GRUB PARASITE IN THE SXAIL. 361 



afflict it with little pain. For this reason cattle most co- 

 vered with bumps are not considered by the farmer as 

 injured by the presence of the fly, which generally selects 

 those in the best condition. 



A fly, evidently of the same family with the preceding, 

 is described in Bruce's ' Travels,' under the name of zimb, 

 as burrowing during its grub state in the hides of the ele- 

 phant, the rhinoceros, the camel, and cattle. " It resem- 

 bles," he says, "the gad-fly in England, its motion being 

 more sudden and rapid than that of a bee. There is some- 

 thing peculiar in the sound or buzzing of this insect ; it is 

 a jarring noise together with a humming, which as soon as 

 it is heard all the cattle forsake their food and run wildly 

 about the plain, till they die, worn out with fatigue, fright, 

 and hunger. I have found," he adds, " some of these 

 tubercles upon almost every elephant and rhinoceros that I 

 have seen, and attribute them to this cause. When the 

 camel is attacked by this fly, his body, head, and legs break 

 out into large bosses, which swell, break, and putrefy, to 

 the certain destruction of the creature."* That camels die 

 under such symptoms, we do not doubt ; but we should 

 not, without more minutely-accurate observation, trace all 

 this to the breeze-fly. 



MM. Humboldt and Bonpland discovered, in South Ame- 

 rica, a species, probably of the same genus, which attacks 

 man himself. The perfect insect is about the size of our 

 common house-fly {Musca domesticd) , and the bump formed 

 by the grub, which is usually on the belly, is similar to that 

 caused by the ox breeze-fly. It requires six months to 

 come to maturity ; and if it is irritated it eats deeper into 

 the flesh, sometimes causing fatal inflammations. 



Grub Parasite in the Snail. 



During the summer of 1829, we discovered in the hole 

 of a garden-post, at Blackheath, one of the larger grey snail 

 shells (^Helix aspersa, Mullek) , with three white soft-bodied 

 grubs burrowing in the body of the snail. They evidently, 



* Bruce's Travels, i. 5, and v. 191. 



