154 PLUM. 



to below,* from ^Yhicll I extract some of the leading points ; 

 and also, as during Prof. Eiley's stay in England I was 

 favoured by communication with him regarding autumn 

 migration of which details had not previously been recorded, 

 I give some extracts from letters from him to myself on this 

 subject. 



Some few of the leading points of Prof. Eiley's observations 

 may be shortly stated as follows. Phorodou JinmuU hyber- 

 nates in the winter egg state ; the little glossy black ovoid 

 eggs are fastened to the twigs (generally the previous year's 

 growth) of different varieties and species of Primus, both wild 

 and cultivated, and are especially found in tbe more or less 

 protected crevices around the buds. The egg is difficult to 

 detect because it is covered with particles which resemble the 

 bark in colour and appearance. They are usually not more 

 than four or five in number. 



From these eggs the aphides hatch which are the mothers 

 of the coming infestation ; the colour pale green, and "the 

 tubercles between the lionis hardly observable." Three gene- 

 rations are produced upon the Plum, the third of which 

 becomes winged, and instinctively abandons the Plum and 

 migrates to Hamulus, that is, to the Hop plant. 



A number of generations are produced upon the Hop (all 

 without occurrence of the male sex) until in autumn winged 

 females are produced, known as the return migrants, which 

 fly instinctively to the Plum. Here they settle, and in the 

 course of a few days (according to weather) each produces 

 some three or four young. " These are destined never to 

 become winged, and are true sexual females." Somewhat 

 later, on the Hop, the true winged male, the only male of the 

 ivhole series, is developed, and these males also congregate 

 upon the Plum, on the leaves of which, toward the end of the 

 season, they may be found ]>airing with the wingless females, 

 which stock the tw-igs with the winter eggs. Such briefly is 

 the life-history. 



In regard to dates in tJds country of the above described 

 autumn migration. In the year 1887 Prof. Puley wrote to 

 me, on September 15th, from Maidstone in Kent: — "As I 

 anticipated, I have found Phorodon Jtunmli just migrating 

 from Hop to Prune, and first wingless generation on Prune, 

 but no eggs yet." On September 24th, also, writing from 



* Paper by Prof. C. V. Kiley read before Section D of the British Association 

 for the Advancement of Science, Manchester, Sept. 3rd, 1887. " Notes on tlie 

 Hop Plant Louse," paper by Prof. C. V. Eiley read before the Society for the 

 Promotion of Agricultural Science, Cleveland, Ohio, U.S.A., August 21st, 1888. 

 See also ' Insect Life,' United States Department of Agriculture, vol. i. pp. 70-74 ; 

 and "The Hop Plant Louse," pp. 133-137 of same volume. Likewise 'Eleventh 

 Annual Report on Injurious Insects,' by myself, pp. 84-86. — E. A. O. 



