SI 5 



ANNUAL REGISTER, 1805. 



" in the stomach are very various, 

 " often not more than half a dozen, 

 " at other times more than a hun- 

 " dred, and if sonie accounts might 

 " be relied on, even a much greater 

 *' number than this. They hang 

 *' most commonly in clusters, being 

 " fixed by the small end to the inner 

 *' membrane of the stomach, which 

 *' they adhere to by means of two 

 *' small hooks or tentacula. When 

 *' they arc removed from the stomach 

 *' they will attacli themselves to any 

 " loose membrane, and even to the 

 *■<■ skin of the hand." 



" The body of the larva is com- 

 <' posed of eleven segments, all of 

 *' which, except the two last, are 

 *' surrounded with a double row of 

 *' horny bristles, directed towards 

 *' the truncated end, and are of a 

 <' reddish colour, except the points, 

 " which are black. These larvde 

 *' evidently receive their food at the 

 " small end, by a longitudinal ap- 

 *' perture, which is situated between 

 *' two hooks or tentacula. Their 

 ^' food is probably the chyle, which, 

 *' being nearly pure aliment, may 

 " go wholly to the composition of 

 " their bodies without any excre- 

 " mentitious residue, tliough on dis- 

 *' section the intestine is found to 

 " contain a yellow or greenish niat- 

 " ter, which is derived from theco- 

 " lour of the food, and shews that 

 *' the chyle, as they receive it, is not 

 *' perfectly pure." 



" They attain their full growth 



♦ ' about the latter end of Way, and 

 <' are coming from the horse from 

 ♦' this time to the latter end of June, 

 i- or sometimes later. On dropping 

 <' to the ground, they find out some 



♦ ' convenient retreat, and change to 

 *' the chrysalis; and in about six or 

 *' seven weeks the lly appears." 



To the above account by Mr. 



Clark I have only to add, that the 

 most successful method of obtaining 

 the liics- from the chrysalis is by 

 taking the larva;, when fresh drop- 

 ped from the horse, and immediately 

 enclosing them separately in balls 

 of fresh horse-dung, which must be 

 kept in a warm situation, and 

 sprinkled every second or third day 

 with water: the animals will thu5 

 be preserved in a proper degree of 

 warmth and moisture, and the flies 

 will make their appearance in tho 

 usual time. 



Oestrus ovis, or the sheep gad 

 fly, is so named from its larva 

 inhabiting the nostrils and frontal 

 sinuses of sheep in particular, 

 though it is also found in similar 

 situations in deer and some other 

 quadrupeds. Jt is a smaller species 

 than either of the two precediug, 

 and is of a whitisii grey colour, 

 with the thorax marked by four lon- 

 gitudinal black streaks, and the ab- 

 domen speckled with black. The 

 larvae are nearly as large as those of 

 the oestrus equi, and, according to 

 the observations of Mr. Clark, are 

 of a delicate white colour, flat on 

 the under-side, and convex on the 

 upper ; having no spines at the di- 

 visions of the segments, though they 

 are provided with tentacula at the 

 small end. The other is truncated, 

 with a prominent ring or margin. 

 When young, these larva; arc per- 

 fectly white and transparent, but as 

 they increase in size, the upper side 

 becomes marked with two transverse 

 brown lines on each segment, and 

 some spots are seen on the sides. 

 They move with considerable quick- 

 ness ; holding with their tentacula] 

 as a fixed point, and drawing upi 

 the body towards them. Mr. Clark, I 

 in his description of this species, ob-j 

 serves that he has mostly found the! 



larvas 



ik 



