20 GRAMMAR OF ENTOMOLOGY. 



full grown, it spins a little silken sheath, in shape 

 like a watchpocket, which is attached to the plant 

 which the larva frequents, and in which the larva 

 changes to a pupa in an upright position : the 

 case being always open at top, the head and 

 shoulders of the pupa are seen projecting above it. 



55. The pupa much resembles that of a moth : 

 it is perfectly motionless, of a brown colour, and 

 exhibits very distinctly the parts of the perfect 

 insect through its skin : from the back of its head 

 arise on each side four hair-like appendages ; 

 these are tubular, and appear to be designed for 

 breathing. 



56. About the sixth of July the little creature 

 bursts from its sheath ; the case of the chrysalis 

 opens in a right line down the back, and the 

 perfect insect emerges through the opening, sur- 

 rounded by a bubble of air, and slowly begins to 

 unfold its wings under the water ; finally, its skin 

 being cast, and its maturity attained, it disengages 

 itself from its former habitation, and mounts within 

 its bubble to the surface of the water, when the 

 bubble bursts, and the creature has acquired new 

 organs and a new element. 



57. The imago is a small black fly, with two 

 large transparent wings, which, when at rest, 

 repose horizontally on its back ; moderately long 

 legs, and short stout antennae ; it flies with ease, 

 and somewhat sportively, rising and falling. In 

 this country it is found in the damp parts of 



