357 



QEsTUus, Lin., 



Which is very distinct, as in place of the mouth we find but three 

 tubercles, or slight rudiments of the proboscis and palpi. 



These Insects resemble large and densely pilose flies, and their hairs 

 are frequently coloured in bands like those of the Bombi, Their an- 

 tennae are very short; each one is inserted in a fossula over the front, 

 and terminated by a rounded palette with a simple seta on the back, 

 near its origin. Their wings are usually remote; the alulae are large 

 and conceal the halteres. The tarsi are terminated by two hooks 

 and two pellets. 



These Insects are rarely found in their perfect state, the time of 

 their appearance and the localities they inhabit being very limited. 

 As they deposit their eggs on the body of various herbivorous quadru- 

 peds, it is in woods and pastures that we must look for them. Each 

 species of CEstrus is usually a parasite of one same species of some 

 mammiferous animal, and selects for the location of its eggs the only 

 part of its body that is suitable for its larvae, whether they are to re- 

 main there, or pass from thence to the spot suited for development. 

 The Ox, Horse, Ass, Rein-deer, Stag, Antelope, Camel, Sheep and 

 Hare are the only quadrupeds yet known, which are subject to be 

 inhabited by the larvae of the CEstri. They seem to have an extraor- 

 dinary dread of the Insect when it is buzzing about them for the pur- 

 pose of depositing its eggs. 



The domicil of the larvae is of three kinds; we may distinguish 

 them by the names of cutaneous, cervical, and gastric, as some live 

 in the lumps or tumours formed on the skin, others in some part of 

 the interior of the head, and the rest in the stomach of the animal 

 destined to support them. The eggs that produce the first are deposited 

 by the mother under the skin, by means of a squamous ovipositor com- 

 posed of four tubes fitting one within the other, armed at the end 

 with three hooks and two other appendages. This instrument is 

 formed by the last annuli of the abdomen. These larvae, called taons 

 by the farmers, are not compelled to change their domicil, finding 

 themselves, when hatched, in the midst of the purulent matter 

 on which they feed. The ova of the others are simply deposited and 

 glued to various parts of the skin, either in the vicinity or the natural 

 cavities into which the larvae are to penetrate and take up their abode, 

 or on those spots which the animal is in the habit of licking, in order 

 that the larvae may be transported on its tongue into its mouth, where 

 they can proceed to their destined dwelling. Thus, the female (Estrus 

 avis places her eggs on the internal margin of the nostrils of the Sheep, 

 which is no sooner aware of it, than it becomes agitated, strikes the 

 earth with its feet, and flies with its head to the ground. The larvae 

 insinuates itself into the maxilliary and frontal sijiuses, and clings to 

 their lining membrane by means of the two stout hooks with which 

 its mouth is armed. It is thus also that the CEstrus equi deposits 

 her eggs at intervals, without alighting, and by balancing her body 

 in the air, on the inner side of the legs of the Horse, on the side of 

 the shoulders, and rarely on the withers. The CE. hcemorrhoidalis , 

 whose larvae also inhabit the stomach of the same animal, places her 



