SKIN DISEASES CA USED BY INSECTS. 



687 



the horse, an affection of the skin which is localized upon certain 

 regions, and due to numerous round worms situated between the 

 epidermis and derma. 



SKIN DISEASES CAUSED BY INSECTS. 



Some insects annoy the animals of our different species without 

 producing any true morbid process in the integument. During 

 the warm season they torment and irritate the animals constantly 

 during meals and are the cause of wasting part of the food ; among 

 them we must mention the common fly (Musca domestica) and the 

 corvina fly {Musca corvina), which suck the perspiration. Others 

 — the gadfly of the ox (Tabanus bovinus), the small rain breeze 

 fly (Hœmatopota ; T. pluvialls), the little blinding gadfly [T. 

 cœcutiens), etc. — suck the blood, especially in regions where the 

 skin is thin. Others again — the common gnat (Culex pipiens), the 

 stingiug stomox (Stomoxys cahitrans), the meteoric anthomyia 

 (Anthomyia or Hydrotœa meteorica, the creeping simulium {Simu- 

 lium reptens), and the most dangerous of all, Kolumbacz's simulium 

 {8. Columbaczensis) — throw themselves upon the animals and make 

 a great many bites in the skin, which are followed by a more or 

 less intense dermatitis. The larvae of some live in the integu- 

 mentary membrane : the calliphora, or blue meat-fly {Musca vom- 

 itoria), the carnivorous sarcophagus {Sarcophaga carnaria), the 

 cadaver fly (Musca cadaverina), which deposit their eggs in wounds 

 and ulcerations, finally the hypoderma of the ox (Œstrus bovis), 

 the larvse of which perforate the skin in order to penetrate as far 

 as the subcutaneous connective tissue. 



Amono; these insects those which offer the most interest from a 

 pathological standpoint are : 



1. Simulium of Kolumbacz, or spotted simulium, which is 

 of ash-gray color, and about the size of a flea. It was first ob- 

 served in the neighborhood of Kolumbacz, Hungary (Banat of 

 Temesvar) ; in 1783 it produced the death of nearly six hundred 

 animals (horses, oxen, pigs, sheep) in this region. It is found in 

 Austria, Bohemia, Prussia, and several German provinces. After 

 freshets immense swarms of these flies are often seen ; they come 

 in actual clouds, which fall upon the animals and literally cover 

 them with a blackish mantle, penetrating into the natural orifices 

 (mouth, nose, ears and eyes, vagina and rectum), and covering the 



