CHAP. XVII 



INSECT A: COLEOPTERA 



243 



a complete and great metamorphosis. The larva is some- 

 times a legless grub, but often there are three pairs of small 

 thoracic legs j the pupa is soft, with no hard protective 

 pupal case ; the organs of the imago show clearly through 

 the thin pupal skin. This order is an enormous one 

 numerically. It is reckoned that about 150,000 species are 

 already known, and this number is constantly being added to ; 

 a little over one-fiftieth of these are British. 



On the whole, beetles are not such good fliers as most insects ; 

 indeed many of them use their wings but rarely, living mostly 

 close to the ground where vegetation is dense and food plenti- 

 ful. In some of these ground beetles the membranous wings 

 are mere rudiments. A good many British forms are aquatic, 

 and since the life-history of these is usually more easy to follow 

 than that of the land forms, one of them will now be taken 

 as the type for detailed study. 



Sub-order 1 : Adephaga (Beetles with Thread-like Antennae). 



These forms are sometimes also known as the " Carnivora," 

 on account of the nature of 

 their food. The larvae as well 

 as the adult beetles are excep- 

 tionally active and predaceous. 



Type, : The Carnivorous Water 

 Beetle (Dyticus marginalis). 



Dyticus marginalis is a large 

 handsome beetle, very common 

 in ponds, often seen at the sur- 

 face as it tilts the tip of its 

 abdomen out of the water to 

 take in a fresh supply of air. 

 If alarmed, it dives very rapidly 

 down to the bottom, soon, 

 however, floating up again, for 

 its body is lighter than the 

 water, and so it is unable to 

 remain below except by active movement or by clinging to 

 some support. This beetle can be very easily kept in 



FIG. 169. The Carnivorous Water 



Beetle ( Dyticus marginalis). 



a, Antennae ; d, disc on front leg, 



characteristic of the male. 



