INSECTS DIPTE11A DIAGRAM 6 



143 



masses, and resemble a little boat floating on the water. The 

 larvre are aquatic, and swim by jerks by doubling themselves up. 

 They rise to the surface with their head downwards. They 

 breathe by the extremity of the body, where the trachese open. 

 The pupa* are also aquatic, and swim by jerks, "but may be 



Larva of Gnat 

 Magnified 



Gnat Magnified. Gnat. 



known by a kind of horns near the head. In their perfect state, 

 the gnats fly chiefly in the evening, and light upon men and 

 animals to suck their blood; they bury their sucker rapidly 

 under the skin, and the wound which they make remains painful 

 for some time, on account of the venom discharged into it. The 

 shrill noise which gnats, and especially mosquitoes make when 

 flying, is caused by the rapid motion of their wings, which strike 

 the air several thousands of times in a minute. 



Thefy. There are a great many different species of flies, 

 some of which have a fine blue or green metallic colour. In the 

 larva state the fly is called a maggot. Anglers use them to bait 

 their hooks. The blue flesh-fly lays its eggs on meat which is 

 beginning to decompose. The eggs are white, rather large, and 

 form in small clusters. The maggots which proceed from them 

 feed on the putrefying meat. When the time has come for them 

 to undergo their metamorphosis, they hide in dark and dry 

 places. When they have found a place that suits them, they 

 shrink up, turn brown, and thus become chrysalides without 



