62 EXTERNAL ANATOMY OF INSECTS. 



form the lateral regions of the scull. Besides these compound 

 eyes, insects have generally two or three ocelli, or simple eyes. 

 These, like the true eyes, are firmly fixed in the skull, and 

 are alike incapable of being separated from it without fracture. 

 The simple eyes are situated usually on the crown of the 

 head; their number is generally, in Lepidoplera, two; in 

 Dlptera, three ; in Hymenoptera, three ; in Coleoptera, 

 none ; b in Orthoptera, three ; in Hem'iptera, two. With 

 the exception of the compound and simple eyes, the skull is 

 a single, continuous, and undivided piece. Entomologists 

 have endeavoured to assign names to the different regions of 

 the skull, but have hitherto been unable to establish them. It 

 cannot be too frequently or too emphatically repeated, that 

 names of parts having unfixed limits are objectionable, as 

 leading to confusion. An author might establish his nomen- 

 clature from a single species, provided inquiry was directed to 

 that species alone. The anatomy of a beetle's or locust's 

 skull gives us scarcely any idea of that of a butterfly's. A 

 nomenclature well adapted to the skull of a cockchafer would 

 be useless for that of a dragon-fly. Fabricius describes no parts 

 but the forehead, clypeus, throat, and simple and compound 

 eyes. Latreille, Burmeister, and many others, recapitulate 

 the labours of preceding writers. Desvoidy is original, precise, 

 and clear, but his nomenclature is adapted solely to Dipteral 



b In the fourth number of Germar and Zincken Sommer's Magazine, it is 

 affirmed, that they are discoverable in Gravenhorst's genus Omalium, but not in 

 the kindred genera Micropepius and Anthophagus. Upon examining the former 

 genus, I find, that although Omalium planum and affinities, 0. Siriatuliim, and some 

 others, appear not to have them, yet with the aid of a good magnifier they may 

 be discovered in most species of that genus, as likewise in Evasthetits. 1 find 

 them also very conspicuous in A. Caraboides and other Anthophagi, but some- 

 species appear to want them. — Kirby. 



On a pretend u que les Anthophagus, les Omalium et les Paussus avaient de 

 ces yeux simples ; mais j'avoue que je n'ai jamais pu les apercevoir. — Straus- 

 D'drc/cheim. 



c La tete offre six regions principales : le front ; la face ; la region inferieure; 

 la region posterieure : les yeux forment les deux regions laterales. 1. Le front 

 (from) ou la region frontale, s'etend de la partie posterieure de la tete, a la base 

 des antennes, et d'un ceil a Fautre ceil. II se divise en trois parties. La partie 

 la plus posterieure, et celle qui ordinairement a le moins d'etendue est situee 

 derriere les stemmates, et porte le nom de vertex {vertex.) La partie stemma- 

 tique, ou les stemmates (steirnnata), yAacee entre le vertex et le vrai front, consiste 

 en un petite piece ordinairement demi-circulaife, ou les yeux lisses sunt im- 

 plantes. Le front, le vrai front (frous) s'etend d'un eeil a l'autre et de la region 



