8 OUTLINES OF ENTOMOLOGY. 



separately. On the thorax of mauj smooth, hard-shelled insects, like 

 wasps and beetles, we can readily trace the divisions of each joint by 

 means of fine impressed lines. 



The insect crast varies greatly in texture and thickness. In some 

 Insects, and especially in many larvse, it is very thin, easily bent and 

 easily broken; in others it is hard and brittle like shell, or dense and 

 impenetrable like metal. Examples of the shelly texture are found in 

 the pupse — termed chrysalides — of butterflies and moths, while the 

 metal-like covering may be seen in the cases of the beautiful Brazilian 

 beetles, often used by jewelers in the place of gems, which are so 

 hard that they can only be pierced by a drill. 



The majority of insects have the head separated from the thorax 

 ;and the thorax from the abdomen by deep incisions, or the contraction 

 of the connecting joints. This will be understood by a glance at the 

 illustration at the head of this chapter, or better still by examining the 

 body of a bee, a butterfly or a fly. 



The back or upper surface of the body of an insect is termed the 

 dorsum or dorsal surface, or tergum, the sides the pleurites or lateral 

 surfaces, while the under side is the venter or ventral surface. The top 

 of the thorax is sometimes further distinguished as the notum, the 

 under side, or breast, being correspondingly termed the sternum. 



In exact scientific description a number of other terms are used 

 to indicate the various divisions of a segment, or to refer to precise 

 localities on the body, but these are not necessary to a general appre- 

 hension of the structure, and would only confuse and discourage a 

 beginner. 



CHAPTER III. 



THE HEAD AND ITS APPENDAGES. 



As with the higher animals, the head of an insect 

 is more especially the sensorial region, because it 

 contains the organs of sight, touch, taste, smell, and 

 possibly in some species, of hearing also. The sense 

 of feeling is not, of course, confined to the append- 

 ages used by the insect for touching objects — which 

 in this sense correspond to the human hand — but ex- 

 tends over the entire surface of the body. ci?uT'^6°ep]Iraninra°c" 



Certain localities on the head are frequently re- ^aws''''''^'^''"''"^'"^"'^ 

 ferred to in descriptions of insects. The more important of these are : 



