External anatomy or insects. 675 



with stiff bristles ; in Empis pennipes they are thickly 

 fringed on both sides; in Scarabceus M C L. only exter- 

 nally, and in Dytiscus serricornis internally ; in Necydalis 



• barpipes K. this fringe is longer at the apex ; and in Sa- 

 perda hirtipes Ol. the same tibice at that part are adorned 

 with a large brush, like that observable in the antennae 

 of some Lamice*. 



I must next call your attention to the teeth, spines, and 

 spurs with which the tibia of insects are sometimes armed. 

 With regard to teeth, you have doubtless often observed 

 those that distinguish the cubitus of the arm of most La- 

 mellicorn beetles : these vary in number from one, as in 

 Trox suberosus, to seven, as in Geotrupes autumnalis; but 

 the most universal number is three : in some species of 

 Geotrupes, as G. stercorarius, &c, the third tooth from 

 the apex, and those that follow it, may be called double. 

 These teeth, in their cubit or anterior shank, doubtless 

 assist these insects in burrowing. The four posterior 

 tibice in this tribe are also distinguished by a kind of teeth 

 which occupy their whole diameter, and resemble so 

 many steps. I have before noticed the remarkable cubit 

 of the Gryllotalpa, and likewise that of Scarites, Pasi- 

 machus, &c, in which some of the teeth are prolonged 

 into spines b , which are the next description of tibial arms 

 that I mentioned. Spines are of tivo kinds— those which 

 are merely processes of the crust of the tibia, and those that 

 are implanted, in it, and seem to have a gomphosis or per- 

 haps an amphiarthrosis articulation . An instance of the 



Jirst kind may be seen in the hind-legs of some grasshop- 



a Oliv. Ins. n. 68. t. i. /. 8. comp. n. 67. t. xii. /. 83. and Plate 

 XII. Fig. 25. a. b Vol. II. p. 365. and Plate XV. Fig. 5. 6. 



c See above, p. 433, Note b. and 404, Note a. 

 2x2 



