INDIRECT INJURIES CAUSED BY INSECTS. 79 



so covered by them, that he could not introduce the point of a knife 

 between them. They were deeply buried in the flesh ; and in one in- 

 stance that he witnessed, the miserable creature was so exhausted by 

 continual suction, that it fell, and afterwards died in great agonies. 1 



No quadruped is more infested by the gad- or bot-fly, sometimes also 

 improperly called the breese 3 , than the horse. In this country no fewer 

 than three species attack it. The most common sort, known by the name 

 of the horse-bee (CEstnis Equi\ deposits its eggs (which being covered 

 with a slimy substance adhere to the hairs) on such parts of the body as 

 the animal can reach with its tongue ; and thus, unconscious of what it is 

 doing, it unwarily introduces into its own citadel the troops of its enemy. 

 Another species (CE. hcemorrhoidalis) is still more troublesome to it, 

 ovipositing upon the lips ; and in its endeavours to effect this, from the 

 excessive titillation it occasions, giving the poor beast the most distressing 

 uneasiness. At the sight of this fly horses are always much agitated, 

 tossing their heads about in the air to drive it away ^ and, if this does not 

 answer, galloping off to a distant part of their pasture, and, as their last 

 resource, taking refuge in the water, where the gad-flies never follow them. 

 We learn from Reaumur, that in France the grooms, when they observe 

 any bots (which is the vulgar name for the larvae and pupae of these flies) 

 about the anus of a horse or in its dung, thrust their hand into the passage 

 to search for more; but this seems a useless precaution, which must 

 occasion the animal great pain to answer no good end ; for when the bots 

 are passing through the body, having ceased feeding, they can do no further 

 injury. In Sweden, as De Geer informs us, they act much more sensibly: 

 those that have the care of horses are accustomed to clean their mouths 

 and throats with a particular kind of brush, by which method they free 

 them from these disagreeable inmates before they have got into the stomach, 

 or can be at all prejudicial to them. 3 



Providence has doubtless created these animals to answer some benefi- 

 cial purpose; and Mr. Clark's judicious conjectures are an index which 

 points to the very kind of good our cattle may derive from them, as acting 

 the part of perpetual stimuli or blisters : yet when they exceed certain 

 limits, as is often the case with similar animals employed for purposes 

 equally beneficial, they become certainly the causes of disease, and some- 

 times of death. 



How troublesome and teasing is that cloud of flies (Anthomyia meteoricd) 

 which you must often have noticed in your summer rides hovering round 

 the head and neck of your horse, accompanying him as he goes, and causing 

 a perpetual tossing of the former ! 4 And still more annoying in Lap- 

 land, as we learn from Linne 5 , is the furious assault of the minute horse- 

 gnat (Culex equinus L.), which infests these beasts in infinite numbers, 

 running under the mane and amongst the hair, and piercing the skin to 

 suck their blood. - An insect of the same genus is related to attack them 

 in a particular district in India in so tremendous a manner as to cause in- 



1 De Geer, vii. 158. 



2 See Mr. W. S. MacLeay in Linn. Trans, xiv. 355. 



5 De Geer, vi. 295. * Amcen. Acad. iii. 358. 



6 Linn. Flor. Lapp. 376. Lack. Lapp. i. 233, 234. This insect from Linnets 

 description is probably no Culex, but perhaps a Simuliutn Latr. (Simulia 

 Meig.) 



