22 



IV. — Genits Psorophora. 



Our single species is of a yellowisli color, usually varied with brown, the bases oi 

 the tarsal joints white. It is considerably larger than any of our other species of 

 yellowish or brown mosquitoes: 



ciliatus Fabr. 



conterrens AValker. 

 molestvs Wied. 

 ? rubidus Desv. 



V. — Genus Megarhintts. 



Our three species are among the largest in this family, and are not known to occur 

 north of the District of Columbia. They may be separated as follows: 



All tarsi marked with white rutilus Coq. 



Hind tarsi alone marked with white purtorir.ens'ts Roeder. 



None of the tarsi marked with white hiemorrlioidalis Fabr. 



VI. — Genus Aedes. 



Our two species are among the smallest of our mosquitoes, an<l have a pale 

 brownish ground color. They may be distinguished as follows: 



Thorax marked with a median violet blue stripe fnipphirinufs O. S. 



Thorax destitute of such a stripe fuscus 0. S. 



THE BIOLOGY OF CULEX, WITH REMARKS UPON SOME OF THE SPECIES. 



It is tolerably certain that the life round of all of the species of the 

 genus Culex is practically the same. They will difier more or less in 

 the character of the water in which they preferal)ly breed, and differ- 

 ing in this respect, the}'^ will differ also in some degree in their pre- 

 ferred food, which consists of. all sorts of aquatic micro-organisms. 

 Down to the time when the writer putilished his account of Cvlex 

 pungens, in Bulletin No. -A, New Series, of this office, there was not 

 in an}^ published work a thoroughly satisfactory figure of a well- 

 determined species of mosquito from the United States, or of its 

 earlier stages. The statements quoted in the text-l)ooks and manuals 

 dated back in general to the time of Reaumur — more iiian one hun- 

 dred and fifty years ago. Reaumur's observations were made in the 

 month of May upon a species {( hdex jrijnens) which does not occur in 

 North America, and the observations were all made at Paris, so that 

 statements as to the duration of the insect in any stage would be 

 incorrect even for the same species in a warmer or colder locality. 

 The following account of the life history of Oulex pun gens (fig. 1) is 

 quoted from the writer's bulletin above cited: 



Life Jdsto7'y of Culex pungenx. — The operation of e.g^^ laying was 

 not observed, but it probably takes place in the very early morning 

 hours. The eggs are laid in the usual boat-shaped mass, just as those 

 of Culex pipiens, as described l)y Reaunuir. We say boat-shaped mass, 

 because that is the ordinary expression. As a matter of fact, however, 

 the ^gg masses are of all sorts of shapes. The most common one is 



