LARVAL INSTAR DETERMINATION AND TEMPERATURE‐DEVELOPMENT STUDIES OF IMMATURE STAGES OF THE COMMON ARMYWORM, MYTHIMNA CONVECTA (WALKER) (LEPIDOPTERA: NOCTUIDAE)

Abstract

Larvae of the common armyworm, Mythimna convecta had 6 or 7 instars when reared on artificial diet at 25°C. Instars could be clearly separated on the basis of head capsule widths, but larval growth did not follow “Dyar's Rule”. Seven instar larvae lived longer and yielded heavier pupae than 6 instar larvae. The developmental periods of eggs, larvae and pupae were measured over a range of temperatures between 10°C to 35°C. Both Pradhan's and Stinner's equations provided a better fit to the observed values than thermal summation. In Victoria, M. convecta would have more generations/year but lower winter survival than the southern armyworm, Persectania ewingii (Westwood). Copyright © 1984, Wiley Blackwell. All rights reserved