HEAD ORGANS. 



231 



of insects, there are to be found portions developed to an 

 extent, and to which, from their analogy with the parts of 



Figs. 57, Head of Brentus-5S, 



Fulgora 59, Apodcrus #), Diopsis. 



the head of the higher animals, it may seem serviceable to 

 give analogous names ; but it is impossible to limit the ex- 

 tent of these parts, and therefore a general definition can 

 only be applied to each : as, that the forehead is that part of 

 the head which is between the eyes, and when the head 

 begins to assume a flattened form; and the cheeks those 

 parts which lie at the sides of the head between the eyes 

 and the mouth. In many insects the head is united to the 

 thorax by a membranous tube or neck, consisting (as in the 

 Diptera and Hymenoptera, in which the motions of the head 

 are very free) of the attenuated 

 fore part of the thorax. In some 

 beetles, however, the term neck 

 is applied to a narrowed portion 

 of the skull, which forms a kind 

 of rotule, playing in the opening 

 of the thorax. The three accom- 

 panying figures represent insects 

 with 1, the head of an ordinary 

 size (Attelabus curculionoides) ; 



2, the head posteriorly elongated (Apoderus avellana) ; and 



3, the head anteriorly produced (Rhynchites cavifrons), ali 

 being magnified about twice the natural length. 



