54 ORDER COLEOPTERA. 



HYDRADEPHAGA. 



The insects Includwi in this section reside in water, and hence their legs are transformed 

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

 legs into swimming organs, the body undergoes a change of form, becoming oval or boat- 

 •haped : in fine they are thoroughly fitted for the element in which they are to move, 

 being endowed with the means of pursuing their prey, <and furnished with all the con- 

 veniences which their congeners upon the land possess. Although they 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-consumers, and are obliged to rise occasionally 

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



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

 farmer to know them in an economical point of view, still 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 of 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 larvae, of course, are aquatic ; and 

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

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

 moths, 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 Hvdeadephaga into two families, viz : 



Anttnn* J ^o"8' setaceous : embracing the DYTiciDiE ; 

 ( short, clavate : embracing the Gyrinid.s;. 



1. The DyxiciDiE are furnished with rather long setaceous antennae ; their bodies are 

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

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

 to this end, I)y 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, Ijetween 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. 



