Visitation of Heliotrope and Western Purslane Flowers by Hesperopsis gracielae (Lepidoptera: Hesperiidae)

William D. Wiesenborn, Gordon F. Pratt

Abstract


We conducted 2 studies on nectar-feeding by MacNeill's sootywing, Hesperopsis gracielae (MacNeill), a rare skipper, near the lower Colorado River in Cibola Valley, Arizona. In the first study, we examined rates of visitation by adults to Heliotropium curassavicum (Boraginaceae) inflorescences and Sesuvium verrucosum (Aizoaceae) flowers on potted plants. Visitation rates per plant or per inflorescence or flower did not differ between species when species were placed alone or together or when plants were placed in sun or shade. Frequencies of landings on both species were greater on plants in sun than shade, suggesting sooty-wings visually respond to flowers when foraging for nectar. In the second study, we measured masses of sugar in H. curassavicum inflorescences on wild plants after visitation by male or female adults. Inflorescences visited by females contained more sugar, but similar numbers of flowers, than those visited by males. Amounts of sugar remaining in inflorescences visited by females, but not males, decreased as visitation-times increased. Ingestion of nectar was apparent only in females. Both plant species can provide H. gracielae adults with nectar in conserved or created habitat.

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