t 

 2l6 FLEAS, FLUKES AND CUCKOOS 



of the water, crosses her long hind legs near their extremities, and 

 extrudes her eggs which are covered with adhesive cement, 

 within the V-shaped mould thus formed. Each raft consists of 

 200 to 450 eggs and she may produce five or six rafts during her life. 

 Culex pipiens lays on clean or foul water, in butts and tubs, tanks, wells, 

 ditches, pond margins and stagnant puddles contaminated by farm 

 manure or urine. Eggs are also deposited in pools in salt marshes 

 providing they do not contain more than half sea-water. 



Gnat larvae (Plate XXXc) are aquatic and sometimes occur in 

 vast numbers. It was once estimated that 400,000,000 were present in 

 two acres of Hampshire flood water, only a couple of inches deep. They 

 feed by whirling minute particles of food into their mouths by oscillating 

 a brush-hke moustache, or by chewing up vegetable or animal matter — 

 including one another if they get the chance. After moulting three 

 times the larva pupates. The pupa is also aquatic and, like the larva, 

 floats near the top of the water with its respiratory trumpets piercing 

 the surface film. 



The males hatch first. During the summer they dance their lives 

 away and die when the cold weather sets in. Their mouthparts are 

 poorly developed and they cannot suck blood and are limited to a diet 

 of fruit juice and nectar. It is easy to distinguish a male from a female 

 mosquito without the aid of a microscope as the male has feathery 

 antennae. In the human species it is man that has a deep voice but in 

 gnats conditions are reversed and the pipe of the male is several notes 

 higher than that of its mate. 



The female house-gnat requires a blood meal before she can lay 

 fertile eggs and her chief victims are birds, although she will occasion- 

 ally bite frogs and snakes and even mammals. In captivity her tgg output 

 is trebled if she is fed on bird's blood. Certain species ofAedes have been 

 known to migrate thirty miles inland from the saline marshes where 

 they breed, presumably in search of a blood meal. They subsequently 

 return to the marshes to lay eggs. The distance covered is known 

 accurately, owing to the re-capture of marked specimens. Culex pipiens 

 will also supplement her diet by feeding on nectar, milk standing in 

 pans, and even port wine. In the modern dairy the separator has 

 deprived them of their chief source of milk, as a thick layer of cream on 

 top appears to be an essential condition of feeding. Piercing the cream 

 to get at the hquid beneath seems a satisfactory substitute for piercing 

 the skin of a vertebrate animal to reach the blood below. When feeding 



