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of the anus and behind the last sucker are four membranous 

 sacs provided with tracheae. The last were homologized (by 

 WlERZIEJSKl) with the four anal gills of Chironomus . 



The whcle body is leg-less but with six pairs of conical leg- 

 like appendages, on the sides of are scmetimes shcrt bristled 

 feeWs (genus Liponeura). 



The head bears except the two very little eyes a pair of 

 slender, long and joint-less or two jointed and short antennae. 

 Mostly important for systematical purposes is the form of the 

 chitin dorsal-plates, which lie in every segment and bears sharp 

 points, thorns or warts. The real locomotion organs of the 

 larvae are the six suckers. With them the larvae can hold so 

 fast to the rock that the body, when disturbed, is more readily 

 torn in two than dislodged as a whole. Thèse suckers are surelly 

 the best air-pump which we know in the whole animal King- 

 dom and their princip and mode of use are the same as in the 

 air-pump apparat constructed by man. 



The locomotion is alvays in latéral direction ; the moving larva 

 locsens the hold of three suckers at a time and swings to one 

 side the hinder half of the body thus released, the suckers again 

 attach this part of the body in its new position, and the other 

 half of the body is loosened and swùng over, and thus a slow 

 latéral translation of the larva takes places. 



The larvae like the lip of a fall, the rocks of cascades and the 

 sides of apot-hole in which the water is ever whirling and boi- 

 ling. They mùst hâve the highly aerated, swift water of the 

 stream's center and therefore cannot live in stagnant or even 

 quiet cr slow running water. They can live cnly in clear, 

 swifty running streams with a rapid fall, and this practically 

 limits thèse insects to mountain régions. Their whole organi- 

 saticn is also an excellent adaptation to such conditions. 



The larvae feed chiefly on Diatoms, although other food is 

 doubtless taken. 



* 

 * * 



H. — PUPJE. 



The pupa differs greatly in form from the larva 

 It is strongly convex on the dorsal side, where the skin is 

 hard and dark brown or black, and is perfectly flat on its ventral 



