142 TRICHOFTERA. 



they undergo their transformations, form some of the most 

 beautiful objects of contemplation in connection with the 

 natural history of these insects. 



In the struggle for existence continually raging beneath 

 the waters, with a fury perhaps surpassing that on land, the 

 soft helpless larvae of the Pliryganidce would soon fall an 

 easy prey to voracious fishes, to which they are notoriously 

 hons morceaux, and to the numerous predaceous insects, both 

 perfect and larval, that share with them the occupancy of the 

 waters, were they not endowed with the ingenuity to construct 

 around them a fortress, in many instances portable, which 

 they inhabit, and into the innermost part of which they retire 

 on the least appearance of danger. As the method of con- 

 struction of these '^ cases," as they are commonly and not 

 inaptly termed, varies much, it has occurred to me that a 

 short sketch of the descriptions of cases made by the various 

 genera would be acceptable to the readers of the "Annual." 



In commencing, it may be as well to remark, that the 

 Trichoptera are usually divided by modern writers into 

 seven families, viz., JPhrycjanidoi, LimnephilklcB^ Sericos- 

 tomidce, HydroptilidcBf Leptoceridce , Rhyacojihilidce, and 

 SydropsyclLidce, and for convenience in my present purpose 

 these families may be divided into two groups, the first con- 

 taining the first five families, and the second the two last ; 

 thus, 



1. Case forming a complete tube around the body of the 

 larva ; often portable and carried about by its inhabitant, or 

 fixed by one end or other parts to stones, &c. External form 

 generally more or less tubular. 



2. Case not forming a complete tube, but incomplete on 

 that side by which it is constantly fixed. External form 

 generally a more or less shapeless heap of small stones. 



The cases of the first group were known to the ancient 



