76 BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE | 
tember. There is then a gradual reduction in numbers until about 
January 1, when all have migrated from the gullet. 
In southwestern Texas the larvee 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., larvee began to appear in the gullet about the 
middle of July and the last larve left that organ about April 1. | 
Thus it is certain that the larve 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 larva 
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 larve of Z. 
lineatum in the backs of cattle occur in the plateau region of 
western Texas. On August 10, 1919, at Roosevelt, 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 larvee 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 
larvee 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 larvee in this case evidently had been present 
about 10 days. 
Mr. Parman’s records at Uvalde indicate that larve usually 
begin to appear under the skin about the middle of September. 
Some years, 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. 3 3 } 
At Dallas, Tex., fairly accurate records of the earliest appearance 
of larve 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 larvee appeared about September 8. 
At Herkimer, N. Y., the date of appearance of larve of H. 
lineatum in the subdermal tissue of the backs of cattle was found 
in 1920 to be about March 1, and in 1922 about February 6. At 
Middletown, N. Y., in 1920 larvee of H. lineatum 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 County, IL, 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 sub- 
