356 ZOOLOGY 



oral appendages are at the end of a long snout. The mouth 

 appendages are of the type described in Melolontha ; as a rule 

 the maxilliary palp is four-jointed, the labial palp three- 

 jointed. 



The prothorax is well developed, the mesothorax small, 

 and the metathorax of fair size. The legs are usually adapted 

 for running, but in some cases they are flattened for swimming 

 or strengthened for digging. The number of joints in the 

 tarsus is usually four or five, but it may be smaller, and this 

 variation forms the basis for grouping the various families into 

 sub-orders. 



The anterior wings or elytra, when at rest, meet in a 

 straight line which terminates anteriorly at a small triangular 

 area of the mesothorax termed the scutellum, often invisible 

 except when the wings are opened or the prothorax extended. 

 In some families, as the Staphylinidae, the wings only extend 

 over the anterior abdominal segments, leaving the larger part 

 of the abdomen exposed. In rare cases they and the hind 

 wings are absent, as in the female Lampyris. 



The elytra are in some species fused together, and the 

 posterior wings are then feebly if at all developed ; flight is 

 therefore impossible. In the more normal forms the beetle, 

 when flying, extends the elytra at right angles to the body, and 

 keeps them in this position motionless (Fig. 204). 



The ventral surface of the abdomen is more strongly pro- 

 tected by chitin than the dorsal, which is covered in by the 

 thick elytra. The hinder segments are often invaginated, and 

 form a recess connected with the openings of the generative 

 organs. 



One or two genera of the Elateridae, and almost all the 

 Lampyeidae, are provided with phosphorescent organs, usually 

 in both sexes. In the males of the latter order, the light- 

 giving structures shine through the ventral surface of the two 

 posterior abdominal segments ; in the former they are placed 

 in the prothorax, and on the suture between the thorax and 

 abdomen; in both cases they consist of numerous fatty cells, 

 with a very rich supply of tracheae and nerves. 



Beetles usually lay their eggs in the neighbourhood of the 

 food which will afford support to their larvae. The latter are 



