124 



ENTOMOLOGY FOR MEDICAL OFFICERS 



mandibles being very sharply serrated for some distance 

 along the inner edge, and the maxillae along the outer edge. 

 The maxillary palps, which are long and flexible, consist of 

 4 segments, and in the 2nd segment there is a sensory 

 vesicle with a minute opening to the surface. 



The species are extremely numerous, are represented 

 under suitable conditions in all parts of the world, and are 

 all included in the one genus Simuliuin. The females are 

 insatiable blood-suckers, active by day. In some countries 

 they appear, at certain seasons, in swarms, and attack cattle 

 and other domestic animals with fatal effect. A Himalayan 



mcufn-fan-C ^^j 



anTi^Ie^,- 



nerve C: 



brain 



inl: 



mandr- 

 ^ max.p. labellum 



Fig. 30. — Head of Simnlium, 



saJiv.gl. 



-sucker 



Fig. 31. — Smwiium Larva. 



species has been said to kill even human beings in the 

 same way; but whether in these cases death is caused — 

 as in the analagous cases of death from the attack of a 

 swarm of bees — by a multitude of envenomed wounds, or 

 is due to the inoculation of some pathogenic microbe is not 

 known. It cannot be affirmed that Simulium is a " carrier," 

 so far as man is concerned ; but from certain coincidences 

 in the geographical and physiographical distribution of 

 Simulium on the one hand, and the endemic and seasonal 

 prevalence of pellagra on the other, Dr Sambon assumes that 

 there is some causal connection between the fly and the 

 disease. 



The eggs of Simulium are laid in gelatinous masses on 



