﻿THE CATTLE GRUBS OR OX WARBLES 3 



the tract, thence migrating up to the subcutaneous tissues of the 

 back. In 1889 one of these early-stage larvae found in the brain of 

 a horse by Poulson was described by Boas (5) as a first-stage Hj- 

 poderma larva. From this time on the veterinarians, especially 

 of Denmark and Germany, made important contributions regard- 

 ing the young stages within the bodies of cattle. 



During the decade beginning in 1884, the English entomologist 

 Ormerod made a number of contributions to the literature of this 

 subject culminating in reports published in 1894 (71) and 19(30 (72). 

 In these articles much valuable information is presented, especially 

 as regards losses. This writer entertained the old idea that the 

 larvae penetrate through the skin of the backs of the cattle. 



In America, interest in this pest began to be evident during the 

 eighties; and articles were contributed by Riley {82, 83) in 1889. 

 In 1890 Cooper Curtice published a note {2Jf) reporting the finding 

 of larvae 10 to 15 millimeters long in the; Myalls of the esophagus, in 

 the pleura near the eleventh rib, in the subcutaneous tissues of the 

 back, and in subcutaneous tumors which opened through the external 

 skin. He states that the finding of larvae in the early stages in these 

 situations suggests that — 



It is possible that the eggs or young larvfe are licl^ed by the cattle from the 

 back ; that the larvse made their way into the esophageal walls and from 

 thence, during the proper season, through the back in the neighborhood of the 

 eleventh rib, to the skin. 



Curtice gives in 1891 {25) a full account of his work along this 

 line. This hypothesis was based upon the finding of these immature 

 stages in the submucous membranes of the gullet and in other tissues 

 of the body, often months before the larvae appeared on the back and 

 cut holes through the skin. He also observed that the larvae and 

 inflammation disappeared from the gullet by the end of January or 

 earl}'^ in February. Apparently no observations Avere made on the 

 actual habit of oviposition of the flies. In 1892 Riley (<f.^) published 

 a very good resume of the knowledge of the life history and habits 

 of FI. lirteatnm up to that date. He concluded from an examination 

 of material from various sources that H. Iineatu7n was the predomi- 

 nant if not the only species found in the United States, In this 

 article he also incorporated an account, based on observations of 

 G. Schaupp and others, regarding the actual method of oviposition 

 of this species, and the true first stage was described for the. first 

 time. He accepts Curtice's theory of the entrance via the mouth, 

 and concludes that an additional link in the chain of circumstantial 

 evidence pointing toward this method of ingress is supplied by the 

 fact that the eggs are laid largely on the legs and that the cattle lick 

 themselves in that region. In 1897 Marlatt {dJf) presented a concise 

 summary of the information available at that time. 



Home, working largely on the immature stages within the bodies 

 of cattle, jjublished in Norway in 1894 {.!/)) observations showing 

 that the larvte are truly migr.itory. He observed them in various 

 situations, including the spinal column from one end to the other, 

 sometimes under the pleura, in the abdominal cavity, and on the 

 surface of the kidney. The following year the veterinarian Ruser 

 {80) published his observations on the occurrence of the larvae in 

 the spinal canal and repoited that he had found traces of larval 

 tracks, in tlie muscles of the back. In 1898 Koorevaar (5-0? working 



