LAETiE OF WATEE-PLIES. 269 



apparatus, whicli partly consists of thirty feathery Lairs 

 surrounding a small orifice connected with the tracheal system. 

 These hairs can be opened and closed at the wiU of the 

 animal. While expanded they are very star-like. When 

 the creature wishes to take in a fresh supply of air, it ascends 

 to the surface of the water hy means of a wriggling motion, 

 and there it spreads out its bronchial plumes : these act not 

 only as a float to support the animal in the water, head 

 downwards, but are also so constructed as to repel the water 

 and to admit the air into the orifice which they surround. 

 As soon as the larva has obtained sufficient air, it folds the 

 plumes, which then inclose a small globule of air, and 

 this is carried by the animal to the bottom of the water. 

 This larva obtains its food in the same way as does that of 

 the gnat. A cun-ent of water, owing to the formation and 

 the movements of parts of the head, is made to set in towards 

 the head, carrying with it the minute animals and particles 

 of matter which form the creature's food. The pupalhood 

 of this animal is passed within the larval skin. The pupa 

 only occupies the broader and anterior portion of this envelope, 

 and in it floats until it changes into the perfect insect. The 

 imago is a little more than ^in. long, and it has a broad flat 

 brassy-black body marked with yellow. 



An insect belonging to the family Syrphidce, known as 

 the Drone-fly (Eristalis ienax), has a very curious larva; 

 or, rather, is a very curious creature during its larval state. 

 This larva is called the " rat-taUed larva," and is very common 

 in stagnant water. The late Rev. J. Gr. Wood, speaking of 

 these larvse, says : " The largest assemblage of these creatures 

 that I ever saw was in Wiltshire. A tub had been sunk 

 in the ground for the reception of water, and had gradually 

 become half-filled with dead leaves and other debris, which 

 decomposed into soft mud. This mud was so closely packed 

 with the larvcE of the Drone-fly that the water was quite 

 choked with them." This larva is shaped somewhat like a . 

 " maggot," with a long tail. The tail is composed of two 

 segments, one of which fits inside the other after the manner 

 of the joints of a telescope. The respiratory organs pass 



