﻿76 BULLETIN 1369, U. S, DEPARTMENT OF AGEICULTURE 



tember. There is then a gradual reduction in numbers until about 

 January 1, when all have migrated from, the gullet. 



In southwestern Texas the larvse begin to reach the gullets dis- 

 tinctly earlier than at Dallas, thus closely conforming with the 

 earlier appearance of adults in that region. The earliest larva ob- 

 served by the writers to appear in a gullet was a single specimen 4.2 

 millimeters in length taken from an animal slaughtered in a Fort 

 Worth, Tex., packing house on January 4, 1924. This specimen evi- 

 dently developed from eggs deposited the previous fall. 



At Herkimer, N. Y., larvae began to appear in the gullet about the 

 middle of July and the last larvae left that organ about April 1. 

 Thus it is certain that the larvas are to be found in the gullets for 

 about nine months. 



The seasonal prevalence of larvee in the subcutaneous tissues of 

 the backs of cattle is closely correlated with the time when the larvae 

 reach the maximum size attained by them in the gullet, and to some 

 extent with the period of adult activity. Knowledge of this subject 

 is of vital importance in connection with any control procedure, yet 

 the information published is meager in the extreme. 



The earliest appearances in the United States of larvae of K. 

 lineatwm in the backs of cattle occur in the plateau region of 

 western Texas. On August 10, 1919, at Koosevelt, Tex., O. G. 

 Babcock observed grubs in considerable numbers in the backs of 

 cattle. A few collected on August 12 showed some to be in the 

 early fifth stage. Thus they must have appeared on the backs 

 about July 15. In 1923 fifth-stage larvae were found by Mr. Babcock 

 at Sonora, Tex., on August 22. These must have reached the backs 

 of the cattle about July 30. At Uvalde, Tex., records made by 

 D. C. Parman during several years show that the first appearance of 

 larvae in the backs of cattle is later than it is in the plateau region 

 to the north. The earliest appearance noted at Uvalde was on 

 August 12, 1918. The larvae in this case evidently had been present 

 about 10 days. 



Mr. Barman's records at Uvalde indicate that larvae usually 

 begin to appear under the skin about the middle of September. 

 Some 3^ears, however, they may appear as late as October 9, as 

 was observed in 1920. During that season the maximum number 

 present was noted on January 15. 



At Dallas, Tex., fairly accurate records of the earliest appearance 

 of larvae in the subdermal tissue have been made in 10 different 

 years, during the period from 1907 to 1922. These dates have 

 been rather uniform, ranging from about October 10 in 1914 and 

 1918 to October 30 in 1916. The year 1923 was an exception, as 

 in that year the larvae appeared about September 8. 



At Herkimer, N". Y., the date of appearance of larvae of H. 

 Uneafum in the subdermal tissue of the backs of cattle was found 

 in 1920 to be about March I, and in 1922 about February 6. At 

 Middletown, N. Y., in 1920 larvae of H. Uneatum came to the backs 

 about February 12, and in 1923 about February 1. At Watertown, 

 N. Y., in 1920 the date of earliest appearance was about March 3. 

 In Kane Countv, HI., C. C. Compton found a single small larva in 

 one of 200 cattle examined on February 7, 1924, thus showing the 

 earliest appearance to be soon after February 1. Subsequent col- 

 lections made by Mr. Compton indicate that this date is svib- 



