. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. INSECTS. 313 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 (Dytis- cus) 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 Crabr
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. INSECTS. 313 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 (Dytis- cus) 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 Crabro crihrarms (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, f In the male of Penthe (a genus of beetles) a few of the middle joints of the antenn83 are dilated and furnished on the inferior surface with cushions of hair^ ex- actly like those on the tarsi of the CarabidaG, ^"^and obviously for the same end/^ In tnale dragon-flies, ^^the appendages at the tip of the tail are modified in an almost in- finite 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 thick- ened, but this is by no means invariably a sexual character; or one pair, or all three pairs are elongated^ sometimes to an extrava- gant length. J ji' The sexes of many species in all the orders L present differences, of which the meaning is inut understood. One curious case is. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York : A. L. Burt
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
