; 
ie BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE =| 
in cages containing calves. But in no case were any eggs deposited — 
normally, 
On account of the fact that H. lineatum deposits its eggs in series 
on the same hair, the rate of egg laying is somewhat faster than with 
H. bovis. In some instances the eggs of H. lineatum have been 
seen to be deposited at the rate of nearly 2 per second, and 30 or 40 
may be deposited in a minute. 
NUMBER OF EGGS DEPOSITED 
The number of eggs deposited, especially by H. bovis, is very 
difficult to determine. The maximum number observed by the writ- — 
ers for H. lineatum was 446. These were deposited by a female 
taken in the act of ovipositing on a cow in a pasture, and hence this 
fly may have laid many eggs before capture. Glaser (29) has ob- 
served a female H. lineatum to deposit 538 eggs, and estimates the © 
total number deposited by this female as 550. In many instances © 
from 200 to 300 eggs have been obtained from a female caught in 
the field in the act of oviposition. Females dissected after they 
have become too weak to deposit) more eggs usually have a good 
number of ova left in the abdomen, although many of these appear 
to be only partially developed. 
CONDITIONS UNDER WHICH OVIPOSITION TAKES PLACE 
Both species of Hypoderma are stimulated to oviposition by 
bright sunlight and usually egg laying takes place largely in the 
sunshine. Both species have been observed, however, to deposit 
eggs in the shade, and occasionally when the sun was fairly well 
covered with clouds, especially if there were occasional bursts of 
sunshine. Oviposition rarely takes place when the sky is heavily 
clouded, and dense shade such as under large sheds appears to be 
shunned by the females of both species. Females of both JZ. 
bovis and H. lineatum have been observed to be active on days 
when the temperatures were comparatively low, provided the sun 
was shining brightly. No doubt in their protected places close 
to the ground reflected heat and sunshine stimulate them to activity 
when the general temperatures are very low. In one instance ovi- 
position of H. lineatum was observed when the temperature was be- 
tween 40 and 45° F. The minimum temperature at 7 o’clock that 
morning was 20.5° F. and the maximum for the day 46° F. at 3 p. m. 
It is difficult to say just what is the optimum temperature, as large 
numbers of flies have been observed ovipositing under a wide range 
of temperature conditions. Females of this species oviposit freely — 
when the temperatures range between 55 and 85° F. provided the 
sun is shining. 
Apparently the range of temperature in which females of 4. 
bovis will oviposit 1s narrower than in ZH. lineatum, although, in 
localities where both species occur, females of H. bovis usually expe- 
rience higher temperature, since they emerge later in the season. 
High winds and even fresh breezes tend to check egg laying of 
both species. Occasionally, however, the flies will oviposit on windy — 
days when the cattle are standing in the sunshine in protected places. 
