STATES OF INSECTS. 233 



monly form their cocoons of the substances I have indi- 

 cated ; but when by any cause they are prevented from 

 access to them, they often substitute such other materials 

 as are at hand. Reaumur fed a larva that formed its 

 cocoon of minute fragments of paper, which with its 

 mandibles it had cut from the piece that covered the glass 

 vessel that contained it a : and the same circumstance 

 happened to Bonnet. 



Upon a former occasion I described to you the cases 

 of various kinds formed and inhabited by the insects of 

 the Trichoptera Order {Phryganea L.) commonly called 

 case-worms b . As these serve for the pupa as well as 

 the larva, they may be regarded as a kind of cocoon. I 

 shall not repeat here what I then said ; but having pur- 

 chased from the collection of the late Mr. Francillon 

 some that seem to belong to this or some cognate tribe, 

 that are of a curious construction, I shall give you some 

 account of two or three of them in this place. The first 

 is not quite thi-ee inches long, of a sublanceolate shape, 

 but rather widest towards one end. It consists of an in- 

 ternal tough and thick bag or cocoon, of a silk resem- 

 bling fine wool of a dirty white colour, which is closely 

 covered transversely by pieces of the stalk of a plant, 

 about three-fourths of an inch in length, and crossing 

 each other at an obtuse angle. The next is thicker and 

 shorter: the internal bag is just covered with small frag- 

 ments of wood like sawdust ; over these are fastened ir- 

 regularly, short stout pieces of a pithy stick or stalk, and 

 the whole is clothed with a very close-woven ash-co- 

 loured web. It seems difficult to conceive how the in- 

 closed animal could contrive to cover her habitation with 

 a Reaum. i. 540. b See above, Vol. I. 167—. II. 264. 



