94 



through Mr. George R. Stephenson, who reported its occurrence in that 

 locality the previous summer. 



By the summer of 1889 the pest had extended in numbers much far- 

 ther to the southward, and the Department was early informed of its 

 occurrence in Harford and Howard Counties, Md., and Prince William, 

 Fauquier, Stafford, Culpeper, Louisa, Augusta, Buckingham, and Bed- 

 ford Counties, Va. The alarm became so great that we were anxious 

 to learn all that was possible about the species, and arranged to have 

 it investigated. Considerable time has therefore been devoted to the 

 study of the habits and life history of the insect. This was done mainly 

 by Mr. Howard, who made a number of short trips to The Plains, War- 

 renton, and Calverton during June and July. Later in the season Mr. 

 Marlatt assisted in the work, which had been greatly facilitated by 

 Mr. G. M. Bastable, Mr. David Whittaker, Mr. M. M. Green, and Mr. 

 William Johnson, and particularly by Col. Robert Beverly. To the 

 courtesies of these gentlemen we would acknowledge our indebtedness. 

 August 20 Mr. Howard found the flies jjractically in Washington — in 

 Georgetown — and the next day Mr. Marlatt found them in Rosslyn, at 

 the Virginia end of the Aqueduct Bridge, so that further trips for ma- 

 terial were not necessary. 





Fig. 12.— HiEMATOBiA SERRATA: a. sido view of head of larva; b, ventral view of head of 

 larva, showing antenniP and thoracic stigninfa; c, dorsal view of anal en^ of larva, showing 

 anal stigmata; d, anal plate of puparium; c, ventral view of anal end of larva, showing 

 anal plate — still more oulargert. (Original.) 



The result of the summer's observations b^^ these two gentlemen is 

 that the life history of the insect has been accurately made out from 

 the egg to the fly through several consecutive generations, and that 

 substances can be recommended which, from their experience, will 

 keep the flies away for from five to six days, while from the life history 



