﻿THE CATTLE GRUBS OR OX WARBLES 



59 



spiracle to the hole and almost perpendicular to it. Thus the hole 

 in the skin is always near the posterior end of the larva, which may 

 have the anterior portion in any direction. The majority of the 

 cysts have the aperture near the upper side. 



TOTAL DEVELOPMENTAL PERIOD IN THE BACKS OF CATTLE 



As with other stages of Hypoderma, there is a variation in the 

 total period required for the development of the larvae from the time 

 the holes are cut through until the larval growth is completed. The 

 determination of this period with accuracy is of much importance 

 in control and especially in eradication work, since the interval 

 between treatments 

 should be governed 

 by such data. 



In a large num- 

 ber of cattle of sev- 

 eral breeds warbles 

 of both species were 

 followed through 

 their entire develop- 

 ment in the subder- 

 mal tissue. Owing 

 to the high mor- 

 tality among the 

 larvse, especially 

 when examined re- 

 peatedly to deter- 

 mine molts, etc., 

 only a comparative- 

 ly few records of 

 complete develop- 

 ment were obtained 

 among the hundreds 

 of warbles observed. 



In order that the 

 duration of the lar- 

 val stages might be 

 determined various 

 individual cattle 

 were observed from 

 the time warbles began to appear until all grubs had made a normal 

 egress. These observations were made as froqiiently as time would 

 permit, usually once each day. Through practice the touch was 

 developed to a high degree and one could readily detect the first 

 indication of a foreign object undei- the skin or a minute amount of 

 exudate fi-om a puncture of the skin. 



Ill making the examinations a headlight was developed which 

 proved of great value (fig. 2H). It consisted of a sliortcned (hish 

 light attached to a head band, and sei-ved b^y t^vo (h-y cells nwvw.d 

 on a belt. The focus was adjusted to jjennit the observer to use a 

 hand lens. 



With the younger stages of the laivie m ijarticuhir it was lound 

 necessary to" apply pressure around tliem to force (iiem toward the 



Headlight outfit used in examining cattle grubs 

 in cysts 



