64 



INTRODUCTION. 



general facies of the insects is a very important character in the 

 group, and this can only be learnt by actual experience. We 

 agree with Dr. Sharp in believing that, although the DYTisciDiE 



exist in water as larvae and 

 perfect insects, yet there are 

 reasons for supposing that they 

 are terrestrial insects which have 

 become modified for a more or 

 less aquatic life. The reasons 

 are, firstly, that in general 

 organization they are similar to 

 the Cakabidje and are more 

 easily drowned than many land- 

 beetles, much more easily, for 

 instance, than several of the 

 subaquatic Eiiynchophora be- 

 fore referred to ; secondly, that 

 they are capable of existing on 

 land, and of taking prolonged 

 flights in the air (on hot days 

 they are often found on or close 

 to the glass of garden frames, 

 etc. which they have mistaken 

 for water, thus proving that 

 they are guided by sight and not 

 by smell or any other sense) ; 

 thirdly, that the pupa is always 

 terrestrial ; the pupae of Hy- 

 phydrus for instance, may be 

 found in numbers in summer in 

 the drying or dry mud of the 

 sides of pools, well above high- 

 Fig. 28. - Hydroporus parallelo- water mark 5 and fourthly, that 

 grammus. Larva x 10. (After like the Cetacea, they cannot live 

 Schiodto. without coming to the surface 



for air, which is taken in under 

 the elytra by the insect exposing the hind tip of its body just 

 above the surface. 



In Dytlscus the females are often deeply grooved on the back, 

 thus affording the male a better hold, although it hardly requires 

 it, as the front foot is dilated into a remarkable palette, covered 

 with suckers of various sizes (fig. 27) ; dimorphic forms of the 

 female resembling the male also occur. In many of the smaller 

 species (Hydroporus, etc.), the males are bright and shining and 

 the females dull, the sculpture being rougher. 



The larvae of the DYTisciDiE are long insects with large, more 

 or less sickle-shaped jaws, which are not toothed, but are furnished 

 with a lobe near the tip and another at the base and a canal 

 passing through their length, through which they suck their prey 

 after piercing it with the sharp tips. They vary in the shape of 



