KI.M ! i;.\! ; Cl'KI, AM) \VOOI.1A' AIM'I,!' Al'illJ). 241 



colonies are originated bv the stem mother, or bv migrant.- in>m 

 the leaf curl or both; whether the mid June i in Maine i winged 

 fi nils from the elm bark colonies migrate 1 to apple- or scatter to 

 other e-hn bark, or both; the significance oi the difference in 

 antennal tvpcs of migrants I roni elm leal curl ( I'igs. 45 ' 45-' 

 4^4. an 1 4S^ ) . \vluther in licating locality or conditional varia- 

 tion ; and complete sequence upon each food ])lant : are subjects 

 f< >r I urth.er sin 'y. 



These points can for the most part be watched onlf with 

 colonies upon seedling stock of the food plants in confinement 

 under such conditions that perfect control of the material can 

 be secure '. \Vh:lc 1 have further work along these lines already 

 tinder way, some of the problems will need extended observa- 

 tion- and it has seemed desirable not to wait until all tangles 

 are straightened out before 'publishing the main fact of the 

 migration test from elm leaf curl to apple bark as this point has 

 an important bearing for young trees m nurseries and new 

 orchards and the economic significance of the migration delta 

 will not, so tar as can be anticipated, be influenced by further 

 detailed studv of the different generations. 



Tin-; Si'Ri XG M M',K.\TI"' >\. 



The fact of the migration from elm leaf to apple and moun- 

 tain ash under normal out of door conditions was established 

 (hiring the summer of injj. The migrants from the elm leaves 

 settle on the under side of the apple leaves of water shoots and 



there congregate in woolly masses. The mountain ashes (P\ri(s 

 aiiicricana and introduced species) are favorite summer hosts in 

 Maine. Fr-mi one native mountain ash at Orono more' than 

 400 such migrants were removed July 2 to July 12 from the 

 ventral surface of the leave's, and about 150 thriving clusters of 

 woolly aphid nymphs, the immediate progeny of these migrant-. 

 were established on the shoots of this single tree. :i: 



In this connection it may be ot interest to record a forced 

 migration test. ( )n June 21. KM 2. 1 placed several hundred elm 



* A nii>re detailed .'u'omr.t i>f this <>ccurreiKv is to be published in 

 the October issue of the Journal of l ; ,conomic Kmomoloin,-. 



