Larvae of the silver-spotted skipper, Epargyreus clarus (Hesperiidae), construct shelters from leaves of their leguminous host plants, making four distinct shelter types that change predictably over larval ontogeny. Shelters built by first-instar larvae are located on the apical half of the leaflet and are almost invariant in size, shape, and orientation, suggesting a stereotypical process of shelter location and construction. We have determined that the regularity of these shelters results from a prescribed pattern of larval movements and behaviors, in which larvae use their body length as a "ruler" and employ silk not only as a building material but also as a template to guide the location of cuts in the leaf. Though lepidopteran larvae lack the sensitive antennae, long jointed appendages, and other measurement devices used by structure-building bees, wasps, and caddis flies, they can nonetheless use simple tools and behavioral patterns to produce characteristic and regular shelters.
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We are grateful to Sharon Komarow for capable assistance in the field and lab and to John McClure for assistance with preparation of the figures. Mike Singer, Elizabeth Bernays, John McClure, Megan Brooks, Erin Wilson, Eliza Beardslee, and two anonymous reviewers provided useful comments on the manuscript. USDA NRI Grant 97-35311-5151 and the Washington Biologists’ Field Club provided financial support.