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Show 364 SEXU.A.JJ SELECTION. PART II. invariably females. This is probably a case of reversion, for in the true Libellu1ro, when the sexes differ ]n colom·, the females are always orange or yellow, so that supposing Agrion to be descended from some primordial form having the characteristic sexual colours of the typical Libellulro, it would not be surprising that a tendency to vary in this manner should occur in the females alone. Although many dragon-flies are such large, powerful, and fierce insects, the males have not been observed by Mr. MacLachlan to ~ght together, except, as be believes, in the case of some of the smaller species of Agrion. In another very distinct group in this Order, namely in the Termites or white ants, both sexes at the time of swarming may be seen running about, "the "male after the female, sometimes two chasing one " female, and contending with great eagerness who shall " win the prize." o~ Order, Hymenoptera.-Tbat inimitable observer, lH. F abre,53 in describing the habits of Oerceris, a wasplike insect, remarks that " fights frequently ensue "between the males for the possession of some parti" cular female, who sits an apparently unconcerned "beholder of the struggle for supremacy, and when the " victory is decided, quietly flies away in company " with the conqueror." 'Vestwoocl 54 says that the males of one of the saw-flies (Tenthredinre) "have been " found fighting together, with their mandibles locked." As M. Fabre speaks of the males of Oerceris striving to obtain a particular female, it may be well to bear in 52 Kirby nnd Spence, ' Introduct. to Entomology,' vo1. ii. 1818, p. 35. j J See an interesting article, " The 'Writings of Fabre," in' Nat. Hist. Review,' April, 1862, p. 122. 54 'Joumal of Proc. of Entomolog. Soc.' Sept. 7th, 1863, p. 160. CHAP. X. HYl\IENOPTERA. 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 antennre. Had they been strangers they would have fought together. Again, when two communities engage in a battle, the ants on the same side in the general confusion sometimes attack each other, but they soon perceive their mistc<tke, and the one ant soothes the other.o~ In this Order slight differences in colour accordin()' ' 0 to sex, are common, but conspicuous differences are rare .except in the family of Bees ; yet both sexes of certam groups are so brilliantly coloured-for instance in O~rysis, in which vermilion and metallic greens prevail-that we are tempted to attribute the result to sexual selection. In the Ichneumonidre, according to Mr. vValsh,56 the males are almost universally lighter coloured than the females. On the other hand in the Tentbredinidre the males are generally darker than the females. In the s.iricic~re the sexes frequently differ; th~s the male of S~rex J1-tvencus is banded with orange, whilst the female Is dark purple; but it is difficult to say which sex is the most ornamented. In Tremex columbm the female is much brighter coloured than the male. 'Vith ants, as I am informed by 1\ir. F. Smith, th~ males of several species are black, the females bemg testaceous. In the family of Bees, especially in 5;; P. Huber, 'Recherches sur les Moours des Fourmis' 1810 p 150 165. ' ' . ' 66 'Proc. Entomolog. Soc. of Philadelphia,' 186G, p. 238-239. |