THE HARLEQUIN-FLY 117 



without education or example, at once execute so difficult a 

 manoeuvre as that of flight, for it flies as swiftly, and steers 

 its course as certainly, as the most practised insect. 



The fly of Chironomus is a delicate insect with long legs 

 and gauzy wings. It may easily be recognised as Dipterous, 

 by its single pair of functional wings, and by the rudimentary 

 hind-wings or halteres, which project from the third thoracic 

 segment. On the head may be seen the great compound eyes, 

 nearly meeting above in 

 the male, but somewhat ', 



smaller in the female. The >'>- 



antennae spring from the 

 face. In the male they 

 are plumose, and of re- 

 latively large size; in the 

 female they are smaller 

 and of simpler structure. 

 The second joint, especi- 

 ally in the male fly, is 

 enlarged, and forms a 

 spherical chamber, which 

 is believed to lodge the 

 organ of hearing. The 

 antennge of the male fly 

 are thirteen -jointed; the 

 simpler and smaller an- 

 tennas of the female are 

 eight-jointed. The antenna 

 of numerous joints char- 

 acterises a primary divi- 

 sion of Diptera known as 

 Nemocera. The rest of 

 the Diptera have, like the blow-fly, antennae of the plate and 

 bristle type, with three rather large joints and a bristle project- 

 ing on one side (see p. 209). From the rostrum, which forms the 

 lower part of the head, project the mouth-parts, of which the 

 long, four-jointed maxillary palps are the most conspicuous. 

 The digestive apparatus is taken over from the larva and pupa 

 to the body of the fly. During the pupal stage it shrinks 

 and collapses, and is never used again. The fly does not feed 

 at all, and there is not even a passage from its mouth to its 



_ Fig. 65. — Head of male Chironomus fly, in 

 side-view, showing antennse, compound eye, 

 and mouth-pans. 



