148 NATURAL HISTORY. [cH. IX 



pendages, fringed on their sides with fine hairs. 

 When the larva wishes suddenly to change its po- 

 sition in the water, or dart from the approach of 

 some larger insect or animal, which might devour 

 it, the insect gives a prompt vermicular movement 

 to its body, striking the water with its tail, the 

 fringe of which then becomes very useful to the 

 animal, since the tail is thereby rendered more fit 

 to resist the water, and to cause the insect to ad- 

 vance. The head is rather flat, armed in front with 

 a pair of very strong, long, and curved jaws, which, 

 when magnified, appear to have at their apex an 

 aperture or an oblong hole, through which the in- 

 sect sucks, by little and little, all the solid parts of 

 its prey, which generally consist of other larvae. 



They are even bold enough to attack water-newts 

 and tadpoles, and have been known to seize a young 

 tench of three inches in length, and to kill it in the 

 space of a minute : they are, therefore, considered 

 as one of the most mischievous animals that can 

 infest a fish-pond. The singular form of the larva 

 caused it to be considered by ancient authors as 

 analogous with the shrimp tribe, and it has actually 

 been referred to that series of crustaceous insects 

 under the denomination of Squilla aquatica. When 

 arrived at its full growth, the larva forms itself an 

 oval hollow cocoon, made of soft earth or clay, 

 collected from the banks of the water it inhabits ; 

 in a few days it changes into a chrysalis, which is 

 of a white colour. After the space of three weeks 

 it undergoes the last metamorphosis, as represented 

 in the right-hand figure. 



The perfect insect is rather more than an inch 

 long, of a blackish olive colour, with the outer mar- 

 gins of the neck and wings bordered with yellow. 

 The two sexes of this insect are easily distinguished 

 from each other. The male is known not only by 

 the smoothness of the wing-cases, but also by the 

 breadth of the fore-feet, which are abbreviated and 



