38 THE INSECT WORLD. 



ought not to cause any pain. " The point of the finest needle," says 

 Rdaumur, " compared to the sting of the gnat, is the same as the 

 point of a sword compared to that of the needle." How is it then 

 that so small a wound does not heal at once ? How is it that small 

 bumps arise on the part that is stung ? The fact is, that it is not 

 only a wound, but it has been imbued with an irritating liquid. 



This liquid may be seen to exude, under different circumstances, 

 from the trunk of the gnat, like a drop of very clear water. 



Re'aumur sometimes saw this liquid even in the trunk itself. 

 " There is nothing better," he observes, " to prevent the bad effects 

 of gnat bites than at once to dilute the liquid they have left in the 

 wound with water. However small this wound may be, it will not 

 be difficult for water to be introduced. By nibbing, it will be at 

 once enlarged, and there is nothing to do but to wash it. I have 

 sometimes found this remedy answer very well." 



The gnat is not always in the form of a winged insect, greedy for 

 our blood. There is a period during which they 

 leave us in repose. This is the larva period. It 

 is in water, and in stagnant water in particular, 

 that the larva of the insect which occupies our 

 attention is to be found. It resembles a worm, 

 and may be found in ponds from the month of 

 May until the commencement of winter. 



If we desire to follow the larva of the gnat 

 from the beginning, we have only to keep a bucket 

 of water in the open air. After a few days this 

 water will be observed to be full of the larvae of 

 the gnat (Fig. 28). They are very small, and 

 come to the surface of the water to breathe ; for 

 which purpose they extend the opening of a pipe, 

 A, which is attached to the last segment of the 

 body, a little above the surface. They are, con- 

 sequently, obliged to hold their heads down. By 

 the side of the breathing-tube is another tube, B, 

 shorter and thicker than the former, nearly per- 

 pendicular to the body, its orifice being the exterior 

 termination of the digestive tube. At the anus it 

 is fringed with long hairs, having the appearance, 

 when in the water, of a funnel. At the end of the same tube, and 

 inside the hair funnel, are four thin, oval, transparent, scaly blades, 

 having the appearance of fins. They are placed in pairs, of which 

 one emanates from the right side, the other from the left. 



Fig. 28. 

 Larva of the Gnat. 



