430 THE NATURAL HISTORY 



spiracle is situated at the base of each, and the poisers 

 are often in rapid vibration even when the wings are 

 at rest. The insects of this order are so numerous, 

 both in species and individuals, and many of them are 

 so persistently obtrusive in their habits that they are 

 universally known, any attempt, therefore, to describe 

 their more obvious characters would, we imagine, be 

 superfluous, even to those whose entomological ex- 

 periences are limited to retaliatory measures on the 

 insects that annoy them. 



The family of Gnats is the first to come under our 

 notice, and Culex pipiens, the typical form, is dis- 

 tinguished by a slender rostrum nearly half as long as 

 the entire body of the insect, and enclosing no less 

 than six fine lancets, barbed at their free extremities. 

 When these are brought into use, an operation that is 

 very insidiously performed, an irritating fluid is in- 

 troduced into the wound they make, the unpleasant 

 consequences of which are felt long after the insect 

 has made its sanguinary attack. In their preparatory 

 stages gnats are aquatic, the larvae suspending them- 

 selves in their intervals of inactivity head downwards 

 in the water, and carrying on their respiratory functions 

 by means of a long tube projecting laterally from one 

 of their terminal segments, and furnished at its tip 

 with a star-like fringe radiating from a central spi- 

 racle. As often as a fresh supply of air is required 

 this fringe is expanded on the surface of the water, 

 and the breathing pore is thus brought into direct 

 communication with the atmosphere. In the next 

 stage there are two respiratory tubes, but as they are 

 situated on the anterior part of the body, the position 

 of the pupa in the water when at rest is exactly the 

 reverse of that of the larva in the same condition. In 

 about a month after the deposition of the eggs the 

 perfect insect appears, with a further modification of 

 its respiratory system, and, taking its stand on the 

 skin it has just quitted, it securely floats on the suface 



