92 



S. HADWEN AND A. E. CAMERON. 



The facts regarding the life-history and habits of G. intestinalis are much more 

 extensive than those of G. haemorrhoidalis and G. nasalis, thanks, in great measure, 

 to the excellent and careful work of Osborn (4), who has emphasized the importance 

 of moisture, friction and warmth as factors necessary to the successful hatching of 

 the eggs. His results in this direction have been in the main confirmed by 

 Collinge (6). 



The Egg. 



Gastrophilus intestinalis. 



The stalkless egg is generally laid at the distal end of a hair, in full view. It measures 

 on the average about l - 25 mm. in length and about - 379 mm. at its widest part 

 just posterior to the operculum. General colour, greyish yellow to yellow. General 

 shape navicular, more or less flatly oval in section. Two attaching sub-parallel 

 flanges project on the side proximal to the supporting hair, which they encircle, 

 commencing at a point removed about one- third from the anterior end of the egg and 

 terminating just short of the posterior extremity ; the non-flanged, anterior third 



Pig. 1. Egg of ^Gastrophilus intestinalis, X 50 



makes an angle of about 30 degrees with the supporting hair. Chorion traversed 

 by a close series of very delicate, transverse ; sub-parallel striae continuous with 

 those of the flanges ; some striae interrupted and broken ihtheir course. Operculum 

 non-striate and apparently unsculptured, more or less flat, arising and arching some- 

 what abruptly on the side nearer the hair, imparting a rather truncate appearance 

 to the anterior extremity of the^egg (fig. 1). Chorion closely invested internally 

 by a delicate membrane enclosing the larva (fig. 2). 



Fig. 2. Egg membrane enclosing unmatched larva of 

 Gastrophilus intestinalis, X 70. 



The eggs of G. intestinalis may be found promiscuously on the shoulders of the 

 horse, mane, fore-legs, antero-interno-inferior part of the knee and postero-internal 

 region of the fetlock. The long hairs which invest the inside of the fore-legs would 

 appear to be especially favoured by the adults in ovipositing. The eggs have also 

 been found on the hind-legs, particularly on the inside of the hocks, but here they 

 occur only in small numbers. 



