GADFLIES AND BOTFLIES 



3035 



like $40,000,000 per annum is sustained. The mischief begins in the summer, 

 when the cattle gallop about in terror in their vain efforts to escape the 

 flies seeking to deposit their eggs upon them. This causes waste of milk and 

 damage to health. Then there is the damage to the meat by the destruction of 

 the tissue just under the hide, resulting in what butchers call licked meat or jelly. 

 And lastly, there is the evidence of tanners as to the damage to hides; one estimate 

 given by a firm putting the loss on hides sold at two markets in Birmingham during 

 seven weeks at $2,700; while a Nottingham authority reckons the loss in that town 

 at $7,500 to $10,000 per annum. The sheep botfly (CEstrus ovis} lays its eggs in 

 the nostrils of sheep, and the maggots after being hatched pass up the nasal pas- 

 sages and enter the chamber in the bones of the forehead, where they nourish them- 

 selves on the mucus to which the irritation of their presence gives rise. The 

 presence of these parasites, which are seldom fewer than seven or eight at a time, is 

 most injurious to the infested animal, and gives rise to a sickness of a very serious 

 nature. At the end of about nine months the larvae reach maturity, and making 

 their way again into the nostrils are expelled by the sneezing of their host, and 

 reaching the ground bury themselves, and remain concealed until they emerge as 

 perfect insects from the pupal stage. The three species above mentioned serve as 

 types of the life histories of the entire family, which contains in addition a large 

 number of genera and species infesting various kinds of animals. Even man him- 

 self is not exempt from their attacks, and all kinds of domestic cattle and beasts of 

 burden, such as reindeer, camels, and elephants, are liable to be infested with them. 

 Two notices of the occurrence of 

 larvae in human beings were pub- 

 lished by John Howship in 1833. 

 In both cases the larvae, named 

 Oestrus humanus, were extracted 

 from tumors, the sufferer in one 

 case being a soldier in Surinam, 

 and in the other a carpenter in 

 Columbia. In addition to the 

 mammals mentioned, others, 

 such as hares, rabbits, mice, and 

 voles, often suffer from these 

 parasites. Their larvae have 

 also been met with in birds and 

 frogs. Schneider, for instance, 

 states that two larvae much re- 

 sembling those of Hypoderma 

 were obtained from under the 



skin of the head of a young sparrow, where they had produced two large hard 

 tumors, and Krefft has given descriptions of specimens belonging to the genus 

 Batrachomyia that were found living parasitically upon Australian frogs. The larvae 

 were situated between the skin and the flesh behind the drum of the ear, and could 

 be squeezed out through apertures in the skin. 



LIFE HISTORY OF SHEEP BOTFLY. 



a. Adult fly; b. Larva from upper side; c. Pupa from under 

 side. (All enlarged.) 



