Chapter 10 - Page 2

coupled, and one pair produced fertile ova. *(3) The Practical Entomologist, Philadelphia, vol. ii., May, 1867, p 88. *(4) Mr. Walsh, ibid., p. 107. *(5) Modern Classification of Insects, vol. ii., 1840, pp. 205, 206. Mr. Walsh, who called my attention to the double use of the jaws, says that he has repeatedly observed this fact.

The tarsi of the front-legs are dilated in many male beetles, or are furnished with broad cushions of hairs; and in many genera of water-beetles they are armed with a round flat sucker, so that the male may adhere to the slippery body of the female. It is a much more unusual circumstance that the females of some water-beetles (Dytiscus) have their elytra deeply grooved, and in Acilius sulcatus thickly set with hairs, as an aid to the male. The females of some other water-beetles (Hydroporus) have their elytra punctured for the same purpose.* In the male of Crabrocribrarius (see fig. 9), it is the tibia which is dilated into a broad horny plate, with minute membraneous dots, giving to it a singular appearance like that of a riddle.*(2) In the male of Penthe (a genus of beetles) a few of the middle joints of the antennae are dilated and furnished on the inferior surface with cushions of hair, exactly like those on the tarsi of the Carabidae, "and obviously for the same end." In male dragon-flies, "the appendages at the tip of the tail are modified in an almost infinite variety of curious patterns to enable them to embrace the neck of the female." Lastly, in the males of many insects, the legs are furnished with peculiar spines, knobs or spurs; or the whole leg is bowed or thickened, but this is by no means invariably a sexual character; or one pair, or all three pairs are elongated, sometimes to an extravagant length.*(3)

* We have here a curious and inexplicable case of dimorphism, for some of the females of four European species of Dysticus, and of certain species of Hydroporus, have their elytra smooth; and no intermediate gradations between the sulcated or punctured, and the quite smooth elytra have been observed. See Dr. H. Schaum, as quoted in the Zoologist, vols. v.-vi., 1847-48, p. 1896. Also Kirby and Spence, Introduction to Entomology, vol. iii., 1826, p. 305. *(2) Westwood, Modern Class., vol. ii., p. 193. The following statement about Penthe, and others in inverted commas, are taken from Mr. Walsh, Practical Entomologist, Philadelphia, vol. iii., p. 88. *(3) Kirby and Spence, Introduct. &c., vol. iii., pp. 332-336.

The sexes of many species in all the orders present differences, of which the meaning is not understood. One curious case is that of a beetle (see fig. 10), the male of which has left mandible much enlarged; so that the mouth is greatly distorted. In another carabidous beetle, Eurygnathus,* we have the case, unique as far as known to Mr. Wollaston, of the head of the female being much broader and larger, though in a variable degree, than that of the male. Any number of