beetle horn, and we illustrate how each of these mechanisms could contribute to the above trajectories of horn evolution.
Beetle horns form as long tubes, localized regions of epidermal tissue that undergo a burst of proliferation at the end of the larval period, just before pupation (Fig. 14.6) (Emlen and Nijhout, 1999). As these horn cells proliferate, they fold in on themselves to produce a compact disc of epidermal tissue that unfurls to its full length during the pupal molt. In these respects, beetle horns develop in a way very similar to the traditional appendages in beetles and other insects (e.g., wings or legs), and it now appears that similar mechanisms may be involved.
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14 On the Origin and Evolutionary Diversification of Beetle Horns--DOUGLAS J. EMLEN, LAURA CORLEY LAVINE, and BEN EWEN-CAMPEN ."
In the Light of Evolution: Volume 1. Adaptation and Complex Design . Washington, DC: The National Academies Press,
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