28 HISTORY OF INSECTS. 



downward (page 25, figs, a, h), and is thus well disposed for 

 the operation of the tongue in removing the operculum, 

 which is of an oval figure, and surrounded with a pro- 

 minent margin. The microscope shows the case of the egg 

 to be shagreened in squares, or impressed longitudinally 

 and transversely with delicate striae. When the larva 

 or grub is hatched from the egg it is a small active 

 worm, long in proportion to its thickness ; but as its growth 

 advances it becomes proportionably thicker and broader, 

 and beset with bristles. These larvae are very frequent in 

 horses that have been at grass, and are in general found 

 adhering to the white insensible tissue or coat which comes 

 from the lining of the oesophagus, and extends over the 

 upper part of the stomach. They make small, deep, 

 round holes wherever they adhere to this white tissue, and 

 sometimes so deep as to pass through it, but not tlii'ough 

 the other layers or coats of the stomach. 



The larvae usually hang in dense clusters from the lining 

 of the stomach, and maintain their hold by means of two 

 dark brown hooks; between these a longitudinal slit or 

 fissure is seen, which is the mouth of the larva. When 

 the larvae are removed from the stomach with a sudden 

 jerk so as not to injure them, they will, if fresh and healthy, 

 attach themselves to any flaccid membrane, and even 

 to the skin of the hand. For this purpose they sheath or 

 draw back the hooks almost entirely within the skin, till 

 the two points come close to each other ; they then present 

 them to the membrane, and keeping them parallel till it is 

 pierced through, they expand them in a lateral direction, 

 and afterwards, by bringing the points downwards towards 

 themselves, they include a sufficient piece of the mem- 

 brane to enable them to remain firmly fixed for any length 

 of time as at anchor, without requiring any further exertion. 

 The body of the larva is of a whitish red colour, and ap- 



