INJURIOUS INSECTS OF 1005 IN MINNESOTA. 87 



been done in the elimination of the Mediterranean flour moth (Ephes- 

 tia kuehniella Zell.) from a large mill. This mill is six or seven 

 stories high, and we fumigated not only the mill proper but the 

 warehouse, cleaning house, and elevator, amounting in all to over 

 3,000,000 cubic feet of space. We used a ton of cyanide of potash 

 and a ton and a half of sulphuric acid. The operation was in every 

 way successful. The bags of cyanide w T ere lowered into the crocks 

 on all of the stories from the outside without a hitch, and ventilation 

 secured equally easily on all the stories. 



A curious accident, if it might be called such, occurring after the 

 fumigation — an accident which might happen in any such operation, 

 probably, but since it would occur when the building was open for 

 ventilation, would hardly result disastrously — came to our attention. 

 We were in the mill, and the men were removing the crocks, when one 

 of them came running to me, with a somewhat pale face, stating that 

 when he took hold of the string to lift the fragment of the bag from 

 the jar a piece of cyanide almost as big as his fist dropped into the 

 acid and gas began immediately to be given off. It w T as an easy mat- 

 ter to shut off that room from the other part of the mill, where the 

 men were working, and the open windows soon carried off the deadly 

 fumes. Apparently, in tying the cyanide up in the paper bag a piece, 

 probably not as large as the man in his excitement supposed, had be- 

 come fastened in the conical top of the package and was held there 

 by the paper until the bag was shaken. 



A question of some interest to entomologists was raised in connec- 

 tion with this work, upon which I should be glad to hear your opin- 

 ion, namely, as to what constitutes successful fumigation in a flour 

 mill. After the operation to which I refer was finished, several of us 

 made a careful search through the mill, and in some of the fine flour 

 which had gathered at the base of the spouts on the first floor we 

 found two living worms among the thousands of dead ones, and 

 later one living moth was found flying in the mill. This firm at 

 first made the absurd claim that the operation was not successful, 

 since they had found these three living insects. I believe I convinced 

 them, however, that they were mistaken in their judgment, arguing 

 that in a mill infested as theirs was there were many millions of 

 moths in some stage before the mill was in such a condition as to 

 call for the radical treatment we had just given it, and that even if 

 we found twenty times that number of larvae after fumigation, and 

 half of those larvae should, barring accidents, transform into female 

 moths and lay eggs, it w T ould nevertheless be a number of years be- 

 fore the mill would be sufficiently infested from this source to need 

 another treatment. They finally yielded my point. Since this mat- 

 ter may present itself to any one of us, it may be worthy of a 

 moment's consideration upon your part. Of course, the best time to 



