292 The Descent of Man. Part 11 



each other after long intervals of time, and are deeply attached. 

 For instance, Pierre Huber, whose accuracy no one doubts, 

 separated some ants, and when, after an interval of four months, 

 they met others which had formerly belonged to the same 

 community, they recognised and caressed one another with their 

 antennae. Had they been strangers they would have fought 

 together. Again, when two communities engage in a battle, the 

 ants on the same side sometimes attack each other in the general 

 confusion, but they soon perceive their mistake, and the one ant 

 soothes the other.'' 



In this Order slight diffbiences in colour, according to sex, are 

 common, but conspicuous differences are rare except in the 

 family of Bees ; yet both sexes of certain groups are so brilliantly 

 coloured— for instance in Ohrysis, in which vermilion and 

 metallic greens prevail — that we are tempted to attribute the 

 result to sexual selection. In the Ichneumoiiidae, according to 

 Mr. Walsh,"' the males are almost universally lighter-coloured 

 than the females. On the other hand, in the Tenthredinidsa the 

 males are generally darker than the females. In the SirioidsB 

 the sexes frequently differ ; thus the male of Sirex juvencus is 

 banded with orange, whilst the female is dark purple ; but it is 

 difficult to say which sex is the more ornamented. In Tremex 

 eolumhm the female is much brighter-coloured 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 colour. 

 The males are generally the brighter, and in Bombus as well as in 

 Apathus, much more variable in colour than the females. In ' 

 Anthophora retusa the male is of a rich fulvous-brown, whilst 

 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-coloured than the males. Such differences in colour 

 can hardly be accounted for by the males being defenceless and 

 thus requiring protection, whilst the females are well defended 

 by their stings. H. MUUer,'" who has particularly attended to 

 the habits of bees, attributes these differences in colour in chief 

 part to sexual selection. That bees have a keen perception of 

 colour is certain. He says that the males search eagerly and 

 fight for the possession of the females ; and he accounts through 



»* P. Hobcr, ' Recherehes sur les Philadelphia,' 1866, pp. 2.S8-239. 

 Mceurs des Foivrmis,' 1810, pp. 150, "° ' Anwendung der Darwinschen 



165. Lehre auf Bienen.' Verb, d, n. 



" ' Prot Entomc-og. Soc. of Jahrg. xxii. 



