2 BULIETIN 1369, U. 8S. DEPARFMENT OF AGRICULTURE 
tories, habits, injuriousness, and means of repression of cae two 
species, as obtained during this investigation.* 
HISTORY 
The heel flies or warble flies, or at least the effects of their fiacle. 
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 1718 by the Italian 
naturalist Vallisnieri (102, 103)* make very interesting reading. 
Linné (67), 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 2s was believed by all previous writers, and as some so 
sequent writers have believed. 
In 1797 Clark (20) published a notable account for that day of 
the Oestride, including observations on the habits of the cattle 
grubs. This modified and amplified views were published in 1827 
(27) and 1848 (22). 
In 1863 the Austrian entomologist emer (S) published his 
monograph of the Oestride, which added much to the knowledge 
of the species. He describes the last two stages of the larve, and 
in a subsequent article (9) he indicates a simple method of dif- 
ferentiating the last larval stages of H. lineatum and ZH. bovis. 
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 the fact that the cattle are driven to a frenzy by the oviposit- 
ing flies, the conclusion being that the flies must stine when lay- 
ing the evos—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 (4/) on the find- 
ing of Hypoderma larve 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) larve in 
the spinal canal of cattle in December, January, March, May, and 
June. He also concluded, apparently without having seen the ege 
or the fly ovipositing, that the hosts take up the eggs with grass 
and that the young larve reach the spinal cavity from the diges- 
3The 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. During the 
prosecutien of the work the writers have been materially assisted by many individuais 
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 pane 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 Jess associated with the writers in the carrying out of the observa- 
tions and experiments. Whe following men have contributed materially to the results 
as herein given: D. C. Parman, O. G. Babcock, Oscar Pool, E. E. Wehr, H. P. Wood, 
and W. E. Dove. 
4 Numbers in italies refer to ‘‘ Literature cited,” p. 114. 
pak e 
