Chap. X. 



INSECTS. 



o i o 



these organs for burrowing in sand-banks and making 

 their nests. 



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 (Hydro- 

 porus) have their elytra 

 punctured for the same ob- 

 ject. 6 In the male of Crabro 

 cribrarius (fig. 8.), it is the 

 tibia which is dilated into a 

 broad horny plate, with mi- 

 nute membraneous dots, giv- 

 ing to it a singular appear- 

 ance like that of a riddle. 7 

 In the male of Pen the (a 



genUS Of beetles) a few Of Fi S- 8. Crabro cribrarius. Upper figure 

 ,-. . , -,-, . . ' r.,1 male; lower figure, female. 



the middle joints ot the an- 



tennge are dilated and furnished on the inferior surface 



6 We have here a curious ana inexplicable cdse of dimorphism, for 

 some of the females of four European species of Dytiscus, and of certain 

 species of Iiydroporus, have their elytra smooth ; and no intermediate 

 gradations between sulcated or punctured "and quite smooth elytra 

 have been observed. See Dr. H. Schaum, as quoted in the ' Zoologist,' 

 vol. v.-vi. 1847-48, p. 1896. Also Kirby and Spence, ' Introduction to 

 Entomology/ vol. hi. 1826, p. 305. 



7 Westwood, 'Modern Class.' vol. ii. p. 193. The following state- 

 ment about Pentlie, and others in inverted commas, are taken from 

 Mr. Walsh, ' Practical Entomologist,' Philadelphia, vol. ii. p. 88. 



