54 ORDER COLEOPTERA. 



IIYDRADEPHAGA. 



Tut insects Included in thi> Beetion reside in water, and hence their legs are transformed 

 into organs suitable for moving in this element. In addition to the transformation of the 



logs into swimmjng organs, the body undergoes a change of form, becoming oval or boat- 

 Bhaped : in fine they are thoroughly fitted for the element in which they an- to move, 

 being end iwed with the means of pursuing their prey, and furnished with all the con- 

 veniences which their congeners upon tin- land possess. Although thty subsist in water, 

 yet they are not provided in their perfect state for obtaining a supply of air from the 

 element in which they move : they are air-consuniers, and are obliged to rise occasionally 

 to the surface to obtain a supply of air for respiration. 



The Hydradephaga are predacious beetles; and although it is not important to the 

 farmer to know them in an economical point of view, -till some of the larger kinds prey 

 upon the ova of fish, and even upon their young; and in this respect, they are not entirely 

 destitute ^'t' interest to the owners of fish-ponds. Regarded as animals which live by the 

 chase, they are truly more greedy and gluttonous than the predacious land beetles : they 

 are pre-eminently voracious and destructive. Their larvse, of course, are aquatic; and 

 they too feed voraciously upon other acpuatic insects. The perfect animal, though fitted for 

 the water, is not confined to it : it may take wing at evening, and enter dwellings, like 

 moth-, being allured by the dazzling light of lamps near a window. They obtain air by 

 resting upon the surface, and raising their elytra : this brings the air more immediately 

 into contact with the spiracles of the insect. 



Stephens divides the Hydradepiuga into two families, viz : 



. ( long, setaceous : embracing the Dyticidje ; 



( short, clavate : embracing the Gyrimdje. 



1. The Dyticidj; are furnished with rather long setaceous antenna? ; their bodies are 

 oval, being rounded anteriorly and posteriorly ; their thorax is short and transverse, and 

 their leg- are formed for swimming : the posterior ones, however, are especially adapted 

 to this end, by their great length, and by being furnished with two rows of dense cilia 

 arranged along the edges, with the view of increasing the width of the oar ; the tarsi are 

 also flat in the males, and the anterior ones are more dilated than in the females. The 

 mandibles of the larva are much bent, and are pierced for the purpose of extracting the 

 juices from the animals upon which they subsist. Their respiratory organs are situated 

 behind, and consist of two segments fringed with hairs and terminating in two conical 

 appendages, between which are two cylindric perforated tubes : these communicate with 

 the respiratory organs. The larva, as well as the imago, is obliged to rise to the surface to 

 obtain a supply of air. 



