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THE SIMULIUM-PELLAGRA PROBLEM IN ILLINOIS. 



U.S.A. 



By Stephen A. Forbes, Illinois. 



The advancement of entomology owes much, of recent years, 

 to the stimulus suppHed by the discoveries made by medical 

 men with respect to the agency of insects in the transmission 

 of contagious diseases ; and just now our knowledge of the 

 species, distribution, habits, life histories, and ecology of Simulium 

 is progressing by leaps and bounds in consequence of the well- 

 known Simulium theory of the transmission of pellagra, announced 

 by Dr. Louis \V. Sambon in 1905, and fully elaborated by him 

 in the Journal of Tropical Medicine and Hygiene, in iqio. 



This stimulus to a study of these insects reached me, in one 

 of the interior States of North America, in August 1910, when, 

 in consequence of the appointment by the Governor of Illinois 

 of a State commission for the investigation of pellagra as occur- 

 ring in the insane asylums and other institutions of that State, 

 I was requested, as the official Entomologist of Illinois, to con- 

 tribute to their report an account of the distribution of Simulium, 

 especially in the neighbourhood of State institutions in which 

 cases of pellagra were occurring. As an investigation of all 

 insects injurious or dangerous to the public health in Illinois 

 is one of the prescribed duties of my ofñce, I was bound to avail 

 myself, to the best of my ability, of this opportune call. This 

 I did by detailing an assistant, Mr. C. A. Hart, August 8th, 

 iQio, to commence observations and collections along the central 

 part of the course of the Illinois River, and especially to make 

 a careful survey of the vicinity of the General Hospital for the 

 Insane, built upon a blufty bank of that stream near the city 

 of Peoria. My reason for giving particular attention to this 

 asylum was the fact that it had been the principal seat of pellagra 

 in Illinois, containing in 1909 80 per cent, of the cases of this 



