Lepidopteran larvae in at least 14 taxonomically diverse families forcefully eject their fecal pellets (frass) great distances. This behavior often occurs in taxa that construct and inhabit leaf shelters. Larvae of Epargyreus clarus (Hesperiidae), the silver-spotted skipper, keep their leaf shelters entirely free of frass by ejecting their fecal pellets up to 40 times their body length away, and by removing pellets that are placed inside the shelter. Through experimental evaluations of the ecological significance of frass ejection and cleaning behavior I have determined that 1) E. clarus frass is attractive to a range of insects in the field, and that predatory wasps (Polistes fuscatus) are significantly more likely to locate and kill a larva in association with frass than one without frass; 2) larvae reared in continued contact with frass and its associated fungal colonists do not differ significantly in survival or time to pupation from those reared under clean conditions; and 3) repeated shelter construction does not affect larval growth rates, except when imposed at extremely high levels. Thus removal of cues for natural enemies is likely to have been an important selective force in the evolution of frass ejection behavior in shelter-dwelling larvae. Examination of defecation behaviors in an ecological context across a range of insects promises to reveal interesting and largely unexplored patterns.
Species 1: Lepidoptera Hesperiidae Epargyreus clarus (silver-spotted skipper)
Species 2: Hymenoptera Vespidae Polistes fuscatus (paper wasp)
Keywords: frass, defecation
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