QUANTIFICATION OF ELECTROANTENNOGRAM RESPONSES OF THE PRIMARY RHINARIA OF ACYRTHOSIPHON-PISUM (HARRIS) TO C4-C8 PRIMARY ALCOHOLS AND ALDEHYDES

Electroantennograms (EAGs) of the distal and proximal primary rhinaria (DPR and PPR, respectively) were recorded from excised antennae of al ate virginoparous pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae). Primary unsaturated alcohols and aldehydes with varying c arbon length (C4-C-8) were used as volatile stimuli. EAGs were recorde d for a series of source concentrations from the DPR and PPR separatel y through the use of sectional electroantennography. A logistic equati on was fitted to the source concentration-response data. Differences i n relative EAG response of the DPR and PPR to the alcohols and aldehyd es were analyzed by deriving five parameters from this logistic equati on. These parameters relate to particular characteristics of sigmoid c urves: the saturation (maximum) EAG response (R(s)), the concentration for which the relative EAG response is 1/2R(s) (CR50), the stimulus r esponse range (SR0.9), the threshold concentration (CR1), and the EAG response area (A(R)). Of these parameters, the EAG response area showe d the largest separation between EAG responses of the DPR and PPR to t he two homologous groups and between compounds with varying carbon cha in lengths. The DPR was significantly more responsive to alcohols than to aldehydes, while the reverse was true for the PPR, indicating a ba sic difference between the two primary rhinaria. The highest overall r esponses were elicited by 1-hexanol, hexanal, and heptanal.