CULEX PIPIENS 367 



The species breeds continuously in warm weather and in consequence increases 

 in numbers as the season advances. Knab, in Massachusetts, found that the 

 larvae began to appear in May. Eggs, larvae and pupae are destroyed by the first 

 frosts. The larvae most frequently occur in artificial receptacles, but also in 

 ground pools when these are sufficiently polluted. In cities they breed exten- 

 sively in the catch-basins of sewers. Here, when there is a long period without 

 rain and the sewers are not flushed, they increase enormously. Six days is given 

 as the minimum larval period, but frequently it is much longer and it may be 

 greatly prolonged by unfavorable food and temperature conditions. The pres- 

 ence of organic matter favors the development of this species and it is able to 

 thrive in highly polluted water. In a case observed by Knab, and already quoted 

 under the mating habits, the water was highly charged with the refuse from 

 slaughtered animals; here the larvae were so numerous that the ends of their 

 breathing-tubes at the water-surface gave the appearance of a scum ; egg- rafts 

 were present over an extensive surface to the number of about 20 to the square 

 foot. Larvas, pupas and eggs were still present early in November. Ficalbi, for 

 Italy, states that the larvae sometimes occur in swamps as well as in ditches, but 

 that they occur most frequently in artificial receptacles in and out of doors. He 

 has found them in the fonts of consecrated water in churches. He has also 

 found them in sulphurous water. At Murphysboro, Illinois, Mr. C. A. Mosier 

 found the larvae in a large hall, in December ; they were in basins vidth water into 

 which tubs with palms were set. 



Temperate regions of the northern hemisphere, but not in the extreme north ; 

 in North America, the northern Atlantic coast region, westward through Illi- 

 nois ; Europe and probably temperate Asia. 



Virginia Beach, Virginia, September 20, 1911 (H. G. Byar) ; Arlington, 

 Virginia (T. Pergande) ; Washington, District of Columbia, October 20 (H. 

 G. Dyar) ; Williamsport, Port Jervis, Johnstown, Pittsburg, Springdale, Norris- 

 town, Pottsville, Devon, Altoona, York, Harrisburg, Ardmore, and Sunbury, 

 Pennsylvania (H. L. Viereck) ; Bellport, New York (H. G. Dyar) ; Ithaca, New 

 York (0. A. Johannsen) ; Fairfield, Connecticut, August and September, 1910 

 (V. Havard) ; West Springfield, Massachusetts (F. Knab) ; Durham, New 

 Hampshire (H. G. Dyar) ; Chicago, Illinois (E. 0. G. Kelley) ; Murphysboro, 

 Illinois (C. A. Mosier) ; Urbana, Illinois (F. Knab) ; Copenhagen, Denmark 

 (F. Meinert) ; St. Eemy la Varenne, Maine et Loire, France (R. du Buysson) ; 

 Buda-Pesth, Hungary (C. Kertesz) ; Malaga, Spain, December, 1908 (C. 

 Visich). Also reported from the Azores, Japan and generally distributed 

 through temperate and southern Europe and northern Africa; also south 

 eastern Africa. Probably also widely distributed through temperate Asia. 



We consider Culex pipiens to be a species introduced into North America 

 from Europe. Its comparatively restricted distribution in this country indicates 

 this. We have convinced ourselves that our species is identical with the Euro- 

 pean by study of male genitalia of European and North American specimens. 



Meigen appears to have been the first to restrict the name to the common 

 house-mosquito of central Europe. On the other hand Zetterstedt (Insecta 

 lapponica, 807, 1840) applied the name to forms which we now refer to the 

 genus Aedes. This necessitates the elimination of a number of the references 

 under Culex pipiens. As a result of the division of opinion in the restriction of 

 Culex pipiens, Ficalbi proposed the name Culex licematopliagus for the present 

 species (Bull. Soc. ent. Ital, xxv, 143, 1893). A considerable synonymy obtains 

 in the European literature, but on examination we have almost completely dis- 

 carded it. Blanchard includes in the synonymy Culex ciUaris Linnsus, Culex 



