Instar-Specific Morphometrics and Linear Discriminant Models for Age-Grading Field Populations of Acyrthosiphon kondoi (Homoptera: Aphididae)

Abstract

Reliable criteria for age-grading field-collected Acyrthosiphon kondoi Shinji are of critical importance for proper development and interpretations of time-specific life table data. Classification criteria in the form of linear discriminant models were developed for laboratory populations of A. kondoi using measurements of several body structures. These models were further validated using field-collected aphids from 11 locations across Oklahoma over a period of 2 yr. Despite greater variability and generally larger size of aphids in field populations, linear discriminant models provided highly accurate (>99%) criteria for identifying all instars. Misclassification was observed only in the first instar, where 0.9% of nymphs were classified as second instars. To attain this degree of accuracy in classifying individuals from field populations, lengths of cornicles, first flagellar segments, and fore tibiae are required.