434 THE CANADIAN ENTOMOLOGIST 



THE SECONDARY HOST OF MYZUS CERASI. 



BY VV. A. ROSS, DOMINION ENTOMOLOGICAL LABORATORY, VINELAND 



STATION. ONT. 



On looking over some of the recent literature dealing with 

 MyziAS cerasi, the well known cherry aphis, we find that a difference 

 of opinion exists among entomologists as to whether the species 

 is migratory. Crosby (1) considers that the question is unsettled. 

 Sanderson (2) and O'Kane (3) say that so far as known the cherry 

 aphis has only one food plant. Gillette (4) states definitely that 

 M. cerasi lacks the alternating food habit. On the other hand, 

 Quaintance and Balder (5) claim that the species is migratory. 

 How are we to account for these apparently conflicting statements? 

 Is it possible that the species is partially monophagous and partialh' 

 migratory? Our observations lead us to believe that it is. Apterous 

 forms reside throughout the season on the primary host — cherry— 

 and in addition alata?, produced during the summer, migrate to and 

 establish colonies on a secondary host. In Ontario, according to 

 our observations, the favourite alternate host is wild peppergrass, 

 Lepidium apelalum. We have made several collections of cerasi 

 from this weed and in migratory tests we have repeatedly been 

 successful in transferring the louse from the cherry to the wild 

 peppergrass. No doubt other crucifers serve as summer hosts. 

 In our insectary experiments we have succeeded in establishing 

 colonies of cerasi on Capsella bursa- pastoris, Brassica arvensis, and 

 Erysimum cheiranthoides, but so far these results have not been 

 verified in the field. 



Literature Cited. 



1. Slingerland and Crosby. Manual of Fruit Insects, p. 312. 



2. Sanderson, E. D. Insect Pests of Farm^ Garden and Orchard, 



p. 666. 



3. O'Kane, W. C. Injurious Insects, p. 318 



4. Gillette, C. P. The Monthly Bulletin of State Commission of 



Horticulture, California, Vol. VI, No. 2, p. 63. ' 



o. Quaintance and Baker. Farmers' Bulletin 804, U. S. Dept. of 

 '^ Agr., p, 24. 



December, 1917 



