40 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



anterior region of the head surpasses the posterior in width and re- 

 sembles a small bladder ready to burst, so much is it distended by the 

 violent efforts of the insect. 1 



***** 



In Volucella, Eristalis, and Syrphus not a trace of the frontal blad- 

 der remains when the insect is ready to begin its flight; but in Musca, 

 Calliphora, Lucilia, and Sarcophaga the bladder is found in the in- 

 terior of the head as a fold of the skin having the form of a bag with 

 a wrinkled and rumpled envelope; its structure, aside from its trans- 

 parency and coloration, is identical with that of the surrounding in- 

 tegument: one sees the same lozenge-shaped scales. 2 



Kiinckel d'Herculais touches upon the transient character 

 of the frontal bladder in the Syrphidae again in criticizing 

 Lowne, who attributed to the frontal bladder the seat of the 

 olfactory sense and the faculty of producing the humming 

 noise. Kiinckel d'Herculais points out that the integument 

 of the sac is identical with that of the front of the head and 

 that the Syrphidae, while they have no frontal sac in the ma- 

 ture state, are nevertheless noted for their powers of sone- 

 faction. 



Becher, in addition to his studies on mature specimens, 

 also observed some live pupae and recently emerged Syrphidae. 

 While his conviction, gained from mature specimens, that 

 there is no frontal bladder in the Syrphidae and related fam- 

 ilies, led him into error, his observations nevertheless reveal 

 some interesting peculiarities in the condition of the head at 

 the time of emergence. 



After the lid of the puparium is burst off the head of the fly appears 

 and one can now see that, different from the remaining Cyclorrhapha, 

 it is completely developed and closed in the region of the front and 

 vertex, therefore above the antennae. On the contrary, the lower 

 face, which in the Eumyids remains unchanged, is here soft and trans- 

 lucent and, while in the developed animal it shows a convex, often 

 face-like, profile, immediately after emergence it is concave and 

 transversely split. On well-advanced pupae the concavity and trans- 

 verse folding can.be seen very plainly. The lower face and the later- 

 al parts of the head appear here by their expansion to assume the 

 function of the frontal bladder, to burst off the lid of the puparium, 

 and one also sees the lower face pulsate in a similar manner with the 

 frontal bladder, but without ever swelling to such a degree as this. 

 Only after the wings are expanded and hardened, and the proboscis, 

 which in the beginning lies folded back upon the breast, is withdrawn 



J L. c., p. 78. 

 2 L. c., p. 80. 



