184 MOSQUITOES OF NORTH AMERICA 



the species of Aedes and Anopheles. In those forms in which the abdomen is 

 compressed or wedge-shaped, it is often very difficult to get the parts into posi- 

 tion for a dorsal view. It is then necessary to press the tip of the abdomen with 

 forceps until the parts lie flat, and this is best done while the specimen is in the 

 oil of cloves. Sometimes the end pieces of the claspers are folded under, and 

 then it requires careful manipulation to bring them into view without injury. 

 In certain cases, where the genitalia are very compact, and in others where they 

 are very complicated, it becomes necessary to break them up in order that the 

 details may be brought into view. This must be done carefully under a dis- 

 secting microscope or a good lens, and requires skill and practice. 



The slides should be numbered and the data entered in a book. The mosquito 

 from which the genitalia were taken should receive a pin-label referring to the 

 number which has been given to the slide. 



Whole adults or portions of them or entire larvae which it is wished to mount 

 can be treated with caustic potash in the manner above described. 



COLLECTING LARV/E. 



All mosquito larvge are aquatic, and all sorts of water should be examined to 

 collect them. In general, lakes, ponds and streams are not suitable breeding- 

 places, for these larger bodies of water contain insufficient nourishment for 

 the larvae, and generally do contain fish, which would devour any larvae that hap- 

 pened to appear. It is exceptional for mosquito larvae to be found in large, or 

 running bodies of water, though there are such exceptions. Anopheles larvie not 

 infrequently breed along the margins of swiftly running streams, and large 

 ponds may harbor Culex larvae in their grassy edges. Mansonia larvae live in the 

 mud at the bottoms of the sedgy swamps, attached by their air-tubes to the vas- 

 cular roots of the aquatic vegetation. In the tropics, almost any water may con- 

 tain larvae. The collector will, however, iind the best results in small stagnant 

 collections of water, particularly those of a transient character. The different 

 genera will be found to occur in different situations. For example, Aedes, with 

 the Psorophora that prey upon them, in temporary ground pools, some species in 

 tree-holes ; Culea-, with the predaceous Lutzia, in permanent or semipermanent 

 ground pools ; a few species in tree-holes ; Bancroftia, with their enemy Mega- 

 rhinus, in tree-holes, some species in bromeliaceoue plants ; Deinocerites and 

 allies in crab-holes ; all the sabethids in water in tlie leaves or flower-sheaths of 

 plants, some species in tree-holes, etc. The sabethid larvae, in the tropics, re- 

 quire especially careful search, as they occur in such peculiar locations, while 

 every different plant harboring them will be found to have its own fauna both 

 of Wyeomyia, etc., and the predaceous Lesticocampa and others. This fauna is 

 especially characteristic of the tropics, where many plants are water-bearing ; 

 but in our temperate region only a single sabethid occurs. It has, however, the 

 nonnal habits of its tribe, living in the water in the leaves of the pitcher-plant, 

 Sarracenia purpurea, the only water-bearing plant of temperate distribution. 



The season of the year is an important factor in the occurrence of species, 

 rains being essential to the development of perhaps the majority of larvte. Espe- 



