THE HEAD. 63 



eyes. In some of the Coleoptera, a corneous process originating at the 

 clypeus (canthus of Kirby and Spence), either completely or partially 

 divides the eyes, and these beetles, (Ateuchus, Geotrupes, Fabricius, &c. 

 &c.) then appear to have four eyes. The genus Tetraopes, also, among 

 the Capricorn beetles (Cerambycina), has apparently four eyes, from 

 the antennae being inserted exactly in the middle of the long ovate eyes, 

 and which thence seem divided into an upper and lower half. 



The SIMPLE EYES or auxiliary eyes (ocelli, oculi simplices, PI. VI, 

 f. 8, B, stemmata, Kirby and Spence), are generally THREE in number, 

 and more rarely we find but TWO. They are placed upon the vertex or 

 upon the brow, most frequently in a triangular position ; they are 

 much smaller than the true eyes, and consist of but one very convex 

 case. They are found in all the orders of insects ; among the Cole- 

 optera, indeed, only as exceptions *, in others, the Diptera, for 

 example, very universally. The larvae of insects with a perfect meta- 

 morphosis are destitute of compound eyes, and instead of them have 

 mostly simple eyes ; in many instances they have none. 



THE ANTENNAE (Antennae). 



72- 



The ANTENNJE must be distinguished as the third most important 

 group of the organs of the head. They are two jointed organs, one 

 of which is placed upon each side of the head between the angle of the 

 mouth and the eyes. They appear never to be wanting, and there are 

 never more than a single pair present. In some parasites only (Plulop- 

 terus, Docophorus), there is close to and in front of each of them a small 

 moveable stalk, which Nitzsch has called the little BEAM (trabeculus). 

 It is different in the classes nearest to that of insects, the Crustacea, 

 Myriapoda, and Arachneodea ; in which we find sometimes none, 

 sometimes only two, and even four, or six antennae. 



As the differences of antennae are very great, we must divide our 

 consideration of them under several heads. These are their situation, 

 relation to the body, their general construction, construction of the 

 individual joints, and their clothing. 



* Germar discovered them in Omalium ; they were afterwards discovered in Antho- 

 phagus and Paussus. A very particular observer, on the contrary, Straus-Dtirckheim, 

 denies their being eyes, although he does not dispute the existence of the points, page 58. 



