310 American Fisheries Society 



where we rear the most of our black bass. We have there practically 



the same species of black fly. The men thought they were worms at 



but the bass knew what they were and what to do with them. 



Mr. Meehan: Is the fly itself a nuisance? 



Dr. Beax : Xot at all. 



Dr. S. A. Forbes, Urbana. 111.: I can answer some of the question 

 asked concerning Simulium or black fly. We have, in fact, been making 

 special studies of this insect along the Illinois River during the last 

 two years, taking the subject up at the request of the Pellagra Commis- 

 sion of the State of Illinois because the black fly has been suspected by 

 physicians of being concerned in the conveyance of pellagra from 

 n to person. 



Black flies are comm< n ail over the country wherever conditions are 

 fit for their multiplication. They must have running water with a 

 :derable current, and will not breed in stagnant or sluggish water. 

 We find the larvae, for example, in the larger rivers of the Mississippi 

 system only where there is something to arrest the current and create 

 a ripple over an obstruction. Where a mass of drift-wood becomes 

 packed together in a way to check the movement of the stream, the 

 surface of this submerged wood will often become black with these 

 larva?, which hatch there by myriads, and can perhaps be found no- 

 where else in the stream. The adults thus become an enormous nui- 

 sance, the fly itself being a pestiferous creature, as violent as a bee and 

 rsistent as a mosquito. 



You will - juently. that if you want to get black fly larvae to 



g black bass, you must have some such conditions as I 



have described; that is. shallow water with a freely flowing current 



in which the larva; can live. They apparently require a certain degree 



^ration of the water which they do not get in stagnant situations. 



Mr. Meehax : Does the black fly actually convey the pellagra dis- 

 ease? That would be rather interesting t.> fishermen, because if it did 

 there might be some hesitation about introducing it. 



Dr. Forbes : Perhaps I ought not to have mentioned that matter, 

 because it is a point sti.l under discussion by physicians in this country. 

 Most of those who have investigated it seem highly skeptical of the 

 theory that the Simulium gnats are agents in the transmission of pel- 



ra. That idea sprang up in Italy, where one of the great authorities 

 on insects as carriers of disease. Dr. Sanbon, of London, was investi- 

 gating the cause of pellagra. He came to the provisional conclusion 

 that in Italy the black fly conveyed the disease: and our people in this 

 country then took the subject up. We have worked with it for two 

 years in Illinois, particularly in neighborhoods where pellagra has 

 shown up as a local disease, and we have failed to find any evidence 

 that the black fly has anything to do with it. 



Dr. Beax: I suppose there are a great many species of Simulium? 



Dr. Forbes : \ es. 



Dr. Bean- 1 am quite sure tl pellagra in Columbia County, 



