Carpenter & Hewitt — Genitalia and Larva of the Warble-fly. 279 



with hex* abdomen flat on the ground, the ovipositor somewhat protruded, 

 After pairing the female remains quiescent for a while, gently moving tlie 

 ovipositor in and out. 



The First-stage Larva. 



1. Its Mode of Hatching. 



Tlie eggs of Hypoderma have been repeatedly described and figured, and it 

 lias for many years past been well known that they are attached to the hairs of 

 the cattle by means of the grooved flange-like outgrowth from the hinder pole 

 of the Ggg (Plate XXVI, fig. 37). Describing the egg-laying habits of Sijpo- 

 derma linealum in North America, Curtice ('91) and Eiley ('92) stated that a 

 number of eggs were attached in a row to a single hair. Hadwen ('12) has 

 recently observed the egg-layiug of H. bovis in British Columbia (we believe 

 that this species had not befoi'e been certainly recorded from America), and he 

 states that the eggs are always laid singly close to the base of the hair, 

 expressing some doubt as to the correctness of Curtice and Riley's description 

 and drawing. We can confirm Hadwen's statement with regard to H. bovis from 

 our own observations at Ballyhaise last year; and the position of the eggs, close 

 to the beast's skin, so that in order to see them the overlying hairs must be 

 carefully removed, is doubtless the chief reason why they have been so rarely 

 noticed on the living animal. Glaser, however, who is working at the problem 

 of the Warble-flies' life-histoi'y in Germany, has just published ('13) some 

 highly interesting results, and confirms Curtice and Kiley's account with regard 

 to II. lineatum, whose female clings to the calf or cow better than H. bovis does, 

 and is able to lay several eggs in series on one hair, while hovis lays only one 

 egg at a time. This difference in habit between the two species in the mode 

 of egg-laying is remarkable. We can fully confirm G-laser's statement that 

 H. bovis, like H. lineatum, lays her eggs chiefly on the hind limbs, just below 

 the heel-joint or hock. Eggs are rarely laid on the belly, flanks, or breast, 

 and never, under natural conditions, on the back. A female fly " sleeved " on 

 the back of a calf will, however, lay eggs there; and it proves a more 

 convenient place for examination than the heel. We have also induced a 

 captive female H. bovis to lay eggs on a calf's hairs in a glass tube. Glaser 

 held some cut-off hairs behind a lineatum female's abdomen ; she laid eggs on 

 them, and he placed the hairs on earth in a flower-pot, where they hatched in 

 twelve days ; eggs laid by the same female on Glaser's trousers hatched in 

 eight days, accelerated by the body-heat. Eggs of H. bovis which he observed 

 laid on a calf showed segmentation of the embryo in twenty-flve hours, and 

 hatched in three and a half days. We kept eggs of H. bovis in an incubator 



