CESTRID^. 345 



and devote the whole of their brief existence to the labors 

 of procreation. Only about seventy-five species are 

 known, and they are generally called bot-flies, though 

 the name is frequently applied especially to the bot-fly 

 of the horse. Parasitism occurs in three principal ways: 

 in the stomach and digestive tubes, in tumors formed by 

 the larvae under the skin, and in the pharyngeal and 

 nasal cavities. With but few exceptions each species is 

 confined to a single species of mammal, and each genus 

 or each group of allied species is parasitic in the same 

 way upon allied animals. Seven species of Gastrophilus 

 are found in the stomach and intestines of the horse and 

 ass. Thirteen species of Hypoderma are known to live 

 under the skin of the horse, the ox, the buffalo, the sheep, 

 the goat, four species of antelope, and the musk-deer. 

 Two species of CEstromyia likewise infest the skin of La- 

 gomys and Hypodcsus. CEdamagena tarandi is parasitic in 

 great numbers in the skin of the reindeer in both Siberia 

 and boreal America. Four or five species of CEstrus live 

 in the nasal sinuses of sheep, antelope, and horse (Rhin- 

 czstrus). One species of Cephalomyta lives in the nasal 

 cavities and throat of the camel and buffalo. Six or 

 seven species of Cephenomyia have been found parasitic 

 in the pharyngeal cavities of various Cervids, while va- 

 rious species of Cuterebra, Bogeria and Rogenhofera have 

 been bred from the skin or scrotum of rodents and 

 opossums. Two species of Dermatobia have been obtain- 

 ed from the skin of dogs, cattle, cats, deer, and probably 

 apes and man. The eggs or young larvae are, it is be- 

 lieved, in all cases taken into the mouth by the animals 

 which they infest, going thence to the sinuses, pharynx 

 or stomach; or, through the tissues of the body, to the 

 skin. Perhaps those living within the scrotum may reach 

 their abiding place by a more direct route. 



32 



