MANUAL OF NATURAL HISTOEY. 217 



for themselves a curious little house of shells, small 

 pieces of stick, and other such materials, kept toge- 

 ther by threads similar to those spun by caterpillars ; 

 in this tube-like home they dwell, at the bottom of 

 streams, and in it undergo their metamorphosis into 

 the pupa, state ; when about to assume the perfect 

 form they crawl out of the water up the stem of 

 some plant, cast their exuvia, and become denizens 

 of the air. 



Thus, from forms singular, grotesque, and most 

 unlike, proceed those which can scarcely fail to ar- 

 rest our gaze and excite our admiration. 



Y. ORDER. ROOF-WINGED INSECTS (Stegoptera). 



Wings four, large, membranous, often beautifully 

 reticulated, frequently dissimilar, deflexed when not 

 in use, never carried erect, seldom porrected, ante- 

 rior pair sometimes hirsute, posterior generally folded 

 when at rest ; antennae more or less lengthened, 

 filiform, multiarticulate, sometimes pectinate, occa- 

 sionally shorter and clavate ; abdomen usually of 

 moderate length and cylindrical; legs often long 

 and slender. 



1. FAMILY. Scorpion-Flies (Panorpidse). Head 

 produced into an elongated deflexed rostrum ; 

 eyes prominent ; antennae long, slender, many 

 jointed ; anterior segment of thorax forming 

 a narrow collar ; body slender, posterior seg- 

 ments of abdomen narrowed, the last segment 

 in the males sometimes armed with a pair of 

 forceps ; wings variable, sometimes porrected 



