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BULLETIN- 1369, IT. S. DEPARTMENT OP AGRiCtlLTtJEE 



place among reared specimens. Among a large number of adults '• 

 of H. horns which emerged early in the morning and were kept in i 

 lantern globes, many pairs were observed in copula about 10 a. m. ' 

 as the temperature rose. The duration of the act ranged from two • 

 to two and one-half minutes. I 



OVIPOSITION 



Reference has been made already to an instance of a fly begin- 

 ning oviposition within about an hour of the time she emerged. 

 The writers' observations in the field indicate that if favorable 

 weather conditions prevail oviposition usually begins on the same 



day the adults emerge. It 

 also appears that with flies 

 in the field and with those 

 captured and placed on ex- 

 perimental animals the ma- 

 jority of the eggs deposited 

 by an individual are laid 

 during a single day. In 

 several instances flies de- 

 posited a large number of 

 eggs during one day and a 

 moderate number during 

 the second day, but in no 

 case have specimens ovi- 

 posited during three suc- 

 cessive days. 



As has been pointed out 

 by Hadwen and other au- 

 thors, the methods of ovi- 

 position are very different 

 in H. lineatum and H. 

 hovis. The former attacks 

 more stealthily than the 

 latter, and several eggs are 

 usually placed on a single 

 hair, while with H. hovis 

 the eggs are laid singly. 

 This difference in the action 

 of the flies during their oviposition is intimately associated with the 

 fright produced among cattle, as will be discussed later. 



In the field when cattle come in the vicinity of a resting female 

 of H. lineatum the insect is observed to approach them on the wing, 

 usually alighting on the ground close to an animal and frequently 

 approaching the hind legs of the host by a series of short flights 

 wliich resemble jumps. She sometimes lights directly on the heel, 

 usually below the dewclaws, and immediately begins to extend the 

 ovipositor, grasping the hair and cementing on her eggs (fig. 32). 

 In other instances if the animal is not moving she may come close 

 to the heel of the host, turn around, and back up to the rear of 

 the hoof with the ovipositor extended. In this way the short hairs 

 between the hoofs are reached and the eggs are placed in position 



Fig. 32. 



-Heel fly (Hypoderma lineatum) oviposit- 

 ing upon leg of cow 



