24 



BRITISH BEETLES. 



lacinia or blade ; d 4 , the palpifer ; d 5 , the stipes or stalk, 

 and d 6 , the cardo, base, hinge, or insertion, by which 

 the lower jaw is attached to the inner side of the head. 



There are two small organs, 

 the paraglossce, which in 

 Dytiscus are soldered to the 

 sides of the ligula : these are 

 very conspicuous in many 

 Coleoptera, and will be seen 

 in Fig. 5 (the labium, or lower 

 lip, of Pterostichus niger, a 

 very common black ground- 

 Fig- 5 - beetle), in which a is the 



Labium of Pterostichus niger. , -, /_ ,1 7-7 



mentum, and b the ligula ; 



c c are the paraglossse, and d the labial palpi. 



The next segment is the thorax, which is divided into 



three parts, the prothorax, mesothorax, and metathorax. 



The first of these, the prothorax, is considered to consist 



of two portions, the upper side, called pronotum, and 



the under side, or prosternum. The pronotum is that 

 part to which the word thorax 

 is exclusively applied in descrip- 

 tions, and is much developed in 

 the Coleoptera. In Fig. 6, a is 

 the anterior, b the posterior, 

 and c the lateral margin ; d, the 

 medial line (of which the front 

 extremity is called the apex, 

 and the hinder the base] ; e e 



are the anterior, and / / the posterior angles, and g 



the disc. 



Both this and the following upper thoracic segment 



are considered each to be normally composed of four 



Fig. 6. 



Pronotum of thorax of 

 JD. marginalia. 



