Genus Culex . 
135 
Observations. —The type taken as that of Culex pipiens, L., 
has many closely related species. That variable species, which 
I have taken to be C. fatigans of Wiedemann, is very closely 
related to our common European gnat, but I am sure they are 
quite distinct. In all the Culex pipiens I have examined, both 
from Europe, Malta, and North America, the stem of the first 
sub-marginal cell is abnormally short for the very long cell, 
and the abdominal banding is of a constant flaxen-yellow colour. 
The character of the first sub-marginal cell and its stem is one 
by which the species is best identified. 
Culex pipiens is subject to great variation in size and also in 
regard to certain features of its venation. 
I have known it to vary from 4 to 6 mm. in the 9 sex. 
This difference in size can be produced artificially by excess 
or absence of food. Two batches of larvae from the same 
egg-raft were kept, one in distilled water, fed only now and 
then, the other with a plentiful and constant supply of food, 
the difference in length being in some specimens 2 mm. 
The venation varies in regard to the relative position of the 
posterior cross-vein. Usually in the 9 it is about its own 
length distant from the mid cross-vein, but in some specimens 
it is not half its length distant, in others nearly twice its length 
away. 
In one specimen photographed for me by Mr. Hammond the 
venation differed in this respect in the two wings (Fig. 221, 3 and 
4), but beyond this the nervures of Culex pipiens are very 
constant and very characteristic. 
The 9’s hibernate in cellars and outhouses, and appear mostly 
in March and April, but do not, as far as my observations go, 
deposit their eggs for some little time. No males are to be 
found in the early part of the year, the females having been 
fertilised by the males in the previous autumn. I have known 
this gnat active in numbers well into November in England, and 
they occur during the winter in houses. The larvae are found in 
rain barrels, cisterns, and small pools, or any receptacle where 
water will collect. The first lot of larvae seem to mature in 
June, and from then they go on appearing until October. One 
may find larvae of all sizes in the same vessel. This species is 
known to bite some years with considerable severity. 
Synonymy. —I have examined Bigot’s type of C. agilis from 
Algeria, now in Mr. Yerrall’s possession, and find it is only 
Culex pipiens. 
