6D 



S2 



Marvels of Insect Life, 



attacked. Now, the sting of such an Insect as a wasp is an offensive weapon designed 

 to secure the submission of its prey and for defensive purposes. It is situated 

 at the end of the hind-bodv and provided with poison glands ; but the instrument 

 of the tsetse-fly, as of the mosquito, is a development of the mouth-parts into a hollow 

 tube through which the victim's blood may be sucked. There were not wanting 

 entomological experts who held that an}^ unpleasantness following the operation 

 of the tsetse-flv was solelv due to mechanical irritation and the loss of a small 

 amount of blood. It was a mere coincidence, said they, that the flies had been 

 about the cattle before these were stricken with disease and death ; and 

 one well-known man spoke of the supposed connection of the fly and the disease 

 as a myth. Cattle that were penned in the native villages were safe : the 

 natives said because the flv avoided the neighbourhood of human filth. 



At this time it 

 was thought that 

 there was only one 

 kind of tsetse,^ and 

 consequentlv it was 

 spoken of as t/ic fl\^ 

 About ten years ago 

 more careful in- 

 vestigation showed 

 that there were seven 

 distinct species, and 

 no^^' our knowledge 

 has been increased 

 so rapidly that about 

 fifteen species are 

 known. These var\' 

 in size from a quarter 

 to half an inch in 



Photohy] [H.Boitui. 



A Tsetse-Flv. 

 The tsptse flies asannoyanccs to man and cattle have been well known Irom the sixteenth century, 

 but it is only within recent years that they have been disrovered to be the carrying agents by 

 which the healthy are inoculated with the germs of disease. 



length, 



and roughly 



speaking may be 

 said to be not unlike 

 our common house-fly in appearance. They are not generally distributed ovei 

 the country, but are often restricted to comparatively small areas known as 

 " fl3-belts." They appear to avoid extensive open tracts of grassland, and to demand 

 the cover of bush, forest, or reed-beds. The different species varv in colour from black 

 through brown of different tints to yellow ; and the beak or sucking organ when not 

 in use is carried extended in front of the head. One character of the tsetse-flies^ 

 though, not confined to them — is that the females do not deposit eggs, as do the 

 majority of flies, but retain them until they have hatched and developed into full- 

 grown yellow grubs. Only one grub is produced at a time, and as a rule it is deposited 

 on light sandy soil into which it immediately burrows and changes to the chrysalis 

 condition, from which it emerges as a fly five or six weeks later. ITnlike most blood- 

 sucking flies, the male tsetse as well as the female indulges in this objectionable habit. 



' Cilossina morsitans. 



