Miss Haviland, Note on Antennal Variation in an Aphis 35 



Preliminary Note on Antennal Variation in an Aphis (Myzus 

 ribis, Linn.). By Maud D. Haviland, Fellow of Newnham 

 College. (Communicated by Mr H. H. Brindley.) 



[Read 8 March 1920.J 



In 1918, during an investigation of the life-history of the Red 

 Currant Aphis, Myzus ribis, Linn., it was observed that consider- 

 able variation occurred in the antennae of the winged partheno- 

 genetic females; and the evidence pointed to the conclusion that 

 this variation was induced by the food^. Antennal variation in 

 certain Aphididae has been studied by Warren ^ Kelly^ Ewing- 

 and Agar^. Warren's experiments on Hyalopterus trirhodus 

 showed some diminution of the correlation co-efficient in passing 

 back from parent to grandparent. Kelly, for Aphis rumicis, con- 

 sidered that somatic variations of the parents were not inherited 

 by the offspring. Ewing, who bred eighty-seven generations of 

 Aphis avenae, concluded that the variations were not transmitted 

 to the offspring. 



Agar found some evidence of a partial inheritance of individual 

 variations in Macrosiphum antherini, but he showed that this 

 might be due to causes other than true inheritance. 



Myzus ribis is a common pest of red currant bushes. The 

 sucking of the aphides upon the leaves tends to cause red galls or 

 blisters, within which the plant lice continue to feed and reproduce. 

 The fifth and sixth antennal segments of the winged partheno- 

 genetic females normally bear two sense organs of unknown 

 function — one on the distal third of Seg. v., the other on the 

 proximal third of Seg. vi. It was observed in 1918 that, in indivi- 

 duals reared on red blistered leaves, these sensoria were placed 

 comparatively close to the articulation of Segs. v. and vi. On the 

 other hand, if the aphides were fed upon green unblistered leaves, 

 the sensoria were placed further away from the articulation. 



For the sake of brevity, the first type of antenna will be referred 

 to hereafter as the Red (or R) type, and the second as the Green 

 (or G) type; but every degree of transition may exist between the 

 two extreme types. 



The experiments of 1918 were incomplete, and were conducted 

 with a polyclonal population. They were repeated in 1919 with a 

 monoclonal population, but the results are still far from being- 

 conclusive owing to the small numbers available in some genera- 

 tions. Only the winged forms show the required character. The 

 production of these forms is probably governed by environmental 

 factors which at present are imperfectly understood, and, for some 



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