HOP AND PLUM APHIS. 153 



So loDg ago as the year 1854 it was recorded by Prof. C. 

 L. Koch* in his work on aphides that he found Hop Aphis 

 on Plum and Sloe, and he mentioned the great numbers in 

 which- this species {Phorodon humidi) was to be found on these 

 trees or bushes in the latter part of May. He described the 

 species in its various conditions (that is, as female, young, 

 <!tc.) from what he saw on Plum and Sloe, and after giving 

 details of these he added : — " In the month of June this kind 

 of ai^his quits the leaves of the Sloe" (or wild Plum), "and 

 then betakes itself to the wild and cultivated Hop, where it 

 settles on the under side of the leaves, sometimes in immense 

 numbers." — (C. L. K.) 



From my own examination of specimens and collection of 

 observations of Hop Aphis attack during the latter part of 

 March to about the end of August in the year 1884 (and also 

 in subsequent years), and from comparison of published views 

 of entomologists who have paid especial attention to this kind 

 of aphis attack in England, Germany, and the United States 

 of America, there appears to me to be no reason to doubt that 

 a great part at least of the attack of "Green Fly" which 

 usually appears on Hops towards the end of May comes on 

 the wing from Plum, Damson, Sloe, or other plants of the 

 Plum kind, and may be certainly recognized as of the genus 

 Phorodon (Passerini) and of the species hiimidi (Schrank), 

 that is to say, what is commonly known as the Hop Aphis, 

 and is described by Buckton as Phorodon humuli, Schrank, 

 and Phorodon liumitli var. malahch, Fonsc.f 



It was not, however, until the long and careful observations 

 which were made by Prof. C. V. Eiley, the Entomologist of 

 the Board of Agriculture of the United States of America, 

 were carried out by him in America and in England (in this 

 country in the autumn of 1887) that we became possessed of 

 the knowledge of the whole life-history of this Hop Aphis 

 {P. liumidi) from its hybernation on the Plum in egg state, 

 and spring migration on the wing, in sequence up to the 

 details of its autumn existence at the time of its migration 

 back from the Hop to the Plum, and the laying of the eggs 

 to start the next year's brood. 



Details will be found in the papers by Prof. Eiley referred 



* 'Die Pflanzenliiuse (Aphiden),' von C. L. Koch, jap. 114-116. 



+ For some considerations published during 1897 as to standing of " malaheb " 

 as a variety of " hinniiU " or as a distinct species, see following notes under the 

 heading of Myziis malaheh. In my own observations I have considered malaheb 

 to be only a variety, as stated by Buckton to be his oi^inion (' British Aphides,' 

 vol. i. p. 168), together with his considerations and collation of opinion on this 

 subject of various writers; and also description, pp. 168-171, of P. humuli var. 

 malahch with notes of ih.e first antennal joint being gibbous in the females de- 

 scribed (and as figured, p. 1.52), as well as of existence of the frontal tubercle. 

 In si^elling of the word malaheb, I follow the different writers. — E. A.O. 



