February, '16] PATCH: aphid ECOLOGY 47 



It might be said that due recognition of this work identifying 

 Schizoneura corni of dogwood and S. venusta of grass roots has been 

 given in European Hterature (Mordwilko, 1907 ^) and the observations 

 verified exemphfying the adage concerning the prophet and his own 

 country. 



However, it is neither in defence of the investigation of 1889 (for it 

 can stand on its own merits) nor in criticism of the sceptical attitude 

 of some of our foremost entomologists on aphid matters (for I realize 

 that there is reason enough for caution), that I have devoted so much 

 space to the case of corni. It is introduced into this discussion because 

 it illustrates two phases of a problem with migratory aphids — that is 

 the initial difficulty of the investigator in getting at the facts and the 

 secondary difficulty of other people in accepting them. 



Considering the complexities involved, neither difficulty is to be 

 wondered at. Take tessellata, the common woolly aphid of the alder, 

 for instance, with its continuous presence during the summer in the 

 form of apterous females and during the winter as hibernating nymphs 

 upon the single food plant — what place has it in its life cycle for a 

 spring and fall migration from and to the maple? It was incredible 

 that the maple leaf Pemyhigus had anything to do with a species 

 having an all year existence on alder. I watched that situation for 

 four years before I dared publish it, but by that time I was not much 

 disturbed when a kindly entomologist wrote me a friendly letter to 

 explain that I had made a mistake, giving perfectly logical reasons to 

 show that P. acerifolii simply had to be a species distinct from P. 

 tessellata of the alder. There was absolutely nothing the matter with 

 his logic — but it didn't stop the maple migrations of P. tessellata — at 

 least in Maine. 



-Logically, the most absurd aphid case yet come to light is that of 

 Schizoneura lanigera. Why, any entomologist could ^it down and 

 write a book of reasons explaining why the woolly aphid of the apple 

 could have nothing to do with the elm leaf rosette. In the face of 

 these reasons I must confess to something akin to a nervous chill when 

 I first made sure that this common apple pest, with its perennially 

 unbroken residence upon apple roots in the form of apterous females 

 and its hibernating nymphs protected about the same tree, possesses 

 a third normal and annual over-wintering form — that is the egg in the 

 crevices of the elm bark from which hatches in the spring the stem 

 mother of S. lanigera, the rosette aphid of the elm — the grandmother 

 of the spring migrants to the apple. However, in spite of my own 

 fright (and possibly that of other entomologists as well?), the migrants 



11907. Biologische Centralblatt, XXVII Bd., No. 23. Beitrage zur Biologie 

 der Pflauzenlause, Aphidida; Passerini, p. 787. 



