20 
A Monograph of Culicidae. 
position by the aid of the gnat’s legs. They are not very firmly 
united, and may be readily separated from one another, and fall 
apart directly the larvae have escaped. In length these “ rafts ” 
vary from one-fifth to one-third of an inch ; the “ rafts ” float 
freely on the surface of the water. These egg masses are of 
irregular form, the most common being an elongated spindle- 
shaped mass (Fig. 15). In the case of C. pungens* they are laid, 
according to Professor Howard, in from six to thirteen longi¬ 
tudinal rows, with from three or four to forty in each row. The 
lower part of the “ rafts ” are freely submerged, the larger and 
thinner-shelled end of the eggs being in the water so that the 
developing embryos can obtain a supply of oxygen from it. It 
is almost impossible to keep these egg masses below the surface, 
as they are so buoyant. If they are kept completely immersed 
the larvae never develop. When first laid the ova are white, but 
they soon become grey in colour and at times have a greenish 
tinge. In the case of C. pungens they are dark greyish-brown at 
the tip, whilst the rest of the egg is dirty white. 
C. pipiens ova measure 0*9 mm. in length, C. nigrifulus O’6, 
and according to Howard those of C. pungens (= C. fatigans, 
Wiedemann?) 0*7 in length and 0*16 in diameter. 
As soon as the larvae escape from the lower end of the eggs 
the “ rafts ” break up. 
From personal observations I find that the eggs of both C. 
pipiens and ( 7 . nigritulus are laid soon after sunrise and also at 
dusk, especially when the weather is warm and still. 
Professor Howard also found that C. pungens laid its eggs 
in buckets placed out at nights, the eggs being found at eight 
o’clock in the morning, and, as he says, were probably laid in 
the early morning, before daylight; but the exact time of course 
was not noticed. 
Giles | states that the eggs are laid between five and six in 
the morning, and that the larvae escape in two or three days. 
This latter point I have not found to be the case ( vide p. 54). 
The female whilst depositing her eggs settles upon some 
small twig or leaf, holding on to it by her fore and mid legs, 
crossing the hind legs behind her, and drops the eggs between 
them, guiding them into position by their movements. 
The eggs of Culex vary slightly in form in the different species. 
The most common type in Culex is, however, narrowed gradu- 
* Bull. 25, New Se. U.S. Dept. Agriculture, p. 23. Howard, 1900. 
f Hd.Bk. of Gnats, p. 83. 
