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Show :3GG SEXUAL SELEC'flON. PART II. the solitary species, as I hear from th~ sa1~1e distin. ·guished entomologist, the sexes often dtffer. m colour. rrhe males are generally the brightest, ~nd m. Bombus as well as in Apathus, much more vanable m col01~r than the females. In Anthophora retusa the. male. IS -of a rich fulvous-brown, whilst the female 1s qmte black: so are the females of several species ofX~locopa, the males being bright yellow. In an Austraha_n .bee (Lestis bombylans), the female i~ of ~n .extremely bnll1ant steel-blue, sometimes tinted w1th vivid g~·een .; the male b em· g of a brioo -ht brassy colour clothed With riCh fulv'do us1 pu b escence. As in this group the .f emale.s are. prov.i ee.L with excellent defensive weapons m the~r sti~gs, It IS not probable that they have come to_ drffer m colour from the males for the sake of protectwn. Mutilla Europrea emits a stridulating noise; and ac-cording to Goureau 57 both sexes have this pow~r. He .attributes the sound to the friction of the thu·d and preceding abdominal segments ; and I find t?at .these ·surfaces are marked with very fine concentnc ridges, ·but so is the projecting thoracic collar, on which ~he head articulates; and this collar, when scratched wit~ the point of a needle, emits the proper sound. It IS rather surprising that both sexes . sho~lcl have the power of stridulating, as the male 1s wmged and the female wingless. It is notorious that Bees expre~s ·eertain emotions, as of anger, by the tone of their humming, as do some dipterous insects; but I have not referred to these sounds, as they are not known to be in any way connected with the act of courtship. Order, Coleoptera (Beetles). - 1\fany bee~les are ,coloured so as to resemble the surfaces whiCh they o7 Quoted by Westwood, 'Modern Class. of Insects,' vol. ii. p. 21!. .C:rAI'. X. COLEOPTERA. 3G7 habitually frequent. Other species are ornamented ·with gorgeous metallic tints,-for instance, many Carabidre, which live on the ground and have the power of defending themselves by an intensely acrid secretion, -the splendid diamond-beetles which are protected by an extremely hard covering,-many species of Chrysomela, such as 0. cerealis, a large species beautifully striped with various colours, and in Britain confined to the bare summit of Snowdon,-and a host of other species. These splendid colours, which are often .arranged in stripes, spots, crosses and other elegant patterns, can hardly be beneficial, as a protection, except in the case of some flower-feeding species; and we cannot believe that they are purposeless. Hence the suspicion arises, that they serve as a sexual attraction; but we have no evidence on this head, for the sexes rarely differ in colour. Blind beetles, which cannot of ~ourse behold each other's beauty, never exhibit, as I hear from lVIr. Waterhouse, jun., bright colours, though they often have polished coats: but the explanation of their obscurity may be that blind insects inhabit caves .and other obscure stations. Some Longicorns, however, especially certain Prionidre, ofi'er an excep6on to the common rule that the sexes of beetles do not differ in colour. J\fost of these insects are large and splendidly coloured. The males in the genus Pyrodes,58 as I saw in Mr. Bates' collection, are 58 Pyrod~s pulcherrimus, in which the sexes differ conspicuously, has ~en descnbed by Mr. Bates in 'Transac·t. Ent. Soc.' 1869, p. 50. I will specify the few other cases in whic:h I have heard of a difference in colour between the sexes of beetles. Kirby and Spence (' Introduct. to Entomology,' vol. iii. p. 301) mention a Cantharis, Meloe, Rbagium, and the Leptum testacea ; the male of the latter being testaceous, with 1.1. black thorax, and the female of a dull red all over. These two latter beetles belong to the Order of Longicorns. Messrs. R. Trirnen .and Waterhouse, junr., inform me of two Lamellicorns, viz., a Peri- |