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fecal shield
The fecal shield is a structure formed by the larvae of many species of beetles in the leaf beetle family, Chrysomelidae.〔Nogueira-de-Sá, F. and J. R. Trigo. (2002). (Do fecal shields provide physical protection to larvae of the tortoise beetles ''Plagiometriona flavescens'' and ''Stolas chalybea'' against natural enemies? ) ''Entomologia Experimentalis et Applicata'' 104(1) 203-06.〕 It is composed of the frass of the insect and often its exuviae, or bits of shed exoskeleton. The beetle may carry the shield on its back or wield it upon its posterior end. The main function of the fecal shield is defense against predators.〔Bacher, S. and S. Luder. (2005). (Picky predators and the function of the faecal shield of a cassidine larva. ) ''Functional Ecology'' 19(2) 263–72.〕 Other terms for the fecal shield noted in the literature include "larval clothing", "''kotanhang''" ("fecal appendage"), "faecal mask", "faecal pad", and "exuvio-faecal annex".〔
==Ecology==
Beetle larvae of the chrysomelid subfamilies Criocerinae and Galerucinae often wear their fecal shields in piles on their backs, regularly adding material as bits chip off. The shields of Cassidinae larvae are mobile. They are attached to the posterior end of the body and moved into position as needed, sometimes held in place above the larva like an umbrella. They may be raised and even swung to strike a predator.〔Chaboo, C. (Defensive behaviors in leaf beetles: from the unusual to the weird. ) Pp. 59-69. ''In:'' Vivanco, J. and T. Weir (Eds.) ''Chemical Biology of the Tropics''. Springer Verlag, Berlin. 2011.〕
When the shield is carried on the tip of the abdomen, it is secured to a double-lobed, spine-like process called the caudal furca,〔Gomes, P. A., et al. (2012). (Biology of ''Omaspides pallidipennis'' Boheman, 1854 (Coleoptera: Chrysomelidae: Cassidinae). ) ''Psyche: A Journal of Entomology'' 2012 290102.〕 which is also known as the "anal fork".〔Capinera, J. (Golden Tortoise Beetle. ) Entomology and Nematology. University of Florida IFAS. 1997, revised 2012.〕 The larva constructs the shield by maneuvering its "muscular telescopic and highly protrusible anus",〔Keefover-Ring, K. (2013). (Making scents of defense: do fecal shields and herbivore-caused volatiles match host plant chemical profiles? ) ''Chemoecology'' 23(1) 1-11.〕 or "anal turret", which is positioned dorsally, on the back. It excretes an amount of feces, sometimes with a droplet of gluey secretion, and places it on the caudal furca using its anal turret. In the species ''Hemisphaerota cyanea'', the larva constructs a shield which may be more descriptively called a "fecal thatch", because it is woven from narrow, coiled strands of frass. The larva begins feeding immediately upon emergence from the egg and within minutes it produces its first fecal strand. Within twelve hours, its thatch-shield is full-sized. The larva diligently repairs the shield with replacement strands when it is broken.〔Eisner, T. and M. Eisner. (2000). (Defensive use of a fecal thatch by a beetle larva (''Hemisphaerota cyanea''). ) ''Proceedings of the National Academy of Sciences'' 97(6) 2632-36.〕
The fecal shield takes many forms across species. In some, it covers the entire body, while in others it is narrower.〔 In some, it is simply a "clump".〔Gómez, N. E., et al. (1999). (Chemical defense in larval tortoise beetles: essential oil composition of fecal shields of ''Eurypedus nigrosignata'' and foliage of its host plant, ''Cordia curassavica''. ) ''Journal of Chemical Ecology'' 25(5) 1007-27.〕 In consistency it may be hard or rather "pasty".〔 In some species of the subfamily Chrysomelinae, the female adult coats each of her eggs with feces, and when the larva emerges, it uses this ready-made fecal casing as the base of its shield, adding to it as it grows. These casings tend to be quite hard, and have been compared to adobe.〔 Most fecal shields are bound with exuviae, the "skins" shed from the insect when it molts.〔 Some shields, such as that of ''Cassida stigmatica'', are entirely frass-free, made only of exuviae.〔Müller, C. and M. Hilker. (1999). (Unexpected reactions of a generalist predator towards defensive devices of cassidine larvae (Coleoptera, Chrysomelidae). ) ''Oecologia'' 118(2) 166-72.〕
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