426 



NATURAL HISTORY OF ARTHROPODS. 



lfiG. 536. Cuterebra buccator, dorsal aud side views. 



North America, and is said to be the cause of the deer rubbing themselves in spring to 



such an extent as to wear off the darker hair, and thus change their appearance. 



Species of (Estrus live in the frontal and nasal cavities of sheep and various antelopes. 

 Cephalomyia lives in the nasal fossa? and throat of the camel; Pharyngomyia and a 



number of species of Cephenomyia in the fauces of various species of deer. Moyeri- 



hofera grandis lives under the 

 skin of a South American mouse 

 (Hesperomys). Cuterebra emas- 

 culator lives in the male organs 

 of species of Tamias, and de- 

 rives its specific name from the 

 effects it produces upon these 

 glands ; other species of this 



genus occur in the skins of rabbits, gophers, and opossums. Species of Dermatobia 



infest the skins of dogs, cattle, Felis concolor, Cervus rnfus, monkeys, and even man 



himself. 



It will be of interest to trace the habits in detail of some of the more important, 



for which I am mostly indebted to Brauer, to whom our chief knowledge of this family 



is due. 



The female of the common horse bot-fly, Gastrophilus equi, when her eggs are 



ready for deposition, seeks a horse, or an ass if it be either of the species peculiar to 



this animal, and, flying slowly about, holds her body nearly upright, with the elongated 



ovipositor directed downwards and inwards. When she has found the proper place to 



deposit the egg she remains for a second in this upright position, then flies suddenly 



away for a short distance, leaving the single egg attached to a hair, with its larger end 



directed outward. In a few moments another egg 



is ready and this operation is repeated, always 



choosing the same part of the body, which is 



usually on the front and inner side of the knees. 



They are attached to the hair by means of a fluid 



substance which quickly dries and holds them 



firmly. In this way from four to five hundred 



eggs are laid, and they are by no means placed at 



haphazard in any place, for their future existence 



depends upon their being in such situations as the 



horse can easily reach with his lips. It is a curious 



instinct which teaches horses that these insects are 



to be avoided; although the fly can cause little 



irritation in the process of laying her eggs, yet 



the horse will twitch the skin each time, and will show the utmost annoyance, often 



becoming unmanageable. 



In a few days the eggs hatch, leaving the shells still firmly fastened to the hairs, and 



the young larva? are then conveyed to the mouth of the horse when biting or nipping 



such parts as are irritated. It is thus the more interesting to observe that the eggs 



are usually laid on such portions of the body as are most accessible to the animal's 



mouth, although it is believed that the young larva? may reach the mouth by their 



own activity. They are swallowed with the food, and, upon entering the stomach, 



attach themselves to the inner membrane by means of the booklets that encircle the 



IMG. 53'. Gastrophilus equi, horse bot-fly, 

 aud a, larva, enlarged. 



