SEXUAL SELECTION 883 



says that tte males of one of the saw-flies (Tenthredinge) 

 •'have been found fighting together, with their mandibles 

 locked." As M. Fabre speaks of the males of Cerceris 

 striving to obtain a particular female, it may be well to 

 bear in mind that insects belonging to this Order have 

 the power of recognizing 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 

 recognized 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 differences in color, 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 colored — for instance in Chrysis, in which 

 vermilion and metallic greens prevail — that we are tempted 

 to attribute the result to sexual selection. In the Ichneu- 

 monidse, according to Mr. Walsh, *' the males are almost 

 universally lighter-colored than the females. On the other 

 hand, in the Tenthredinidse the males are generally darker 

 than the females. In the Siricidse the sexes frequently 

 differ; thus the male of Sirex juvencus is banded with 

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

 to say which sex is the more ornamented. In Tremex 

 eolumboB 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, ia 



^ p. Huber, "Reoherches sur les McEure des Fourmis," 1810, pp. 160, 16&, 

 »» "Proe. Satomolog. Soc. of Philadelphia," 1866, pp. 238-239. 



