The head exhibits no distinct divisions, but bears the 

 following appendages : the eyes, antennae, and organs of 

 the mouth, or trophi. 



The eyes are of two kinds, compound and simple. The 

 former (Fig. I. c c) are situated on the sides of the head 

 above the mouth, and consist of two large hemispheres^ 

 composed of a great number of hexagonal divisions, each 

 of which is a complete eye in itself. The latter (s s) are 

 usually three in number, and are situated on the top of the 

 head between the compound ones. They are, however, 

 frequently wanting. 



The antennae (a) are two jointed organs, one of which is 

 placed on each side of the head, between the eyes ; their 

 functions are at present extremely doubtful, but they are 

 invariably found in all insects. 



The organs of the mouth consist of the following : the 

 labrum (Fig. II. 3), or upper lip, a horny plate, closing 

 the mouth from above; the mandibles (i i), or upper 

 jaws, two strong bent hooks, articulated to the head on each 

 side of the mouth, and opposed to one another like scissor 

 blades ; the maxillae (2 2), or under jaws, resembling the 

 mandibles, but more delicately constructed, and furnished 

 with a pair of jointed appendages termed maxillary palpi 

 (5 5) ; and the labium (4), or lower lip, consisting of a 

 horny plate somewhat resembling the labrum, but provided 

 with two jointed appendages termed the labial palpi (6 6). 

 All these organs are subject to great modification in suc- 

 torial insects, which I shall notice further on, when dealing 

 with the differences between the various orders. 



The thorax consists of three primary divisions, viz., the 

 prothorax (Fig. I. b), mesothorax (d), and metathorax 

 (k). The upper surfaces of these are termed the pronotum, 

 mesonotum, and metanotum respectively, and the under the 

 prosternum,mesosternum,and metasternum ; other divisions 

 exist in some insects, but they are not of a sufficiently 



