Warble Flies. A Further Contribution on the Biology of Hypoderma lineatum and Hypoderma bovis

Extract

The experiments with warble-fly larvae, taken in conjunction with the evidence of Carpenter and Gläser, lend support to the view that they gain an entrance through the skin.

The hypothesis is advanced that the larvae select the gullet for reasons connected with their development and growth. These may be: a freer supply of oxygen, and a loose areolar tissue which offers comparatively little resistance to them.

The position of the larva under the hide is horizontal. In this position the skin movements affect it but slightly, or less than if the position were perpendicular.

H. lineatum does not terrify cattle as does H. bovis, the fly was seen ovipositing and the animals showed little uneasiness during the process.

The seasonal activity of H. lineatum is earlier than that of H. bovis.

Observations were made on oviposition which confirmed those of Riley and Gläser.

Two experiments were tried with larvae, to see if they would penetrate the hide, but no definite results were obtained.

Further proof is afforded of the terror which H. bovis inspires in cattle. It was observed that animals, exhausted by running, occasionally lay down and became more or less indifferent to the attacks of the fly. On these occasions the eggs were laid higher up on the host's body.