. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. 276 The Descent of Man. Part II. much, more unusual circumstance that the female of some water- beetles (Dytiscus) have their elytra deeply grooved, and in Acilius sidcatus 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 In the male of Crabro cribrarius (fig. 9), it is the tibia which is dilated into a broad horny plate, with minute mem- braneous dots, giving to it a sin- g
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. 276 The Descent of Man. Part II. much, more unusual circumstance that the female of some water- beetles (Dytiscus) have their elytra deeply grooved, and in Acilius sidcatus 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 In the male of Crabro cribrarius (fig. 9), it is the tibia which is dilated into a broad horny plate, with minute mem- braneous dots, giving to it a sin- gular appearance like that of a In the male of Penthe (a genus of beetles) a few of the middle joints of the antennse are dilated and furnished on the in- ferior surface with cushions of hair, exactly like those on the tarsi of the Carabidae, " and obviously for " the same ; In male dragon- flies, " the appendages at the tip " of the tail are modified in an " almost infinite variety of curious u patterns to enable them to em- " brace the neck of the ; Lastly, in the males of many in- sects, 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 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 (fig. 10), the male of which has the left mandible much, enlarged; so that the mouth is greatly distorted. In another Carabidous beetle, Eurygnathus,9 we have the case, 6 We have here a curious and ' Introduction to Entomology,' vol. inexplicable case of dimorphism, for iii. 1826, p. 305. some of the females of four Euro- 7 Westwood, 'Modern Class.' vol. pean species of Dytiscus, and of ii. p. 193. The following state- certain species of Hydroporus, have ment
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