Lack of Translation of Density-Induced Morphological Polyphenism to Long-Duration Flight Behavior of Black Cutworm (Lepidoptera: Noctuidae)

Abstract

Larvae of black cutworm, Agrotis ipsilon (Hufnagel), reared under crowded conditions in the laboratory were darker and developed more slowly than larvae reared singly. Crowding reduced the length and weight of pupae, and the adults were correspondingly smaller than those from uncrowded populations. Rate of reproductive maturation of females was not influenced by larval density. Crowding had no significant effect on the crawling behavior of sixth instars and very little effect on the flight behavior of adults tethered to flight mills. No evidence that crowding leads to a distinct migratory phase or even to an increased propensity to initiate long-duration flight was found. To the contrary, the data suggest that moths from crowded populations may suffer a loss in migratory capacity because of their smaller size (and presumably smaller stores of flight fuel) and lower wing area:body size ratios, which may make flight energetically more expensive.