586 



INSECTA. 



which, however, they leave in some cases the last segment (pygidium), 

 or in other cases (StaphylinoR) several segments, exposed. As 

 a rule, when the insects are at rest, the straight internal edges of 

 both wing- covers are shut closely together, while the outer edges are 

 bent round the sides of the abdomen. Sometimes the inner edges of 

 the wings are fused together, so that the power of flight is 

 abolished. In rare cases the wings are altogether absent. The 

 head is seldom free, but as a rule is sunk into the freely moveable 

 prothorax, and bears very variously shaped, usually eleven-jointed, 

 antennae. In the male the latter are of considerable size and have 

 a considerable extent of surface. Ocelli 

 are with few exceptions absent, but the 

 facetted eyes are only absent in certain 

 blind species, which live in caves. The 

 mouth parts are adapted for masticating 

 and biting, and sometimes show transi- 

 tional forms to those of the Hymenoptera. 

 The maxillary palps are usually four- 

 jointed and the labial palps three-jointed. 

 In the predatory beetles, the external lobe 

 of the maxilla has a palp -like form and 

 articulation. The labium, which is sim- 

 plified by the reduction of its parts, is in 

 rare cases elongated to form a divided 

 tongue. The large prothorax (cervical 

 shield) is moveably articulated with the 

 mesothorax, which is usually w T eakly de- 

 veloped ; and on it, as well as on the 



FiG. 481. a. Cicindela, campestrit , 



b, c, its larva with the two dorsal other thoracic segments, the pleura ex- 

 hooks on the fifth abdominal tend on to the sternal surface. The 



segment (regne animal). . 



legs vary very much in shape, but usually 



end with a five-, rarely with a four-jointed tarsus. The tarsus is 

 rarely composed of a smaller number (from one to three) of joints. 

 The abdomen is attached to the metathorax by its broad base, and 

 always possesses a greater number of dorsal than of ventral plates, 

 of which some may fuse with one another. The smaller terminal 

 segments are usually retracted and concealed by the preceding. 



The nervous system of the Coleoptera varies in the greater or less 

 concentration of the ventral ganglionic cord. The subccsophageal 

 ganglion is followed by two or three thoracic ganglia, with the 

 posterior of which one or two abdominal ganglia may be fused. In 



