204 (ESTRID.E, OR BOT-FLIES. 



733. The OEsiRiD^E, or Bot-flies, are a family very remark- 

 able in regard to their structure and habits. The perfect insects 

 resemble large Meat-flies in form, are very hairy, and have these 

 hairs coloured in rings, like Humble Bees ; but they are seldom 

 seen, the duration of their lives being very short in this condition. 

 Their chief peculiarity consists in the 

 absence of any proper mouth in the 

 Imago (in which respect there is an 

 analogy with the Strepsiptera, 714), 

 and in the peculiar habitation of the 

 Larva. This is always found in 

 living animals, its situation, how- 

 FIO. 430.-CESTRUS AND LARVA. Q ^^ varying with the species; and 

 almost every herbivorous animal having one or more peculiar 

 to it. The egg is, in some cases, deposited by the parent in 

 situations where the larva may burrow into the flesh ; there 

 it occasions inflammatory tumors, the fluids contained in which 

 afford it nourishment. These have an evident analogy, there- 

 fore, to the Cynipidae, which produce Vegetable galls. In other 

 instances, the eggs or larvas, existing upon spots which the animal 

 is in the habit of licking, are conveyed by the tongue into the 

 mouth, whence they pass into the stomach. There they remain 

 until full-grown ; and then they quit the body (as do also those 

 which inhabit the flesh), and fall to the ground, beneath the sur- 

 face of which they undergo their transformations. The larvae 

 of one species, which inhabits the Sheep, are found in the frontal 

 sinuses of the skull. Man is subject to the attacks of one or 

 more species ; which do not, however, inhabit this country. 



