156 



HALF HOURS WITH INSECTS. 



[Packard. 



Fig. 124. 



the body. By dexterous strokes, aided h}^ a graceful but 

 rapid bending of tlie body, it seeks the surface and inspires 

 air through its thoracic respiratory tubes. In the same way 

 it descends to the bottom. 



The Corethra larva alters the specific gravity of its body 

 during the course of its wriggling, but as a pupa all this is 

 changed. It now resembles the mosquito pupa, has exter- 

 nal thoracic respiratory tubes and well developed tracheae ; 

 it loses its air bladders and swims by means of two terminal 

 paddles like those of the mosquito. 



We now come to the water beetles and bugs, whose move- 

 ments in the water are as graceful 

 as they are awkward on land. 

 Their whole organization, bodily 

 and p.sychical, as thoroughly 

 adapts them for tlie water as that 

 of the seal or whale for tlie same 

 element. They are the Amphibia 

 of the insect world. Born as 

 sailors, they take to the water on 

 being hatched and there remain 

 through their lives, only leaving 

 one pond to seek another, im- 

 pelled by a restless love of change, 

 which unconsciously to tliemselves results in good to their 

 race, preventing too close in-and-in breeding and the conse- 

 quent deterioration of the stock. Look at the body of the 

 Dj'tiscus (Fig. 125), so perfectly adapted for its aquatic 

 life. Remember that it is in reality a modified ground bee- 

 tle, such as Harpalus, the mouth-parts much the same, and 

 that the changes in form are mostly', if not whoU}^, such as 

 adapt it to its aquatic life. Tlie body is oval, both ends 

 alike, as in a boat, while the legs are perfect oars. The 

 hind legs, instead of being broad and spiny towards the 

 claws, as in the running ground beetles, taper to a point 



28 



Bfetisca. 



