70 



were received from Mr. Youmans. The following recoinmendatious 

 were then made: 



U. S. Departmext of Agriculture, Division of Extomology, 



May 26, 1888. 



Dear Sir : I take pleasure in ackno wledgiug the receipt of yours of the 24th trans- 

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

 thanks the receipt of the volumes of the "Senate Report upon Methods of Busiut-ss 

 in the Executive Departments." The cockroaches 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, which was to use thoroughly and persist- 

 ently the California Buhach, which Mr. Townsend tells me you have already pur- 

 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 houses. 



Respectfully, yours, 



C. V. Riley. 



Mr. E. B. Youmans, 



Chief Clerk, Treasury Department. 



Entomologist. 



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



At our last meeting I gave some account of investigations which, u]> 

 to that time, I had made on the life-history of the Hop Plant-lonse, 

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

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

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

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

 arid left some facts covering the period from that 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 aud 

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

 the following from a communication to the Gardenerh Chronicle of Eng 

 land for October 22, 1887: 



"During the hop harvest (this j^ear 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, intluenced by tem- 

 l)erature and season. The first to get wings are agamic females, and 

 they instinctively leave the hop-yards and settle u[)on different varie- 

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

 young. Their flight is much intluenced by meteorological conditions, 

 but they swarm in the air during mild and pleasant days. On my very 



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

 Cleveland, Ohio, August 21, 1888. 



