198 



[February, 



were other apecimens which, taken from the puparia in varioue states 



of development, showed the growth of the head appendages in an 



almost complete series. 



The first occasion on which I noticed these appendages (or horns) 



was on a Volucella pupa so far formed that it was easily removable, 



save at the caudal extremity, from the puparium, but still very soft, 



and only partially developed : here the horns adhered entirely to the 



pupa, and I did not notice any external signs of them on the 



puparium. 



A more advanced specimen was fixed by the horns to its case, 



these horns being now visible externally ; and this adhesion continued 



till the development of the fly, when the black, horn-like appendages 



remained outside the emptied puparium, and the perfect fly showed 



no trace of their former presence. 



Examining their structure, they appeared in the early stage, and 



to a careful general inspection, to be simply white, like the developing 



insect, with brown tips, and, when further advanced in age, as two 



tubes set immediately over the top of the back of the head, each horn 



with its basal appendage at the highest angle 



of the eye of the insect. Fig. 5 gives a side 



view of one of these horns with the eye of the 



pupa beneath. These tubes were of white 



pitted or porous tissue, passing forwards and 



upwards under two perfectly transparent, 



bladder-like growths (which almost touched 



each other on the summit of the head), and, 



on leaving the bladder and growing through the puparium, ap- 

 pearing externally as dark coloured tubercu- 

 lated club-like excrescences, as drawn much 

 magnified in Fig. 6, in which the part above 

 the dotted line represents the portion pro- 

 jecting beyond the pupa-case. The club itself 

 showed (Fig. 4) as much tuberculated and 

 punctate, slightly hairy at the extremity, black 



in colour, and joined by a ring of brown to the hollow tube of white 



pitted tissue. 



On approaching maturity (in a specimen examined after death), 



the transparent tissue changed to a confused mass of fine threads, 



easily removable as a sheet, with the neighbouring portions of pellicle, 



