HOW TO KNOW THE IMMATURE INSECTS 



12a. Apical abdominal segment terminating in 2 or 4 paddle-like or 

 iin-shaped organs which are fringed on all or part of outer sur- 

 face by strap-like hairs; or ii the apical segment terminates in 

 2 long subcorneal processes, the tarsi are recurved against the 

 ventral surface of the base of the abdomen and apex of thorax 

 so that they do not extend beyond apices of wings 13 



12b. Apical abdominal segment obtuse, armed with short or elongate 

 spines or thorns; or if ending in a pair of long, slender processes 

 they are more or less oval in cross section and without strap-like 

 hairs; tarsi generally entirely straight, rarely the apices of the 

 hind pair incurved slightly, but never recurved as above 18 



13a. Thoracic respiratory organs terminating in numerous thread-like 

 filaments Family CHIRONOMIDAE 



13b. Thoracic respiratory organs consisting of a single stem, in some 

 cases with a few long, or many short, scale-like, surface hairs, 

 but never terminating in numerous thread-like filaments; occasion- 

 ally the thoracic respiratory organs not elevated 14 



14a. Thoracic respiratory organs not elevated; stemopleura exposed. 

 Family CHIRONOMIDAE 



14b. Thoracic respiratory organs conspicuously elevated 15 



15a. Thoracic respiratory organs situated close to anterior margin of 

 thorax; no stellate hairs on thorax and abdomen. 

 Family CHIRONOMIDAE 



15b. Thoracic respiratory organs situated close to middle of thoracic 

 dorsum 16 



16a. Apical abdominal segment ending in 2 or 4 broad, flat, paddle- 

 like plates. Fig. 566 Family CULICIDAE 



The pupae are very active and float at water 

 surface to breath air by a pair of trumpet-like 

 respiratory organs on the thorax. This permits 

 their destruction by oil or poisons placed on 

 the surface of the water. 



Fig. 566. Culex sp. 



204 



