into two Classes. cciii 



among the Lepidoptera : in this case they reside at the bottom 

 of running streams ; they feed principally on decaying leaves 

 and other vegetable substances which fall into the water, but 

 also, as proved by Pictet, on other aquatic larvae : they are sup- 

 posed to breathe by means of external abdominal filaments, 

 which, in some of the species, are separate and very conspicu- 

 ous, in others they are grouped in bundles, but their office is 

 rather assumed than proved. 

 Pupa necromorphous : when arrived at its full growth, the larva 

 spins, by means of an oval spinneret like that of the silk-worm, 

 an open net across both ends of the case, and this allows the 

 pupa, which possesses the same (supposed respiratory) filaments 

 as the larva, to breathe by separating oxygen from the water 

 which passes freely through the case ; the posterior extremity is 

 firmly attached to some stick, stone, or other substance, at the 

 bottom of the stream : in figure the pupa closely resembles the 

 imago, all its limbs being discernible : when the time arrives for 

 its assuming the imago state, the mandibles are first liberated 

 from their investing membrane, and with these it gnaws an open- 

 ing in the net- work at the anterior extremity of the case, and its 

 specific gravity being less than that of water, it soon emerges 

 altogether from the case, and rising to the surface there floats, 

 until propelled by the casualties of winds or currents to the shore, 

 when, by means of its liberated fore-legs, it crawls up a twig, 

 a blade of grass, a stone, or other convenient object, and there 

 completes its metamorphosis. 

 Imago with small exserted head; very long, filiform, multiarticu- 

 late antennae ; distinct, lateral, hemispherical eyes ; three epi- 

 cranial ocelli ; the palpi long, porrected, and conspicuous ; the 

 other cibarian organs mere rudiments; the prothorax atrophied; 

 the wings dissimilar, almost revolute, of nearly equal size, the 

 hind wings folded longitudinally; the legs long, the tibiae spur- 

 red ; the body and wings covered with hair, and the entire figure 

 and habit resembling the Tineina amongst Lepidoptera : the 

 flight is generally slow, in theeyening, and for a short distance ; 

 the life short ; the food none. 

 This group is the only one amongst the Stegoptera which has been 

 thoroughly worked : the task has been admirably executed by M. 

 Pictet, of Geneva. The following formula, although based on cha- 

 racters of the larva and pupa, is confirmed and supported by those 

 of the imago. 



