24 SOME MINUTE ANIMAL PARASITES 



which they live. The hot, clear atmosphere is 

 ideal for them, and in time the adult fly, Glossina 

 palpalis, emerges, and at once desires to feed. The 

 female fly is somewhat larger than her mate, and the 

 desire for food is strong in both sexes, the food 

 preferred being human blood. Flying a little inland, 

 rarely more than about 30 yards from the water, to a 

 village of huts, or along shore to a camp settlement 

 or ford, the Glossinae meet with man, and perhaps 

 some negro, whose emaciated body, intense lethargy, 

 and heavy breathing are evidences of his condition, 

 is encountered. The very slight buzz of the insects 

 does not arouse him, nor does he attempt to drive 

 them away. They poise above him, and then, with 

 a sudden swoop, the proboscides are plunged into 

 naked leg or arm, and the abdomens of the flies 

 become more and more distended as the blood of 

 the man, heavily laden with the infective trypano- 

 somes, passes into the flies. Gorged at last, they fly 

 away to digest their meal. But they are satisfied for 

 a short period only, and once more are on the wing 

 to find a new food-source. Working along the shore, 

 tormented by biting flies and other creeping insects, 

 is a young European, full of energy and skill. A 

 good host, though a black skin would be preferred ! 

 Amid other distractions, the stab of the Glossina is 

 unnoticed, but the damage is done. As the thrust 

 of the proboscis into the skin is made, the wriggling 

 trypanosomes swim forwards into the blood of the 

 new host. At first the parasites are very few in 

 number, but ere long they grow rapidly, and com- 

 mence to multiply by longitudinal division. The 



