1S74.] 



199 



and leaving no trace of its former existence beneath, on the eyes of 

 the perfect Volucella. 



The structure of the wall of the hollow tube of the head appen- 

 dage, showed, after slight maceration and under a quarter-inch object 

 glass, as externally slightly corrugated, with a 

 series of round or pointed oval pits or pores, 

 arranged irregularly, but for the most part 

 in parallel lines round the tube. On the in- 

 side, the wall of the tube was set with minute, 

 spine-like growths (as at Fig. 7), straight, or 

 slightly curved in shape, these projecting into 

 the hollow of the horn-like tube, and, like the 



external pits or pores, set for the most part in lines round it. The 

 intervening structure between the inner and outer coats of the tube 

 wall showed as formed of fibres, or tubes, very 

 irregular in their course, and frequently anas- 

 tomosing (Fig. 8), of various sizes, and with 

 markings on them coinciding, apparently, with 

 the position of the pits on the external coat. 



During the growth of the pupa in its case, 

 although it was (after the early part of its 

 change) firmly fixed in place by these tubular 

 head appendages, yet there did not appear to be any connective 

 growth between them and the pupa-case (formerly the larval skin) : 

 they could be withdrawn through it, like a finger from a ring, leaving 

 a neat circular aperture at their point of passage ; and from this 

 circumstance, and the various details, it appears as if the growth of 

 the head-tubes began at the time of the pupal change from the larval 

 state, and that the horns forced their way through the hardened case, 

 and remained fixed there, the internal tissue connected with them 

 breaking up just before the full development of the fly in the 

 puparium. 



Their use I conjecture to be as a temporary breathing apparatus ; 

 the external pits, and the anastomosing internal tissue (conjecturally) 

 supplying the place of the organs contracted and clogged by the 

 change in the skin, and by the various accumulations of matter 

 probable during the long winter quiesconce of the larvffi in their 

 immovable stage of existence. 



Looking on the experiment as a whole, it appeared that the 

 Voliicellce larva? lost their power of feeding, and much of their power 



