OF WASHINGTON, VOLUME XIII, 1911. 39 



an invaginated and shrunken bladder, one can determine by the exam- 

 ination of the head of the imago whether the fly does or does not 

 burst open the puparium by means of a frontal bladder without it 

 being necessary to directly observe the emergence. One can best de- 

 termine the conditions by longitudinal sections carried medianly 

 through the head. 1 



He then makes comparison, accompanied by figures, of the 

 structure in Cattiphora on the one side and of various Syrphi- 

 dae on the other. He shows that while the invaginated ptili- 

 num is present in Calliphora it is absent in the Syrphidae, 

 Pipunculidae, Platypezidae, and Phoridae. He points out that 

 the frontal lunule, which is still present and well marked in 

 the Syrphidae, is only indicated in the Pipunculidae and Platy- 

 pezidae by somewhat heavier chitinization and darker color- 

 ing, while in Phora there is no indication whatever. 



It appears, however that Becher, in criticizing the work 

 of Kunckel d'Herculais, had but a superficial knowledge of it. 

 Kiinckel d'Herculais enters particularly into the transient 

 character of the frontal bladder in the Syrphidae and contrasts 

 this with its persistence in the higher flies. 



When the bladder is entirely inflated a well-marked circular ridge 

 indicates the line which separates it from the vertex and the cheeks; 

 when, on the contrary, it is completely withdrawn into the interior of 

 the head, the fly having reached its full development and the antennae 

 having taken their normal position, there does not remain more than 

 a slightly evident trace of this ridge. The outward projection of the 

 frontal bladder is accompanied by a general dilation of the entire 

 head, which at this time possesses a remarkable elasticity; the eyes 

 themselves are alternately moved nearer together or farther apart, 

 and, what is more incredible, undergo modifications in their curvature 

 as they approach each other towards the median line in consequence 

 of the tension or the relaxation of the vertex. The parts which sup- 

 port the base of the proboscis inflate also, and on each side one sees 

 come forth from the interior of the mouth-frame (mouth-opening) a 

 very small bladder; the inflation and retraction of these bladders is 

 accompanied by the extension of the proboscis and by movements of 

 the maxillary palpi. The inflation of the frontal bladder and the 

 buccal bladders sometimes reaches such a volume in certain Volucella 

 and some Mu.sca, when an obstacle opposes their emergence, that the 



1 L. c., p. 50. The opinion that the frontal bladder is absent in the 

 Syrphidae is reaffirmed by Brauer, who evidently had inspired Becher. 

 He states of the Syrphidae: "Die Fliege sprengt die Tonne durch 

 Ausdehnung und Entwicklung des meist langen Untergesichtes und 

 hat keine Stirnblase (Brauer, Becher)." (Denkschr. d. math.-natur- 

 wiss. Classe d. kais. Akad. d. Wiss., Wien, vol. 47, 1883, p. 31.) 



