l6o NATURAL HISTORY OF AQUATIC INSECTS CH. 



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that found in the larvae of Hydrobius and Pericoma. 



Valves and flaps and 

 outstanding processes, 

 all fringed with long 

 hairs, exclude the water 

 from a shallow sunk 

 space, upon which the 

 longitudinal tracheal 

 trunks open. 



The body is bent 

 from side to side, not 

 from above downwards. 

 Hence the whole of the 

 proper dorsal surface re- 

 mains dorsal. Six seg- 

 ments (5 — lo) are pro- 

 tected on the dorsal side 

 by as many shields, all 

 '! ^ I ^^!I^^ fringed by setae. -^ 



Reaumur's statement 

 that the two ends of the 

 body are in the water, 

 while the middle is out 

 of the water, is liable to 

 mislead. It would be 

 more correct to say that 

 the two ends are turned 



Fig. 47. — Larva of Dixa, in side-view and 

 from above. The species here figured 

 is not described in any of the systematic 

 books which I have consulted. The 

 fly is 6 mm. long, of yellow colour, and 

 with uniformly clear wings. 



1 These shields are not 

 found in all species of Di.xa. 

 They are absent in the larva 

 figured by Meinert, which 

 occurs also in England. 



