which are much larger than those of the female, for the same purpose,
but probably likewise for fighting. In one of the sand-wasps
(Ammophila) the jaws in the two sexes are closely alike, but are used
for widely different purposes: the males, as Professor Westwood
observes, are exceedingly ardent, seizing their partners round the
neck with their sickle-shaped jaws (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.); whilst the females use these organs for burrowing
in sand-banks and making their nests.
[Fig. 9. Crabro cribrarius. Upper figure, male; lower figure, female.]
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. (6. We have here a curious and inexplicable case of
dimorphism, for some of the females of four European species of
Dytiscus, 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.) In the male of Crabro cribrarius (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. (7. 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.) 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
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