The house fly : disease carrier an account of its dangerous activities and of the means of destroying it / by L. O. Howard.
- Leland Ossian Howard
- Date:
- 1912
Licence: In copyright
Credit: The house fly : disease carrier an account of its dangerous activities and of the means of destroying it / by L. O. Howard. Source: Wellcome Collection.
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![terior end of the pupal case in dorsal and ventral por- tions by means of the inflated frontal sac, which may be seen extruded in front of the head above the bases of the antennse. The splitting of the anterior end of the pupal case is quite regular, a circular split is formed in the sixth segment and two lateral splits are formed in a line below the remains of the anterior spiracular processes of the larva. The fly levers itself up out of the barrel-like pupa [puparium] and leaves the nymphal sheath. With the help of the frontal sac, which it al- ternately inflates and deflates, it makes its way to the exterior of the heap and crawls about while its wings unfold and attain their ultimate texture, the chitinous exoskeleton hardening at the same time; when these processes are complete the perfect insect sets out on its career.” The frontal sac just mentioned is the distended mem- branous portion of the front of the head. This is con- stantly distending as the fly walks rapidly about after issuing. When it is contracted at this early time, it forms a dull area, soft and fleshy-looking, and free from hairs. The fly possesses the power of distending it into a bladder-like expansion, trapezoidal in outline and almost as big as the rest of the head, pushing the antennse down out of sight. This membrane is evi- dently distended with air, and, as pointed out by Pack- ard, its connection with the tracheae and the mechanism of its movements would form a very interesting sub- ject of inquiry. Lowne, in his Anatomy of the Blow- fly, has described a similar structure with that insect,](https://iiif.wellcomecollection.org/image/b28050745_0062.jp2/full/800%2C/0/default.jpg)
