Insects. 



6173 



with his fore foot against the ground, and often strike with his foot 

 as though aiming a blow at the fly. They also sometimes hide them- 

 selves in the grass ; and, as the horse stoops to graze, they dart on the 

 mouth or hps, and are always observed to poise themselves during a 

 few seconds in the air, while the egg is preparing on the point of the 

 abdomen." 



Why this species should cause the horse so much annoyance, and 

 the other not any, in effecting the very same object, is one of the many 

 mysteries in the dispensation of things. The common Dhauma snake 

 {Colube?^ mucosas) and the Cobra Capella both prey habitually on 

 rats, and have the same foes to contend wdth ; and why, therefore, 

 should the one be perfectly innocuous, and the other so frightfully 

 venomous ? 



But it is time to return to Mr. Clark's mal-identification of the 

 tzetze with the European Hypoderma Bovis. In the ^Zoologist' 

 (Zool. 5720), the veteran naturalist remarks, that ^' a considerable de- 

 gree of uncertainty and even misapprehension appears to prevail about 

 the fly that Dr. Livingstone so interestingly describes as annoying 

 the cattle in Africa, and which he designates the tzetze, its African 

 appellation. Although introduced as a new species, I beg to observe 

 that it is a very old one under a new name, the fly so feelingly described 

 by Moses of old as infesting the cattle of Egypt, and by Isaiah as being 

 very troublesome in his day ; and after these the heathen writers and 

 poets, especially of Rome, do not fail to notice it. The fly itself, the 

 cause of this trouble, has been exceedingly scarce [in collections]. 

 * * * Now this African tzetze, I am led to believe, is the real 

 patronymic of the French Estre, made more pronounceable by intro- 

 ducing more vowels and fewer consonants, and then from it we get 

 the Latin (Estrus and the Greek Oislro?i, and so forth, all meaning 

 the same cattle-frighting object noticed by all : and so terrific is the 

 fright that the cattle will run away with their plough even through the 

 opposing hedge rather than submit to their infliction ; and yet, what 

 is most curious, they possess no weapon of infliction, but simply a 

 telescopic sort of tube for thrusting the egg down upon the skin, 

 which, hatching there, the tiny grub gnaws its way through the skin 

 and forms its nidus there in a comfortable abscess, leaving its abode 

 when fully grown, and tumbling to the earth, becomes a chrysalis and 

 next a fly, which goes forth to perform this strange round of events ; 

 the object of which appears to be to save the poor cow and ox from 

 the effects of idleness and repletion, which, in those sunny regions, 

 they would be so exposed to, if not roused into activity and leeched 



