788 



THE DIPTERA 



In the early morning the female flies to the nearest water and 

 lays her eggs. Usually she does not travel far, but is beheved to 

 be capable of going at least half a mile in case of need. 



The females of the Culicinse do not appear to concern themselves 

 as to the nature of the water in which they lay their eggs, but the 

 female Anophehnae prefer clean water with a certain amount of 

 weed. This water may be the back eddies of a river, where there 

 is the protection of weeds, or the margins of large lakes, where 

 dense surface vegetation is to be found, or any collection of water 

 which contains green vegetal matter, or, failing these, any collec- 

 tion of fresh or moderately salt water. Small and large wells are a 

 prolific source of mosquitoes, as are puddles, and water in broken 

 bottles, shells, and especially in plants like bamboos, etc. Having 

 laid the eggs, they retire to some dark corner during the daylight, 

 and emerge at night for another feed of blood. How long they live 

 is not known with certainty, and will be discussed, together with 

 other features of their bionomics, in Chapter XL., under Malaria. 



Mosquitoes can hibernate during the cold weather of the tem- 

 perate zone, and sestivate during the dry hot weather of the tropics. 



Fig. 396. — Girardinus pceciloides de Filippi. 

 (The tail should have been drawn expanded.) 



In this latter condition they bite and suck blood, but apparently 

 do not lay eggs, even if water is provided. The eggs are kept afloat 

 on the surface of the water by their structure, and in due course 

 give rise to the larvae, which are great eaters, living not merely 

 upon unicellular organisms, such as algae and diatoms, but also 

 upon their fellows. For purposes of obtaining air they are com- 

 pelled to come to the surface of the water. The Anopheline larva, 

 not possessing a siphon, has to lie more or less parallel with the 

 surface of the water in order to enable the air to enter the spiracles, 

 and this it is able to do by the aid of the palmate hairs already 

 mentioned; while the Culicine larvae have merely to bring the 

 apex of the siphon to the surface of the water, from which they 

 apparently hang downwards. Larvae are certainly able to hiber- 

 nate, and perhaps eggs also. The pupa does not feed. 



Mosquitoes have many enemies and parasites, but the most 

 important from a point of view of the prophylaxis of malaria are 

 those which eat the eggs, the larvae, and the pupae, of which fish 

 are the most important. 



In 1905 C. K. Gibbons pointed out that a small fish, popularly 



