Insects. 



6181 



has a Tabanus rather than an QEstrus for its origin." (That, surely, 

 was abundantly demonstrated by MacLeay). 



"The larva of (Estrus Bovis resides beneath the skin of the back of 

 the ox, causing large tumours, and having the extremity of its body 

 constantly placed at the orifice of the wound, where it was introduced 

 as an egg, or introduced itself as a grub, the openings of its respiratory 

 apparatus being placed at that part of the body. 



"These introductory remarks," continues Mr. Westwood, "on the 

 different modes in which insects attack our horses and oxen, and the 

 different effects which they produce, will enable us the better to esti- 

 mate the effects produced by an insect, or several species of insects, 

 of tropical Africa, upon the horses of travellers who have lately re- 

 turned from that part of the world, where their enterprising researches 

 have been rewarded by the discovery of the great central lake Tchad 

 [by the northern, and of lake Ngami and its tributaries by the southern 

 route]. Captain Frank Vardon, a gentleman who has travelled far 

 in the interior of Africa, has placed in my hands some fragments of 

 Dipterous insects which attacked his horses, causing the death of one 

 of them. The following is an extract from his note to me in reply to 

 my enquiry as to the mode of its attack : — 



' 1 had always heard that the fly of South Africa was a large 

 gadfly, the size of a bee or hornet. This is quite erroneous: it is 

 not very much larger than the common house fly, but a longer and 

 more rakish-looking insect, and easily distinguished by the transverse 

 black bars on its body. 



" 'I fancy it is not met with southward of the tropic of Capricorn. 

 It is usually found on hills, plains being free from it. I have ridden 

 up a hill and found the tzetze increasing at every step, till at last 

 forty or fifty would be on my horse at once. The specimens you 

 saw cost me one of the best in my stud. He was stung by some 

 ten or a dozen of them, and died in twenty days. I myself have been 

 bitten by the tzetze ; you would almost fancy it was a flea biting 

 you. Some parts of South Africa are, I should say, rendered inac- 

 cessible by the presence of this pest ; I mean of course to a man who 

 travels in the usual way, with his oxen and horses. 



" ' How far the tzetze extends in the interior is of course as yet 

 unknown, but I have certain information as to its being 200 miles 

 north of the " Great Lake " [Ngami] recently discovered by my friends, 

 Messrs. Livingstone, Oswell, and Murray.' " 



This formidable insect is minutely described by Mr. Westwood 

 under the name Glossina morsitans ; and of a remarkable structural 



