COI,K()I'TERA OF INDIANA. 



a.,//,,: 



THE EXTEltXAL ANATOMY OF A BEETLE. 



Having- thus seen that a beetle l)eh)nij;s to the class Insccfa, it is 

 thought best, before giving- its relation to the other orders of that 

 class, to descril)e brieHy the external parts of a typical specimen. 

 The beginner may thus the more 

 readily grasp the name and loca- 

 tion of the parts used in classifica- 

 tion, as well as the meaning of 

 many of the technical terms which, 

 of necessity, have to be used in such 

 a i)aper. The three regions of the 

 body, the head, the thorax and the 

 abdomen, will therefore be consid- 

 ered in order. 

 The Head and Its Appendages. 

 The front part of the body, the 

 head, is composed of three or more 

 rings or segments, completelj" fused 

 or compacted into a single hard box 

 or cavity called the epicramum. 

 Tliis contains the brain and acces- 

 sory ganglia, the mouth cavity and 

 the muscles moving the mandibles, 

 antennae and otlier sense organs 

 borne on the outer surface. 



The heads of beetles vary great- 

 ly in shape and size, and are joined 

 by a membrane to the thorax. Usu- 

 ally the portion behind the eyes is 

 more or less constricted into a neck, 

 M'hich may be very long and nar- 

 row, or short and partly or wholly 

 immersed in the thorax. The up- 

 per part of the head is divided into 

 three regions, th(^ liack part being 

 called the occiimf, the middle part 

 behind the eyes the vrrfcr, while 



the frontal portion, as fjir down as a more or less prominent trans- 

 verse suture betwe-n or in front of the antenna\ is called the front. 

 Tliis suture is known as tlie rliipfitl or frontal suture, and its pres- 

 ence or alisence, position, depth, etc., is often used in classification. 



Fig. 1. Under surface and head from 

 above of beetle {Harpalus caliginosus) show- 

 ing the different parts. (After Smith.) 



