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from the plants, and it is possible that this air too, caught and drawn in by the 

 sipho, is used by the larvae. I have never directly observed this phenomenon, but 

 the supposition is rather obvious, because these air-bubbles play a prominent part 

 in the respiration of many other insects in winter, more especially Dytiscids. 



Geographical distribution: It is very difficult to clear up the range, of 

 C. morsitans. LANG (1920 p. 103) designates it as a mainly British species, which is 

 further found in Ghent, France, Holland and Macedonia. 



Genus VII. Culex. 



1. C. pipiens Linne. 

 Tab. XX. 



Imago. This species may be regarded as our only, true house mosquito 

 the temperate zone of the old world. It is introduced into North America in 

 from Europe and according to HOWARD, DYAR and KNAB (p. 366), has there con- 

 quered the northern cities, breeding in various receptacles containing water. In 

 America it is usually rare or absent in the rural districts, being largely replaced 

 by C. restuans. 



Taken in the widest sense the species is easily recognizable from all other 

 Danish species and most probably from all species of Northern Europe, by its ex- 

 tremely long and narrow second marginal cell, the fork of which is at least seven times 

 as long as the stem and much longer than the second posterior cell. Also the brick- 

 red or reddish-brown colour of the mesonotum, unique in our mosquito fauna, 

 makes it easily recognizable. In the domesticated and most common form the 

 mesonotum has generally three lines of black bristles, but especially in older speci- 

 mens they are inconspicuous or obsolete. Also the flaxen-yellow bands of the ab- 

 dominal segments dorsally and the same colour of the venter helps to distinguish 

 this species from the whole of the other mosquito fauna. 



Formerly we have here in Europe described very many species, which now 

 are all referred to this very same species C. pipiens Linne (C. uulgaris Linne, C. alpinus 

 Linne, C. agilis Bigot, C. ciliaris Linne, C. communis de Geer, C. rufus Meigen, C. 

 phytophagus Ficalbi, C. domesticus German). As most of these species, owing to the 

 descriptions, are irrecognizable, this method was most probably the most correct. On 

 the other hand I feel quite sure that C. pipiens, as we now regard it, is really a collec- 

 tive species, which further explorations will dissolve into several smaller ones. This 

 more especially holds good if we also take the larvae into consideration, which 

 differ much more 'from each other than the imagines do. The larva of the main- 

 form may be described as follows: 



Larva: Head rather large; subquadrate, a little broader than long; sides bulg- 

 ing; a notch at insertion of antennae; front margin arcuate. Antennae long, highly 

 arcuate; basal thirds rather thick, spinose; apical part slender, a large tuft inser- 

 ted remarkably near the apex; two long setae before apex; on apex itself a long 



