EXTERNAL ANATOMY OF INSECTS. 557 



dorsolum, and in some (Tetyra F.) covering the whole 

 abdomen, as well as the Hemelytra and the wings ; it is 

 most commonly, as in the Coleoptera, obtriangular a , but 

 in the last-mentioned genus it often approaches to a pen- 

 tagonal shape. Though usually so striking a feature in 

 this tribe, in the aquatic bugs (Gerris &c.) it is covered 

 by the prothorax. In some species of Reduvius F. (R. 

 biguttatus, mutillarius, lugens, &c.) it is armed with one 

 or more dorsal or terminal spines. In the Homopterous 

 section, where the dorsolum, as in Tettigonia F., is not 

 covered by the prothorax, the scutellum, which is merely 

 a continuation of that part, bears some resemblance to a 

 St. Andrew's cross, and terminates in a fork b ; in Ful- 

 gora, in which it is partly covered, it is merely the trian- 

 gular point of the dorsolum ; in the Cercopidce, &c, whose 

 dorsolum is wholly covered, the triangular scutellum is 

 distinct from it ; in Centrotus, Damis, and Membracis, in 

 which the prothorax is producted, and covers the abdo- 

 men more or less, the scutellum is a short transverse di- 

 stinct piece. In the Lepidoptera, from the difficulty of 

 abrading sufficiently the scales and hairs without injury, 

 it is difficult to obtain a correct idea of the part in ques- 

 tion ; in the cabbage butterfly (Pieris Brassicce) it ap- 

 pears to be triangular : in the humming-bird hawk- 

 moth (Macro-glossum Stellatarum) it approaches to a 

 rhomboidal shape c ; and in the eggar-moth (Lasiocampa 

 Quercus) it is completely rhomboidal. In the Libellu- 

 lina, in the Neuroptera Order, it seems to be represented 

 by the posterior point of the dorsolum, which terminates 



■ Plate VIII. Fig. 20. k' . b Ibid. Fig. 16. k'. 



- Plate IX. Fig. 1. //. N. B. This is from Cossus F. 



