THE HARLEQUIN-FLY m 



much wool as to hide the larva. A low power will be best for 

 examination. 



The body consists of a very small head, and twelve segments. 

 On the head will be found a pair of short feelers, two pairs of 

 eye-spots, which are mere blotches of pigment without lenses, 

 a labrum, and a pair of stout, toothed mandibles. The maxilte 

 are reduced to minute vestiges. The labium is represented 

 by a flat ' plate, with toothed margin, which lies behind the 

 mouth and aids the action of the mandibles. On the first 

 thoracic segment is a pair of feet, armed with numerous hooks, 

 which are used for locomotion within the burrow. A pair of 

 rather similar, but less mobile appendages (the anal feet) 

 project from the last segment. These, like the anal feet of 

 a caddis-worm, are often used for holding on to the burrow. 

 On the last segment but one, four slender and hollow tubules 



Fig 62. — Larva of Chironomus dorsalis. X 3. 



will be seen to stand out from the ventral surface. Four short, 

 hollow outgrowths can also be seen on the last segment, close 

 to the outlet of the intestine (see fig. 62). On the dorsal 

 surface of the last segment a pair of small brushes will be 

 found, which are probably sensory. The heart can readily be 

 seen pulsating beneath the transparent skin. It lies on the 

 dorsal surface near the tail-end, and gives off a long dorsal 

 vessel, which passes along the back to the head. Two pairs 

 of lateral inlets admit the blood to the heart from the body- 

 cavity. The ahmentary canal is traced without difficulty. A 

 long and narrow gullet proceeds backwards from the head. 

 In the metathorax it suddenly expands into an enlarged and 

 muscular cardiac chamber. This has a very uneveii appear- 

 ance; a number of prominences stand out from its outer 

 surface, which look like tubular outgrowths. They are, how- 

 ever, solid and not hollow. Beyond the cardiac chamber comes 

 the stomach, which is unusually long, and narrows irregularly 

 behind. Four long and winding Malpighian tubules mark 

 the beginning of the intestine, which is at first narrow, but 



