152 INDIRECT INJURIES CAUSED BY INSECTS. 



by the auger just described, always continues open, and 

 increases in diameter as the larva .increases in size ; 

 thus enabling- it to receive a sufficient supply of air by 

 means of its anal respiratory plates, which are usually 

 near the orifice. — But though these insects thus torment 

 and terrify our cattle, they do them no material injury. 

 Indeed they occasion considerable tumours under the 

 skin, where the bots reside, .varying in number from 

 three or four to thirty or forty ; but these seem unat- 

 tended by any pain, and are so far from being injurious, 

 that they are rather regarded as proofs of the good- 

 ness of the animal, since these flies only attack young 

 and healthy subjects. The tanners also prefer those 

 hides that have the greatest number of bot-holes in 

 them, which are always the best and strongest^. 



The Stomoxys, and several of the other flies before 

 enumerated, as well as the dog and American ticks, 

 are as prejudicial to the ox as to the horse. One spe- 

 cies of Hippobosca I have reason to believe is appro- 

 priated to them : yet, since a single specimen only has 

 hitherto been taken ^, little can be said with respeCt to 

 it. — A worse pest than any hitherto enumerated, is a 

 minute fly concerning the genus of which there is some 

 doubt, Fabricius considering it as aRhagio, (i?. cohan- 

 baschensis,) and Latreille as a Simulium''. Perhaps 



* Much of the information here collected is taken from Rea-jm. iv. 

 3Iem. 12; and Clark in Linn. Trans, iii. i^S9. 



'' The writer of the present letter is poisesspr of this specimen, which 

 he took on himself in a field where oxen were feeding. Plate V. Fig, 1, 



'^ In the Systema Antliutonan (p. 56) Fahiicius most strangely con- 

 giders this insect as synonymous with Cule.v reptans, L. calling it Scalopse 

 reptans, and dropping his former reference to Pallas, and account of its 

 injurious properties. 



