Chap. X. 
HYMENOPTERA. 
365 
mind that insects belonging to this Order have the 
power of recognising 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 mutually recognised and caressed each 
other with their antennae. Had they been strangers 
they would have fought together. Again, when tw r o 
communities engage in a battle, the ants on the same 
side in the general confusion sometimes attack each 
other, but they soon perceive their mistake, and the 
one ant soothes the other . 55 
In this Order slight differences in colour, according 
to sex, are common, but conspicuous differences are 
rare except in the family of JBees; yet both sexes of 
certain groups are so brilliantly coloured— for instance 
in Chrysis, in which vermilion and metallic greens 
prevail — that we are tempted to attribute the result 
to sexual selection. In the Ichneumonidse, according to 
Mr. Walsh , 56 the males are almost universally lighter 
coloured than the females. On the other hand, in the 
Tenthredinidse the males are generally darker than the 
females. In the Siricidao 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 most ornamented. In Tremex 
columbsQ the female is much brighter coloured than the 
male. With ants, as I am informed by Mr. F. Smith, 
the males of several species are black, the females 
being testaceous. In the family of Bees, especially in 
55 P. Huber, 4 Reclierches sur les Moeurs des Fourmis,’ 1810, p. 150, 
165. 
56 4 Proc. Entomolog. Soc. of Philadelphia,’ 1866, p. 238-239. 
