ANIMAL 1'AKASITES AND DISEASES. 6l 



pliilus of the Horse are yellowish-white in colour and conical in shape, 

 being 1.25 mm. long; they are transversely striated, and provided at 

 the larger extremity with an operculum, which is obliquely truncated. 

 They adhere to the hairs by their narrow end, in the same manner as 

 the ' nits ' of the Louse, by means of a viscid matter that is deposited 

 with them; their wide end remains pendent." 



The idea that the eggs were conical at one end and adhered to the 

 hairs of the horse by a sticky secretion seems to have been copied from 

 Bracy Clark's account 1 by practically all succeeding writers. 



Xo mention is made of the egg by Schroeder van der Kolk 2 in his 

 classical account of the anatomy of this insect. 



A carekil examination of the egg at once proves the incorrectness 

 of the above accounts, and it seems strange that when the eggs of 

 other species of Oestridae have been so carefully figured and described, 

 no one should have thought it worth while to carefully examine those 

 of the species under consideration. 



I therefore propose to here give a short description of the egg, 

 together with figures made from recently deposited specimens. 



When deposited the eggs are almost white in colour, afterwards 

 turning to a light yellow or a dirty white. They show a well-marked 

 series of transversely raised ridges situated at about equal distance 

 apart, here and there having a wavy or sinuous character and occa- 

 sionally merging into one another. 



In length they average 1.25 mm. and taper to a blunt point at 

 one end and are obliquely truncate at the other. This the anterior or 

 pendent end is covered by a cap or operculum, which lies obliquely to 

 the long axis of the egg and not at a right angle. 



Like that of Hypoderma the egg may be said to consist of two 

 parts, viz., the egg proper and a pair of lips or valves, which close 

 round the hair and secure the attachment of the egg. The wavy 

 striation is continuous over these lip-like bodies. 



If the egg is detached from the hair the margins of these lips 

 usually adhere to it and a very definite attachment surface can be 

 made out on the egg. (Figs. 30, 31). 



The peripheral margin of the operculum extends slightly over the 



1 Trans. Linn. Sec., 1797, vol. iii. 



i Nieuwe Verhandl. K. NeJerl. Inst., Amsterdam, 1845, T. 9, pp. 1-55, pits, i-xiii. 



