7 ~he Larva of Chironomus, Ephemera, and Dixa 



in their natural position and picking up stray bits of food of 

 all kinds. 



The larvae of other flies than mosquitoes are often met with in 

 water nnd may sometimes be mistaken for mosquito larvae. The 

 commonest are the larvae of the flies called Chironomus, EpJiemera 

 and Dixa. Chironomus larvae are often found in large numbers 

 when the mud at the bottom of a small pool is stirred up. They 

 are bright red worm -like creatures and are commonly known as 

 " blood worms." Although their tracheae open externally in a 

 pair of " respiratory tubes " ( fig. 2 D, d) in appearance they bear 

 no resemblance to mosquito larvae. The larvae of ephemeral flies 

 differ essentially from those of mosquitoes in that their air-tubes 

 do not open externally, so that they obtain the oxygen they re- 

 quire from the water by means of gills, the presence of which 

 makes them very easily recognisable (fig. 2 A & B. It should 

 also be noted that in Corethera larvae (fig. 2, C.) there is no direct 

 communication of the air-tubes with the external air. The larvae 

 of this kind of mosquito are very transparent, and are called for 

 that reason " Phantom larvae." The head is much smaller than 

 that of any other mosquito larvae. There are four distinct res- 

 piratory sacs which do not, however, contain air. The larvae have 

 no spiracles and, except when nearly full grown, no air-tubes. The 

 four air-sacs simply act as floats, and at no period of larval life is 

 there any direct communication with the external air. It will be 

 seen therefore that these larvae are very different from other mos- 

 quito larvse, and it is doubtful whether the ( *orethrince should be 

 classified with the true mosquitoes, 



Dixa larvae bear a superficial resemblance to " anopheles " 

 larvae and float just beneath the surface film as the latter do. The 

 fact that all the segments of Dixa larvae are almost equal in 

 size, the fact that they have no palmate hairs, and that they 

 possess four prolegs, by using which they creep up the side of 

 the vessel in which they are placed, should prevent any difficulty 

 being experienced in distinguishing these larvae from those of 

 " anopheles." 



THE PUPA OB NYMPH 



The pupae of mosquitoes are active creatures, rising and falling 

 in the water at will. Unlike the larvae, they can sink in the water 



12] 



