IXTRODUCTIOX. 



3 



External Structure. 



In shape and size these insects vary considerably, but the 

 general characters may be stated as follows : the head is rather 

 deeply sunk in the prothorax, the eyes are generally convex and 

 entire, the clypeus is subtrnncate, with the anterior margin 

 transversely depressed, and the antenna? are inserted on the 

 forehead behind the base of the mandibles ; the prothorax is 

 closely applied to the elytra, and is usually as broad or nearly 

 as broad as the latter are at their base. 



protnorax 

 1 st coxal cavity^ 



epimeron of 



the prothorax_. 



prosternum 

 me sos tern um 



2 nd coxal cavity . - 

 me taste mum 

 3 rd coxal cavity- 



abdominal 

 sternites 



head 



jTig. 2. — Ventral Tiew of Chrj/solina exanthemat'ica, Wied. The legs are 

 removed on one side. It should be noted that the prothoracic epimeron 

 does not meet the intercoxal process of the prosternum, this condition 

 being denoted by the phrase "anterior coxal cavities open behind." 



Head broad, generally of the same width as the emargination 

 of the front margin of the pronotum ; clypeus usually delimited 

 above by two inclined impressed lines (sometimes very deeply, 

 sometimes very feebly, impressed) meeting at an angle in the 

 middle ; eyes widely separated ; antenna) eleven-segmented, not 

 very long, never attaining the length of the body ; there is 

 always a difference between the five or six basal segments * and 



* Throughout this volume, in descriptions of the appendages, the term 

 "segment" is adopted in place of the term "joint" used in my previous 

 volume. 



