406 



many eggs were found is known as "Peterson's Seedling" or "Peterson's Drupe," 

 the nearest approach to a wild plum which we have here. I have advised the burn- 

 ing of these (useless) thickets. Doubting Thomases say : " How can you prove to us 

 that those eggs on the plum are not those of some other aphis, plum aphis for 

 instance ?" And I reply by saying that the plum aphis does not begin to be abundant 

 enough in this section to produce a tenth part as many eggs ; further, I fall back 

 upon the result of your investigations in Europe and America, and also the fact that 

 I have observed Phorodon on the plum in large numbers this fall earlier in the season. 

 I can not show them an egg of the plum aphis for comparison, even if there is a differ- 

 ence between the two. Neither can I with certainty obtain any plum aphis eggs. 

 Could you conveniently send me a few eggs of this latter insect now? Upon my 

 inquiring of them, hop growers, as to whether they burned their vines immediately 

 after gathering the fruit, they invariably replied they did do that, but further 

 inquiry elicited the fact that said burning does not take place until alter the vine is 

 all withered, when the louse has left them. I pointed this out to them and urged 

 very strongly indeed their burning the green vines immediately after picking, as they 

 pick. Does not this agree with your idea? 



The fact that I have found the Phorodon on plums at least 2 miles from hops leads 

 me to ask if I understand your statement in your summary (1888 Report) that "they 

 do not migrate readily from one hop yard to another." I found no eggs upon the fol- 

 lowing trees, though growing among the hops: Bradshaw plum, yellow egg plum, 

 Italian prunes, Petite Bows. Two damsons growing in the same situation Mere 

 not examined, but will be shortly, and the result with cuttings sent to me at Corval- 

 lis. I should be gratified lo hear expressions of your opinion on various points in 

 this letter, and if you could oblige me in the particular of Plum Aphis eggs I should 

 appreciate the favor. — [F. L. Washburn, Corvallis, Oreg>n, November 30, 1890. 



Reply. — I am much interested in your letter of the 30th ultimo and am pleased to 

 learn that you have so speedily fulfilled my predictions with regard to the stocking 

 of plum by return migrant Phorodon. Your iuloruiatiou regarding the variety of 

 plums infested als:> interests me. As to distinguishing the eggs of Phorodon from 

 those of other pliim-hibernating Aphididse, I can hardly assist you by sending you 

 authentic eggs of what you call " Plum Aphis," for the reason that there are several 

 plant lice which oviposit upon Plum in the fall in the Eastern States and in England, 

 and I am not sure which one, if any of these, you have in your vicinity. It is safe 

 to say, however, where Phorodon has been migrating in its usual numbers from hop 

 to Plum that its eggs will so vastly exceed in number those of any other species that 

 you can not fail to recognize them. I may say, however, that the eggs of Aphis pruni, 

 which somewhat resemble those of Phorodon, are larger and rather lighter colored. 

 I certainly indorse your advice as to burning the old vines immediately after ]iickiug, 

 as this is what I have myself recommended. You have misunderstood my statement 

 which you quote, to the effect that the lice do not migrate readily from one hop yard 

 to another. To be more explicit, migration from hop yard to hop yard is through 

 wingless individuals, which is slow or even impossible at long distances, while the 

 winged return migrant instinctively quits such fields for Primus. The statement 

 above referred to means just what it says and nothing more, and in my complete re- 

 port (not yet published) I have called attention to the fact that the return migrant 

 generations in the fall will fly long distances in search of plums. This fact was also 

 brouo-ht out in Mr. Howard's notice of my investigation in the Country Gentleman of 

 November 17, 1887. In other words, the non-tendency to migrate to any distance 

 holds only as between hop yards.— [December 8, 1890.] 



A Southern Roach in a Northern Greenhouse. 



We send you by this day's mail a small box containing a live roach and a frond of 

 Lastrea aristata variegata (Fern). The roach was caught on the fern, and we have 

 every reason to believe that they are their enemies. I hope you may gain some facts 



