﻿2 BULLETIN 136&, U. S. DEPARTMENT OF AGEICtTLTUEfi 



tories, habits, injiiriousness, and means of repression of these two 

 species, as obtained during this investigation." 



HISTORY 



The heel flies or warble flies, or at least the effects of their attacks, 

 have been known to man from time immemorial. The writings of 

 Virgil and Shakespeare contain statements which undoubtedly refer 

 to these pests. Their peculiar and injurious habits have attracted 

 the attention of many naturalists, zoologists, and veterinarians, and 

 the results of the observations and deductions beginning with the 

 articles on this subject published in 1710' and 1713 by the Italian 

 naturalist Vallisnieri {102^ 103Y make very interesting reading. 

 Linne {61)^ in 1739, published information on the related reindeer 

 bot {Oedemagena tarandi L.) and expressed his opinion that the 

 eggs were attached to the skin or hairs and were not pushed through 

 the skin as was believed by all previous writers, and as some sub- 

 sequent writers have believed. 



In 1797 Clark {20) published a notable account for that day of 

 the OestridsB, including observations on the habits of the cattle 

 grubs. Ilis modified and amplified views were published in 1827 

 {21) and 1843 {22). 



In 1863 the Austrian entomologist Brauer {8) published his 

 monograph of the Oestridse, which added much to the knowledge 

 of the species. He describes the last two stages of the larvse, and 

 in a subsequent article {9) he indicates a simple method of dif- 

 ferentiating the last larval stages of H. Jineatum and H. hovis. 



Most writers up to the time of Clark's observations, and in fact 

 many subsequent writers, were of the opinion that the flies place 

 their eggs under the skin of the host. This idea probably originated 

 from tlie fact that the cattle are driven to a frenzy by the oviposit- 

 ing flies, the conclusion being that the flies must sting when lay- 

 ing the eggs — this, despite Linnaeus's statement in 1739 regarding 

 the placement of the reindeer bot eggs on the hairs. 



Up to the publication in 1888 by Hinrichsen {41) on the find- 

 ing of Hypoderma larvse in the spinal canal, only the subdermal 

 or last larval stages were known. Hinrichsen reported the com- 

 mon occurrence of these (now known to be third-stage) larvse in 

 the spinal canal of cattle in December, January, March, May, and 

 June. He also concluded, apparently without having seen the egg 

 or the fly ovipositing, that the hosts take up the eggs with grass 

 and that the young larvse reach the spinal cavity from the diges- 



^ The present studies have been carried on incidental to other projects for a number of 

 years and during the last seven years have received major consideration. Durino- the 

 prosecution of the work the writers have been materially assisted by many individuals 

 and organizations, to whom thanks are extended. The Bureau of Animal Industry, 

 through its various agents, has aided by sending immature stages. Dairymen, especially 

 in the vicinity of Dallas, Tex., and Herkimer and Middletown. N. Y., have assisted 

 materially by permitting the use of their cattle in the writers' experiments. Many 

 specimens and much information have been obtained from correspondents, including 

 dairymen, cattle raisers, hide dealers, butchers, packers, and others interested in the 

 problem. The management of the leading packing plants in Dallas and Fort Worth, 

 Tex., have been especially courteous in furnishing material for examination and in per- 

 mitting examination of cattle during slaughter. Of necessity, a number of entomologists 

 have been more or less associated with the writers in the carrying out of the observa- 

 tions and experiments. The folIo^vlng men have contributed materially to the results 

 as herein given : D. C. Tarman, O. G. Babcock, Oscar Pool, E. E. Wehr, H. P. Wood, 

 and W. E. Dove. 



* Numbers in italics refer to "Literature cited," p. 114. 



