NATURAL SCIENCES OF PHILADELPHIA. 41 



and some Geometree. It has been classed with the Psychidse by 

 Packard, and, owing to its near alliance to Heterogynnis, which 

 is removed by many European writers to the Zygaenidse, it has 

 been placed by Stretch in that group. One of the latter's reasons 

 for this removal is the resemblance which its larva holds to that 

 of Eudryas. But its habit of carrying the last segment elevated 

 in the air, which shows a certain affinity to some Nofodontas as 

 well as to Gerxira and Platypteryx, and of suspending itself by the 

 tail like the Geometrse, combined with the close resemblance which 

 the wings bear to some butterflies, renders it an interesting form. 

 The facts for the origin of butterflies herein embodied in connec- 

 tion with the above, aim to place it high up in Bombycidse. 



It has been suggested that the Sphinges are the remotely modified 

 descendants of a pre-existent Phryganea. It is well known that 

 the larva of the latter constructs a case into which it retires after 

 feeding. As this case with its inmate remains in its watery ele- 

 ment until the imago state is near at hand, if the argument previ- 

 ously advanced to prove the remote origin of the Sphingidse 

 through intermediate forms, from a Phryganea allied to existing 

 types, amounts to aught, we have in it a clue to the habit which 

 many of our Zygeenidse and Sphingidse possess of entering the 

 earth in assuming the chrysalis stage. The JEgeridse in their 

 larval stage bore into the stem of plants, and when ready to 

 pass into pupa?, construct oblong follicles, composed of small 

 fragments of barks and earth closely united together by the silk 

 of the animal. This style of cover is not essentially different from 

 that of the Sphinges and the Glaucopidians. As the ravages of 

 these insects are confined to the inner parts of plants, it is not 

 unreasonable to suppose that when the time for change arrives, it 

 will be undergone where there is least trouble and least outhoy of 

 strength, in the burrows created. The Zygeenidse, as a rule, sub- 

 sist upon the outer parts of plants On the supposition that some 

 pre-existing individual of this family had profited by a change 

 from outer to inner, it would be a comparatively easy matter to 

 trace the effects which a change of environment would impress 

 upon said individual. We might expect considerable alterations 

 in larval color, form, and structure, with but a trifling change in 

 cell-manufacture. 



In the condition of larvae the Trichoptera are vegetarians; but 

 will occasionally attack minute fresh-water animals when driven 



