596 THE MICROSCOPE. 



sands of eggs, larvae, and flies, and this is repeated again 

 and again until the whole brood is destroyed by winter's 

 cold. 1 



The " Tsetse" fly of tropical Africa (Glossina morsitans): 

 the mouth, proboscis, and piercing apparatus of one, viewed 

 from the under-side, is represented in Plate VI. ^N"o. 131. 

 The biting apparatus consists of four parts, of which two 

 are lateral setose palpi ; if a horny case for the protection 

 of the proboscis and its contained style can be so called. 

 The palpi, although arising from two roots, when joined 

 together, and accurately embracing the proboscis, as they 

 will do when the fly is at rest, appear as one only ; but 

 when the insect is in the act of piercing or sucking, they 

 divide, and are thrown directly upwards. The palpi are 

 furnished on the outer, or convex sides, with long and 

 .sharply pointed, dark-brown setae or hairs; while the 

 inner or concave sides which are brought in contact with 

 the proboscis are perfectly smooth and fleshy. Three cir- 

 cular openings seem to indicate the tubular character of 

 what in the common fly is a fleshy, expanded, and highly- 

 developed muscular proboscis : in the Glossina it is a 

 straight, horny-looking, red-coloured bristle, the apex of 

 which is slightly dilated and rounded, and apparently 

 barbed, while it expands a little towards the base, and 

 there dilates into a large-sized fleshy bag, or muscular sac, 

 filled with a red-coloured fluid. The proboscis is grooved 

 on the under-side for the purpose of receiving a slender 

 glassy style, acutely pointed, and equal to it in length. 

 The style, nicely adapted to the groove, and taking its 

 rise from the poison gland, is the penetrating instrument. 

 A series of long and thin muscular bands embrace this 

 gland, and their tendinous insertions are so arranged as to 

 bring considerable force to bear upon its contents. Phy- 

 siological science has made us familiar with the fact, that 



(1) Dead flies may be constantly observed, about autumn, surrounded by a 

 sort of halo, which, upon examination, is found to consist of the spores of a 

 fungus. The abdomen is much distended, and the rings composing it are 

 separated from each other, the intervals being occupied by white prominent 

 xones, constituted of a fungoid growth proceeding from the interior of the 

 body. Further examination will show that the whole of the contents or the 

 body of the fly have been consumed by the parasitic growth, and that nothing 

 remains but an empty shell, lined with a thin felt-like layer composed of the 

 interlaced mycelia of the innumerable fungi. See Dr. F. Cohn's observation 

 upon the parasite in vol. v. p. 154, Jon^n. Micros. Sci. 1857. 



