A CONTRIBUTION TO THE KNOWLEDGE OE BOT-FLIES. 93 



In a paper by M. J. Rodham (13), to which our attention was drawn by M. J. 

 Bequaert, of the American Museum of Natural History, New York, the author 

 records the finding of the eggs of the Oestrid of the rhinoceros (Gyrostigma), which 

 were submitted to him from the Belgian Congo. In his description he says that the 

 general form of the egg recalls that of Gastrophilus intestinalis by reason of the delicate 

 and regular transverse striation of its walls, as well as by the oblique attachment 

 of the apical operculum. It differs, however, from the egg of G. intestinalis in that 

 it is devoid of flanges, their function being assumed by a posterior falciform appendage 

 applied to the skin of the host. It is further suggested that the hatching of the 

 eggs is effected in a manner similar to that which occurs in the case of 

 G. intestinalis, namely, one animal licking another. 



Gastrophilus nasalis. 



Egg stalkless, generally laid at the proximal end of the hair near the'skin, obscured 

 externally among the overlapping hairs. Average length about 1 -25 mm. Average 

 breadth at widest part, midway between the two extremities, about 0-339 mm. 

 G-eneral colour, whitish yellow. General shape elongate ovate, sub-circular in 

 section. The two attaching sub-parallel flanges commence just posterior to the 

 anterior extremity and run almost the entire length of the egg, stopping just short 

 of the posterior extremity. The long axis of the egg almost parallel to that of the 

 supporting hair. Chorion traversed by a close series of very delicate, transverse, 



Pig. 3. Egg of Gastrophilus nasalis, X 50. 



sub-parallel striae, continued on the flanges ; some striae interrupted and broken 

 in their course. Operculum non-striate and non-reticulate, dome-shaped, its 

 horizontal axis at right angles with the longitudinal axis of the egg, terminally placed 

 on the anterior end (fig. 3). Chorion with internal investing membrane enveloping 

 the unhatched larva. 



The eggs are generally laid on the hairs of the intermaxillary space between the 

 rami of the mandibles beneath the head. Theobald (6) and other authors are of the 

 impression that the species deposits its eggs in the nasal orifices, but in our 

 experience, this is contrary to fact. 



Gastrophilus haemorrJioidalis. 



Egg stalked, the stalk a continuation of the broad chorionic flanges, hollow and 

 open all along one side for the reception of the supporting hair. Average length 

 1'5 mm. Average breadth at widest part near the centre, 0'345 mm. General 

 colour brownish black. General shape somewhat barnacle-like and compressed, 

 flatly ellipsoidal in section. The two attaching sub-parallel flanges commence at 

 a point removed about one-third from the anterior extremity of the egg, are continued 

 into the stalk, which is about two-thirds the length of the egg, and taper off somewhat 



(C478) a2 



