226 



Microscopical Essays. 



The tail ferves the larva both for the purpofes of fwimming 

 and breathing, and it receives through the tail that which is the 

 univerfal principle of life and motion in animals. By means of 

 thefe hairs it can flop itfelf at pleafure when fwimming, or 

 remain fufpended quietly in the water for any length of time. 



The motion of this infect in fwimming is very beautiful, efpe- 

 cially when it advances with it's whole body floating on the fur- 

 face of the water, after filling itfelf with air by the tail. To fet 

 out, it firft bends the body to the right or left, and then contracls 

 it in the form of the letter S, and again ft retches it out in a 

 {trait line : by thus alternately contracting and then extending the 

 body, it moves along on the furface of the water. It is of a very 

 quiet difpofition, and not difturbed by handling. 



Thefe larva are generally to be found in fhallow Handing 

 waters, about the beginning of June, fooner or later as the fum- 

 mer is more or lefs favorable ; in fome feafons they are to be 

 found in great numbers, while in others it is no eafy matter to 

 meet with them. They love to crawl on the plants and grafs 

 which grows in the water, and are often to be met with in ditches, 

 floating on the furface of the water by means of their tail, the 

 head and thorax at the fame time hanging down ; and in this 

 fituation they will turn over the clay and dirt with their fnqut and 

 feet in fearch of food, which is generally a vifcous matter that 

 is common in final 1 ponds and about the fides of ditches. This 

 worm is very harmlefs, contrary to the opinion one might form 

 at firft fight, from the furprizing vibratory motion of the legs, 

 which refembles the brandifhings of an envenomed tongue or fl ing 

 They are moft eafily killed for difleBion in fpirit of turpentine. 



