70 



were received from Mr. Youinans. The followiug recommendatious 

 were theu made: 



U. S. Depaktmext of Agricultuke, Division of Entomology, 



May 26, 1888. 

 Dear Sir : I take pleasure in acknowledging tbe receipt of yonrs of the 24th trans- 

 mitting specimens of cockroaches from your building, and also acknowledge with 

 thanks the receipt of the volumes of the "Senate Eeport upon Methods of Business 

 in the Executive Departments." The coclcroaches sent are not the big Oriental Cock- 

 roach, as I had supposed from your description, but belong to the native species 

 known as Periplaneta americana, and it is quite evident that this insect alone is the 

 cause of the damage to your books. Under these circumstances I can add noth- 

 ing to my verbal advice of the other day, wliich was to use thoroughly and persist- 

 ently the California Buhach, which Mr. Townseud tells me you have already pux-- 

 chased. This substance does not act upon the roaches instantly, but very few recover 

 which have been touched by it, although they may take a day or so in dying. It has 

 been used with great success in badly-infested bouses. 



Respectfullv, yours, 



C. V. Riley, 



Entomolofjist. 

 Mr. E. B. YoUMANS, 



Chief Clerk, Treasurij Department. 



FURTHER NOTES ON THE HOP PLANT-LOUSE (Phorodon humuli).* 



At our last meeting I gave some account of investigations wliicb, up 

 to that time, 1 had made on the life-history of the Hop Plant-louse, 

 proving that it does not hibernate on the grouud nor in any part of the 

 hop-yards, but that it migrates in autumu from the Hop to different 

 species of Plum, both wild and cultivated, and winters on the twigs of 

 the same in the Q^g state. That communication was made in August, 

 and left some facts covering the period from tliat time until the ensuing 

 spring problematical and to be ascertained by further investigation. I 

 have since persistently followed up the matter, both in this country and 

 in Europe, and can best supplement the article of a year ago by quoting 

 the following from a communication to the Gardener's Chronicle of Eng- 

 land for October 22, 1887: 



"During the hop harvest (this year in Kent at its height the last week 

 in September), and some time prior thereto, the insects are fast getting 

 wings. This is the only winged generation produced on the Hop, and 

 all individuals, irrespective of brood, show the tendency to become 

 winged, so thoroughly is aphid life, like plant life, influenced by tem- 

 perature and season. The first to get wings are agamic females, and 

 they instinctively leave the hop-yards and settle upon different varie- 

 ties and speciea of Prunus, and begin at once to breed and bring forth 

 young. Their flight is much influenced by meteorological conditions, 

 but they swarm in the air during miUl ami pleasant days. On mj' very 



* Paper by C. V. Riley before the Society for the Promotion of Agricultural Science, 



Cleveland, Ohio, August 21, 1888. 



