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CORNICLE LENGTH AS A CRITERION FOR SEPARATING FIELD-COLLECTED NYMPHAL INSTARS OF THE PEA APHID, ACYRTHOSIPHON PISUM (HOMOPTERA: APHIDIDAE)

Published online by Cambridge University Press:  31 May 2012

William D. Hutchison
Affiliation:
Department of Entomology, University of Wisconsin, Madison 53706
David B. Hogg
Affiliation:
Department of Entomology, University of Wisconsin, Madison 53706

Abstract

Cornicle length measuremetns of Acyrthosiphon pisum (Harris) nymphs reared in the laboratory were instar-specific and unaffected by rearing temperature. A multimodal analysis of cornicle lengths of field-collected aphids clearly detected four distribution peaks (i.e., instars) in five different field populations, and there was generaaly little overlap between successive instar distributions. However, third and fourth instars in the spring field sample could not be separated accurately due to the shorter cornicle length of nymphs that developed from overwintered eggs. Cornicle length proved to be a useful criterion for separating virginoparous A. pisum instars in samples collected in southern Wisconsin.

Résumé

La longueur des cornicules chez des larvs de Acyrthosiphon pisum (Harris) élevées au laboratoire est caractéristique du stade et n'est pas affectée par la températrre d'élevage. Une analyse multimodale de la longueur des cornicules chez des individus provenant du terrain a révélé des distributions præsentant clairement 4 modes (les stades) chez 5 populations différentes, et peu de chevauchement est apparu entre les distributions des différents stades. Cependant, les stades trois et quatre n'ont pu être séparés précisément pour les populations printannières du terrain, dû à la longueur réduite des cornicules chez les larves provenant des oeufs d'hivernement. La longueur des cornicules s'est avérée un critère utile pour sæparer les stades des virginopares de A. pisum dans des échantillons recueillis au sud du Wisconsin.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1983

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