70 



ZOOLOGY 



since respiration takes place at that end (Fig. 71, A, <?). 

 Upon emerging from the water, the mosquito floats in its 

 pupal skin until its legs and wings harden. Since a dis- 

 turbance in the water at this time would jeopardize the 

 life of the mosquito, this insect always breeds in quiet 

 waters. From the habits of the larvre, it follows that they 

 can be easily killed while in the pond by pouring kerosene 

 oil on the water, for this forms a film on the surface and 



FKJ. Tl. A crane-fly. Nat. size. Photo, by W. H. C. P. 



prevents respiration. The objection to this treatment, how- 

 ever, is that most of the other aquatic organisms also are 

 killed by it. 



The crane-flies (Tipulidse 1 ) look like mosquitoes, but can 

 easily be distinguished from them by the fact that they 

 have a V-shaped suture on the back of the thorax. 

 They are larger, and have relatively longer legs than the 



1 tipula, among the Latins an insect which courses rapidly on the 

 water, a water-spider. 



