadelphia," 1866, pp. 238, 239. 



X " Anwendung der Darwinschen Lehre auf Bienen," Verh. d. n. 

 Jahrg., xxix. 



