﻿72 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. lineatwny deposits its eggs in series 

 on the same hair, the rate of egg laying is somewhat faster than with 

 H. hovis. 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. hcyvis, is very 

 difficult to determine. The maximum number obseiTcd 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. lineatuon 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 w^hen 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 H. 

 hovis and H. Uneatu^n 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 T 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 H. 

 hovis will oviposit is narrower than in H. lineafuTn, although, in 

 localities where both species occur, females of H. hovis 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. 



