Dietary Effect of Ecdysone and 20-Hydroxyecdysone on Larval Development of Two Lepidopteran Species

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Abstract
The sweet potato hornworm, Agrius convolvuli and the cabbage armyworm, Mamestra brassicae were reared from hatching on artificial diets supplemented with ecdysone or 20-hydroxyecdysone. The effects of the two ecdysteroids on larval development were investigated. In A. convolvuli, an extra larval molt was induced by 400 ppm ecdysone and a maximum of 4 additional larval ecdyses were induced by 800 ppm ecdysone. Conversely, 20-hydroxyecdysone did not affect larval development although much larger amounts of 20-hydroxyecdysone were present in the hemolymph than was found in the hemolymph of larvae fed ecdysone. In M brassicae, neither ecdysone nor 20-hydroxyecdysone affected larval development. Although larvae were fed on large amounts of ecdysteroids, the ecdysteroid level in the hemolymph remained as low as that in control larvae. These results suggest that ecdysone, but not 20-hydroxyecdysone, can induce multiple additional larval ecdyses in A. convolvuli, as it does in Bombyx mori, but that the sensitivities to ingested ecdysteroids differ widely among the species.