LIFE HISTORY AND SEASONAL PREVALENCE 131 



Meinert states that the larvae of Mochlonyx affect the 

 waters of fields and woods, and that they are especially often 

 found in such places as ditches, where the water is clear, 

 but without any particular current. The larvae do not sur- 

 vive the winter, but he considers it probable that the eggs 

 do, as he has found newly-hatched larvae so early in the year 

 as to make it highly improbable that any of the perfect 

 insects could have emerged from their hybernation, even 

 assuming that the adults do hybernate. In a warm room, 

 in captivity, all the changes from egg to imago were gone 

 through in three weeks. Unlike Culex there appears to be 

 only a single generation of larvae developed in the year. 

 The position taken up by the larvae is very like that of 

 Corethra, but they are more in the habit of remaining 

 under water. They are voraciously carnivorous, and appear 

 to be even more arrant cannibals than the larvae of that 

 genus. The pupa also behaves much like that of Corethra, 

 but it is not quite so rapid in its changes of skin. 



The larvae of the CulicidfP- swarm in spring and summer 

 in the stagnant water of tanks and other domestic collections 

 of water, where they may be found in abundance in Europe 

 from the time the ice is melted. Usually they keep at 

 the surface of the water or a little below it, in an inverted 

 position, the head being lowest, breathing by means of the 

 tube placed at the extremity of the abdomen. They are 

 extremely lively and easily disturbed by any movement of 

 the water, but soon resume their old position. Their body 

 is elongated and has no legs. At first greenish, they soon 

 become greyish and transparent. The larva undergoes 

 several moults, three taking place in the first two or 

 three weeks. In order to get rid of the old skin it places 

 itself horizontally on the surface of the water with the back 

 upwards. As a rule the change takes place through a rent 

 on the thorax, and extends after to the abdominal segments. 

 Like the larva the nymph is capable of swimming but 

 can take no nourishment. When in repose it is contracted 

 into a lenticular form, its abdomen being bent under the 

 thorax and kept closely applied to it. It lies vertically in 

 the water but in a different sense from the larva, as the 



