called Oisfros hi/ the Ancients. 409 



same time ; and that the egg being hatched, the young grub 

 insinuates itself into, and finally through the skin, forming an 

 abscess beneath it. In a somewhat similar manner it is that the 

 ichneumon flies deposit their eggs on the sides of living cater- 

 pillars of the Lepidoptera, and hatching, perforate their skins, 

 and entering within, live on the parenchyma or pulp of their 

 bodies till matured and fully grown, when they make their way 

 out again and change to the chrysalis. 



I may also remark of the Œstri, that they appear to be won- 

 derfully kept from such an increase as would be fatal to the 

 animals they feed upon, by the difiicvdties and imminent hazards 

 they are exposed to in the act of depositing their eggs. The 

 teeth of the horse must destroy, one should imagine, nine-tenths 

 of the Œ. Equi, lucmorrhoidalis, and saint /ferns. The Œstri seem 

 how ever, in the hands of Providence, to make a double recom- 

 pense for the sufferings they occasion ; first, by keeping the 

 animals on the alert during hot weather, when they would be 

 often too idly disposed for their welfare ; while the few larvae 

 which succeed in getting into their bodies, appear to benefit 

 them by their local irritations, stimulating tlie stomach to a 

 quicker digestion of their watery food, and diverting diseases by 

 their counter irritations of the skin and frontal cavities, — thus 

 producing the effect of issues or vesicatories, which are powerful 

 remedies in relieving and in preventing diseases. 



I apprehend that I have now sufficiently shown that the 

 Œstrns of the ancients could have been no Tabanns, and that 

 it is clear Olivier, who appears to have originated this notion, 

 and who was followed by Latieille, was mistaken. 



A very extensive enumeration of this genus is seen in a late 

 ingenious publication, the Systematische Beschreibnng of J. W. 

 Meigen. It is however in some instances not correct ; for on 

 carefully examining the Œstrus lineatus of this writer, intro- 



3 G 2 duced 



