﻿EXTERNAL ANATOMY OF THE COLEOPTERA. 



23 



There are also in some few beetles two ocelli, or addi- 

 tional eyes, small, and not composed of facets, on the 

 back of the head ; these are especially noticeable in 

 Omalium, a genus of the Brachelytra. The antennae 

 are long flexible instruments, through which the insect 

 certainly receives a considerable amount of sensation, 

 either by actual contact or atmospheric influence. They 

 are nearly always composed of eleven joints, though 

 some of them are often indistinct, being clubbed to- 

 gether, and in a few species the absolute number varies ; 

 for instance, in the male of Ischnomera melanura there 

 are twelve joints, though the normal number is found 

 in the female. They are inserted into a cup-like socket 

 in the head, and have often the first or basal joint long, 

 and the second short ; but their variations in structure 

 are too numerous to be specified here. 

 Fiff. 4 shows the 



under 

 head ; 



side of the 

 a, b, and c 



forming the labium 



or lower lip, where- 

 of a is the menium 



or chin, b the ligula 



or tongue, and c c 



the labial palpi or 



lip feelers ; d d are 



the maxilla or lower 



jaws (which are 

 dissected out, and 

 show the upper and 

 under sides), com- 

 posed of the following pieces : — d^, the inner or palpiform 

 lobe; d^, the maxillary palpus or jaw feeler; d^, the 



Fig. 4. 



TJiider side of head of D. marginalis, {JiigJily 

 ■magnified). 



