22 Guide to Insects and Ticks 



TSETSE-FLIES AND TRYPANOSOMIASIS. 



Trypanosomiasis is a general term applied to diseases caused 

 by species of Trypanosomes, small blood-parasites of an animal 

 nature, belonging to the division of the Protozoa known as the 

 Haemoflagellata. 



Tsetse-flies are African, blood-sucking, dipterous insects, with 

 peculiarly modified, piercing mouth-parts. The blood-sucking 

 habit in tsetse-flies is common to both sexes, whereas in 

 mosquitoes the females alone suck blood. The virus of the 

 disease is introduced into the blood by the proboscis of the 

 infected insect at the time of the bite. 



In one of the cases in the middle part of the Hall, near the 

 statue of Sir Eichard Owen, is shown a large model ( x 28) of one 

 of the tsetse-flies, Glossina morsitans Westw., which is mainly 

 responsible for the spread of a deadly disease— nagana — among 

 domesticated animals. In the blood of African animals, such as 

 antelopes and buffaloes, there is frequently found a parasite, 

 TnjiKinosoma brucei Plimmer and Bradford, which apparently 

 causes little inconvenience to the host, but this, if transferred to 

 a horse, ox or dog by the piercing proboscis of a tsetse-fly that has 

 previously fed upon the blood of an infected antelope, gives rise j;o 

 the nagana or tsetse-fly disease. The fatal disease of man known 

 as sleeping sickness is spread by the tsetse-flies Glossina palpalis 

 Eob.-Desv. (fig. 6, p. 25) and G. morsitans Westw. The organisms 

 causing sleeping sickness are Tnjpanosoma f/ambicusc Dutton (fig. 5) 

 and T. rliodcsioise Stephens and Fantham, in West and Central 

 Africa and North-east Ehodesia respectively. 



In the same case are shown actual specimens of the tsetse- 

 flies Glossina morsitans and G. palpalis, and enlarged coloured 

 drawings ( X 2) of the under and side views of a specimen of 

 the former species, showing the collapsed and the gorged condition 

 of the abdomen before and after a meal of blood. Another drawing, 

 of the natural size, shows how the wings of a tsetse-fly overlap 

 one another above the abdomen when the insect is at rest. In the 

 glass vessel are four larvae at difl'erent stages of growth, and a 

 pupa, of Glossina palpalis. The end of the pupa-case that bears 

 the two projections is the hind end, as is explained in the enlarged 

 drawing ( x 12) placed alongside. 



Sketches are exhibited of a horse and a dog sufl'ering from 



