HOP AND PLUM APHIS. 155 



the neighbourhood of Maidstone, Prof. Eiley noted, " Phorodon 

 swarming on Plum trees here." On October 1st Prof. Piiley 

 wrote me that he had now brought the Phorodon investigations 

 to a successful close, and completed his observations of the 

 whole life cycle : — " Last week pairing was everywhere going 

 on, and on Saturday I noticed the first eggs. The Plum trees 

 are now being rapidly stocked. The male is winged and the 

 female wingless, as I had surmised." Prof. Eiley further 

 informed me that the aphis eggs which he had seen on the 

 Plum shoots became black, and this agrees with the informa- 

 tion sent me for several years preceding 1887 whilst investi- 

 gations were going on, that they had noticed black eggs, from 

 which they had not any doubt that the aphis which they 

 hatched was Hop AjDhis. 



Prof. Eiley observed that although the winged emigrants 

 from the Hop preferred the Damson, yet they also fed and 

 bred on all other varieties of Plum which he had the oppor- 

 tunity of examining, including the Bullace, the Victoria, the 

 Black Diamond, the Yellow, the Greengage, and the Orleans. 



These observations relatively to migration, for full details 

 of which the reader is referred to works cited p. 154, coming 

 as they do from such a high authority as the late Prof. Eiley, 

 and also as being the result of his long-continued personal 

 investigations, give thorough confirmation to the belief pre- 

 viously much held as to Hop infestation coming on the wing 

 from Plum ; but still I do not myself think that in this 

 country, though much of the attack comes in this way, that 

 it is wholly so originated, and esiDecially with regard to the 

 very earliest appearances. 



I think this because we have found aphides (that is, wingless 

 females and lice) on Hop as early as the end of March and 

 the beginning of April, long before the attack coming on the 

 wing made its appearance. 



Just to give a few instances :— In 1884 Mr. C. Whitehead, 

 writing to me from Barming, Maidstone, on the 29th of 

 March, mentioned, "I have found the enclosed Hop shoot, 

 with the larv8B in situ, in my Hop ground this morning. 

 There was a wingless female, which had evidently deposited 

 viviparously the larvae enclosed. ... I dress late, and so 

 I have plenty of shoots which will soon be cut off, and upon 

 these I found the lice I sent to you. I went out in the 

 afternoon and found lice upon many of the hills, . . . where 

 there were small lice, in most cases a wingless viviparous 

 active female was not far off. I found them chiefly in a part 

 sheltered from cold winds, and where hatching or awakening 

 from hybernation would be early. I should say I found a 

 hundred at least in ten minutes." 



