502 EXTERNAL ANATOMY OF INSECTS. 



ovate, as in other bees (Andrena F.); triangular, as in the 

 water-boatman (Notonecta). They are also often oblong, 

 and occasionally narrow and linear ; as in that singu- 

 lar beetle Helceus. In many of the Muscidce they form 

 nearly a semicircle, or rather, perhaps, the quadrant of a 

 sphere. The eyes of the Capricorn-beetles ( Cerambyx L.) 

 have a sinus on their inner side, as it were, taken out of 

 them ; so that they more than half surround the anten- 

 nae, before which is the longest portion of them. An 

 approach to this shape is mote or less observed in the 

 darkling-beetles (Tenebrio L.); but in these the sinus is 

 not so deep. I may under this head observe, that in 

 those Ma ntidce that represent dry leaves, and some others, 

 these organs usually terminate in a spine a . 



Though not distinguished by the beauty and anima- 

 tion that give such interest to the eye of vertebrate ani- 

 mals, and exhibiting no trace of iris or pupil, yet from 

 the variety of their colours the compound eyes of insects, 

 though most commonly black or brown, are often very 

 striking. Look at those of one of the lace-winged flies 

 that commit such havoc amongst the Aphides b , and it 

 will dazzle you with the splendour of the purest gold, 

 sometimes softened with a lovely green. The lenses of 

 those of Xenos blaze like diamonds set in jet c . You 

 have often noticed the fiery eyes of many horse-flies 

 (Tabanusl^.) with vivid bands of purple and green d . 

 Others are spotted e ; and Schellenberg has figured one 

 ( Thereva hemiptera) f , that exhibits the figure of a flower 



a Stoll Spectres, &c. t. iv.f. 14. t. x.f. 38, &c. 



b Vol. I. p. 261 — . e Linn. Trans, nhi supr. 



d Schellenberg Mouches, L xxvii.f. 1, 2.n,d. 



e Ibid. t. ix./. 3. a. < Ibid, t ii./. 2. a. 



