A Method of obtaining Phloem Sap via the Mouth-parts of Aphids

Abstract

ALTHOUGH aphids and coccids are known as ‘sucking’ insects, suggestions have been made from time to time1 that forces within the plant, set up by or even independent of the insect, assisted in the feeding process. Yust and Fulton2 observed fluid exuding from broken-off mouth-parts left embedded in lemons after detachment of the coccids which had been feeding there. The exudate formed pools on the lemon skins from which samples were taken for sugar analyses. When experiments on the feeding preferences of Aphis fabae Scopoli3 were extended to the comparison of turgid and wilting leaves on otherwise similar plants, the wilting leaves proved to be less acceptable to the aphids. The inference that aphids depend less on their own sucking power than on the turgor pressure in the plant tissue, to maintain the flow of plant sap through the exceedingly fine food canal within their maxillary stylets, was checked by severing the mouth-parts of A. fabae individuals feeding on beans. Here, too, fluid was observed to exude from the stylet stumps left projecting from the plant surface.