542 EXTERNAL ANATOMY OF INSECTS. 



{Locusta F.) there are only two of these lines or ridges, 

 but notched or toothed ; and in some of the genus first 

 named only one a ; in Locusta Dux and affinities the^ro- 

 thorax has several transverse channels or rather folds b , 

 with corresponding ridges on its internal surface. 



6. With respect to the clothing of the prothorax, I have 

 not much to say : in Coleopterous insects this part is com- 

 monly naked; but in some genera, as Byrrhus, Anthrenus, 

 Dermestes, and many weevils [Curculio L.) it is partially 

 or totally covered with hairs or scales. In the other tho- 

 racic Orders it is usually naked, but in some Neuroptera, 

 the Myrmeleonina, &c, it is hairy; and in the Libellulina 

 it is fringed posteriorly with hairs. 



7. As to its relative proportions^ the prothorax is some- 

 times rather wider than the rest of the trunk and the 

 head, as in Onitis, Pasimachtis, &c; it is considerably nar- 

 rower in Collyuris and Odacantka; and of the same width 

 in those Scaritidce with striated elytra c . Again, it is 

 sometimes of the same width with the elytra, but wider 

 than the head, as in Hydrophilus, Dytiscus, &c. ; in some 

 instances it is of the same width with the head, and nar- 

 rower than the elytra, for instance in Anthia and Bra- 

 chinus. In most Coleoptera it is longer than the head 

 and shorter than the elytra ; but in Manticora, the vesi- 

 catory beetles, &c, it is shorter than either. In Gnoma 

 lo?igicollis d , it is nearly as long as the elytra; in many 

 Staphylinidce, Atractocerus, &c, longer ; in Phanceus car- 

 nifex, bellicosus, &c, it is longer than the elytra and the 

 rest of the body. With regard to itself, it is sometimes 



a Plate VIII. Fig. 10. b ibid. 



e Linn. Trans, vi. t, xxi./. 10, d Ihki. f. 8. 



