86 
HOP. 
(the Phorodon Humuli that is) from Hop to Plum. The accounts of 
this he published at the time in more than one of our leading journals, 
hut I give a few of the most important points, from communications 
which I have been favoured with from himself, showing the progress 
of the movement on to Plum in the autumn. 
On September 15th Prof. Eiley wrote me from Maidstone,—“As I 
anticipated, I have found Phorodon Humuli just migrating from Hop 
to Prune, and first wingless generation on Prune, but no eggs yet.” 
On September 24th also, writing from the neigbourhood of Maid¬ 
stone, Prof. Eiley noted, “ Phorodon swarming on Plum-trees here.” 
On October 1st Prof. Eiley wrote me that he had now brought the 
Phorodon investigations to a successful close, and completed 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, and the first generation on the Plum is the sexed one.” 
Further, Prof. Eiley informed me that the Aphis eggs (which he 
had seen on the Plum-shoots) became black. This agrees with 
information sent me by various correspondents during the last few 
years, that they had noticed black eggs, of which they sent me 
specimens, from which they had no doubt they had hatched Hop Aphis. 
We have now got the complete circle of observation of the life- 
history of the Hop Aphis, as far as Hop and Plum and Sloe are con- 
concerned ; and it appears plain that washing in the Plum orchards 
betimes will cut off one great cause of infestation to the Hop, but in a 
further consideration, although I scarcely like to venture to differ in 
any way with such a thoroughly well-skilled observer as Prof. Eiley, 
yet, as we have discussed the point much in friendly conversation, I 
will venture to say that I do not myself think that in this country the 
whole of the attack comes on the wing from Plum, Damson, or Sloe. 
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. Also in the Stoke Edith experiments, made in 1884,* 
it was found that in the case of the Hop-hills which were dressed with 
applications to keep the Aphides from coming up from around the Hop- 
plant, the bines on these hills (more than six hundred in number) were 
free from attack, although the rest of the Hop-yard was infested , until the 
fly came on the wing about the end of May. 
This matter of the amount of attack to be found early in the 
season on Hop needs further enquiry, and I should be very much 
obliged by infested shoots of Hop being sent me as early in the season 
as they may be observed, for thorough identification of the species. 
* See my ‘ Report on Injurious Insects ’ for 1884. 
