576 DIPTERA. 



Cabcll.* Kollar alludes to the unchanged condition of the 

 insect within this case, in the European specimens which 

 he had examined.! Mr. Westwood makes the following 

 remarks upon some from Vienna that were in his possession : 

 " The insects are enclosed in a leathery case, and on open- 

 ing them I discovered the larvae shrivelled up and dead." J 

 Referring to Mr. Say's account of the Hessian fly, and its 

 flax-seed case, Mr. Westwood says, " It is not described in 

 what manner this case is formed." That it really consists 

 of the loosened outer skin of the maggot is evident from its 

 shape and structure. It has nearly the same form and size, 

 is convex on both sides, and retains traces of the former 

 segments 4 in the transverse lines wherewith it is marked. 

 This flax-seed shell has been correctly called a puparium, 

 or pupa-case, because the pupa is subsequently matured 

 within it. 



Dr. Chapman repeatedly alludes to the pupa, or chrysalis 

 as he calls it, and to " the outward coat " of the larva " be- 

 coming a hard shell or covering for the chrysalis"; by which 

 we perceive that he was acquainted with the origin and 

 office of the one, and the condition of the other. But as the 

 true figure of the included insect is concealed, and cannot 1 

 be determined without opening the puparium, " it is custom- 

 ary," as stated by Messrs. Kirby and Spence, " in speaking 

 of pupae of this description, to refer solely to the exterior 

 covering." Agreeably to this common usage, sanctioned by 

 the best entomologists of our time, the flax-seed case, or 

 puparium, has been commonly denominated the pupa, even 

 by such writers as Mr. Say, to whom the real nature of its 

 contents must have been well known. 



In the letter before mentioned, Mr. Herrick thus contin- 

 ued his account of the transformations of the insect. " The 



See page 667. 



t Hollar's Treatise, p. 121. 



Note in Hollar's Treatise, p. 121. See also Westwood's Modern Classification 

 of IiMecta, Vol. II. p. 620. 

 t Introduction to Entomology, Vol. HI. p. 268. 



