306 



DR. P. MANSON ON THE DEVELOPMENT 



the skin. As the male is provided with a complete alimentary 

 apparatus, it is presumed that he feeds on the juices and exuda- 

 tions of plants and fruits. There are two species of mosquito 

 found during the summer here : one quite a large insect about 

 half an inch long, with a black thorax and black-and-white banded 

 abdomen ; the other about half that size and of a dingy brown 

 colour. The former is rare comparatively ; the latter is very 

 common, and is the insect my remarks apply to. After a mos- 

 quito has filled itself with blood (which it can do, if not disturbed, 

 in about two minutes), it is evidently much embarrassed by the 

 weight of its distended abdomen, so that it no longer can wheel 

 about in the air. It accordingly attaches itself to some surface, 

 if possible near stagnant water, where it remains in a compara- 

 tively torpid condition, digesting the blood, excreting yellow 

 gamboge-looking faeces, and maturing its ova. In the course ot 

 from three to five days these processes are completed, and the 

 insect now betakes itself to the water, where the eggs are depo- 

 sited, and on the surface of which they float in a dark-brown 

 mass, looking like a flake of soot. The eggs do not take long to 

 hatch (they are beautifully shaped objects, like an Etruscan vase) ; 

 and the embryo emerges by forcing open a sort of lid placed at 

 the broad end of the shell. The larvae now escape into the water, 

 where they swim about and feed, and become the "jumpers" we 

 are familiar with, found in every stagnant pool. 



If the contents of the abdomen are examined before the mos- 

 quito has fed, or after the food has been absorbed, the following 

 parts can easily be distinguished : — two ovisacs containing from 

 sixty to a hundred ova, two large glandular masses (intestine and 

 oesophagus), and a very delicate transparent fibrous bag, the sto- 

 mach. If the blood contained in the dilated stomach is examined 

 soon after ingestion, the blood-corpuscles are seen quite distinct 

 in outline, and behaving very much as when drawn in the ordi- 

 nary way ; but changes rapidly occur. Pirst, the corpuscles lose 

 their distinctness in outline, then crystals of haematin appear ; 

 corpuscles and crystals give place to large oil-globules, and the 

 mass is deprived of its fluidity, and before the eggs are deposited 

 all colouring-matter disappears ; the white material is absorbed or 

 expelled, and by the time the eggs are deposited the stomach is 

 quite empty but for the embryo FilaricB it may contain. 



How to procure Mosquitos containing embryo Filariae. — It may 

 be useful to those who wish to repeat and test my observations 



