Selection of Atriplex lentiformis Host Plants by Hesperopsis gracielae (Lepidoptera: Hesperiidae)

William D. Wiesenborn, Gordon F. Pratt

Abstract


We counted Hesperopsis gracielae (MacNeill) (Lepidoptera: Hesperiidae) eggs on Atriplex lentiformis (Torrey) S. Watson (Chenopodiaceae) plants on 3 dates during 2006-2007 next to the lower Colorado River in Cibola Valley, Arizona. The skipper has received conservation interest due to its restricted geographic range and apparent rarity. Atriplex lentiformis, the skipper’s only known host species, is a large shrub capable of C4 photosynthesis and N2 fixation. We measured the size (canopy radius) and percent water of plants and the percent nitrogen of leaves. Percentages of water and nitrogen were partially correlated, whereas plant size was not partially correlated with the percentage of water or nitrogen. Skipper eggs were more likely to be present on shrubs with greater canopy radius, water content, or nitrogen concentration. Likelihood of egg presence also increased with plant size when percent nitrogen was controlled and increased with percent nitrogen when plant size was controlled. Numbers of eggs, adjusted for canopy radius, on shrubs with at least 1 egg were not related to the percentage of water or nitrogen. Ovipositing H. gracielae appear to select host plants when thresholds of plant size and water or nitrogen content are exceeded. These plant characteristics should be considered when surveying or restoring the skipper’s habitat.

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