DIPTERA 



805 



tube at the surface. (Fig. 102 1). At the end of this tube there is a 

 rosette of plate-like lobes (Fig. 1022, a) which resting on the surface 



Yerttral brush 

 of ^fh seamen, 



Fig. 1020. — Larva of Culex showing 

 details of external structure. (From 

 Riley and Johannsen.) 



Fig. 1 02 1. — A glass of water containing eggs, 

 larvae, and pupae of mosquitoes. 



film, keeps the larva in position. At the end of the last abdominal 

 segment there are one or two pairs of tracheal gills. About the mouth, 

 on the antennse, and on the caudal segments of the abdomen are 

 tufts of setae that afford characters much used in the classification of 

 mosquito larvae. These various tufts have received 

 special names as indicated in Figure 1020. 



The food of mosquito larvae varies with the 

 different species, with most of them it consists of 

 organic matter in suspension in the water, or 

 floating upon the surface, or settled or growing 

 upon the bottom. Some mosquito larvae are can- 

 nibalistic; those of the Corethinae are all preda- 

 cious and seize their prey with the antennEe. 



So far as is known, there are four larval instars 

 in all species of mosquitoes, with the fourth molt 

 the larva becomes a pupa. 



The pupae of mosquitoes like the larvae are aquatic, but they differ 

 greatly in form from the larvae. (Fig. 1023). The head and thorax 



Fig. 1022. — c, end of 

 breathing tube of 

 larva; 6, breathing 

 tube of pupa. 



