Defensive Use of a "Fecal Shield" by a Beetle Larva

Eisner, Thomas; Tassell, Eileen van; Carrel, James E.

doi:10.1126/science.158.3807.1471

Cited by 71 publications

(82 citation statements)

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“…The list of enemies potentially deterred by the thatch must extend beyond the coccinellid larva and predaceous pentatomid tested by us. Ants must certainly constitute a hazard and might well be thwarted by the thatch, as they are by the fecal shield of other cassidines (1,5). It is noteworthy that, whereas the Hemisphaerota thatch appears to be pentatomid-proof, the shield of other cassidines offers only limited protection against heteropterans (2).…”

Section: Discussionmentioning

confidence: 99%

Defensive use of a fecal thatch by a beetle larva ( Hemisphaerota cyanea )

Eisner

2000

Proc. Natl. Acad. Sci. U.S.A.

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The larva of the tortoise beetle, Hemisphaerota cyanea (Chrysomelidae, Cassidinae), constructs a thatch from long filamentous fecal strands, beneath which it is totally concealed. The thatch is not discarded at molting but is enlarged by addition of strands as the larva grows. Thatch construction begins when the larva hatches from the egg. Pupation occurs beneath the thatch. Two predators, a coccinellid beetle larva (Cycloneda sanguinea) and a pentatomid bug (Stiretrus anchorago), were shown to be thwarted by the thatch. However, one predator, a carabid beetle (Calleida viridipennis), feeds on the larva by either forcing itself beneath the thatch or chewing its way into it. The attack behavior is stereotyped, suggesting that the beetle feeds on Hemisphaerota larvae as a matter of routine.Coleoptera ͉ Chrysomelidae ͉ Carabidae ͉ Calleida

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Section: Discussionmentioning

confidence: 99%

Defensive use of a fecal thatch by a beetle larva ( Hemisphaerota cyanea )

Eisner

2000

Proc. Natl. Acad. Sci. U.S.A.

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“…Larvae can carry masses of exuviae and feces that accumulate on a fork-like structure located on the last segment of the abdomen, forming a shield-like structure (Eisner & Eisner, 2000). Previous studies have demonstrated that the shield provides protection against various groups of predators (Eisner et al, 1967;Root & Messina, 1983;Olmstead & Denno, 1993;Vencl et al, 1999;Eisner & Eisner, 2000), but there are also cases in which fecal shields can serve as an attractive cue for generalist predators (Müller & Hilker, 1999). Several authors have shown that the protection is provided by chemical compounds found in the fecal shield (Gómez et al, 1999;.…”

Section: Introductionmentioning

confidence: 99%

Do fecal shields provide physical protection to larvae of the tortoise beetles Plagiometriona flavescens and Stolas chalybea against natural enemies?

Nogueira-de-Sá

Trigo

2002

Entomologia Exp Applicata

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During their larval phase, Plagiometriona flavescens (Boheman, 1855) and Stolas chalybea (Germar, 1824) (Chrysomelidae: Cassidinae), carry masses of feces and exuviae on their back called fecal shield, and it is suggested to protect larvae against natural enemies. We investigated if the physical barrier provided by the shield plays any role in the defense of these larvae. We conducted a field experiment checking the mortality of larvae of both species with their natural shields substituted by an artificial shield, with shields removed and with their shields intact. Mortality controls for each of the 3 shield treatments were carried out on host plants protected against natural enemies. On both species we observed that larvae with their shields intact had a significant lower mortality proportion than larvae with artificial shields or without shields. Control larvae on protected plants had low mortality. Our results agree with literature data, showing that fecal shields do not provide a physical protection to larvae but are important in their defense, probably due to the chemicals present in them.

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“…Tortoise beetles that vigorously wave their shields can beat back attacking predators (Eisner et al 1967;Go´mez 1997;Chaboo 2002;Mu¨ller 2002;Nogueira-de-Sa´and Trigo 2002); however, shields appear to be more than simple barriers. Chemical factors contribute to effective shield function in all our study species.…”

Section: Discussionmentioning

confidence: 99%

Dietary specialization influences the efficacy of larval tortoise beetle shield defenses

et al. 2005

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Plant chemical defenses and escape from natural enemies have been postulated to select for dietary specialization in herbivorous insects. In field and laboratory bioassays, we evaluated the effectiveness of intact and chemically modified larval shield defenses of the generalist Chelymorpha alternans and the specialists Acromis sparsa and Stolas plagiata (Chrysomelidae: Cassidinae) against three natural predators, using larvae reared on two morning glory (Convolvulaceae) species. We assessed whether: (1) specialists were better defended than generalists when both were fed and assayed on the same plant; (2) larval shield defenses were chemical, physical, or both; and (3) specialists exploit chemistry better than generalists. Live specialist larvae survived at higher rates than did generalists in predator bioassays with the bug Montina nigripes (Reduviidae), but there were no differences among groups against two species of Azteca ants (Hymenoptera: Dolichoderinae). Solvent leaching by H 2 O or MeOH significantly reduced shield efficacy for all species compared to larvae with intact shields. In contrast, freshly killed specialist larvae exhibited significantly lower capture rates and frequencies than the generalists. Although solvent leaching significantly reduced overall shield efficacy for freshly killed larvae of all species, the pattern of leaching effects differed between specialists and generalists, with H 2 O-leaching having a greater impact on the specialists. The overall vulnerability of the generalists appears due to lower chemical protection, which is ameliorated by increased escape behaviors, suggesting a selective trade-off between these defensive components. These experiments indicate that shield defenses are essential for larval survival and that specialists are superior at exploiting plant compounds residing in the aqueous fraction. Our results support the hypothesis that diet-specialized herbivorous insects have more effective defenses than generalists when both feed on the same plant due to the differential ability to exploit defensive precursors obtained from the host. The evolution of dietary specialization may therefore confer the advantage of enhanced enemy-free space.

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Defensive Use of a "Fecal Shield" by a Beetle Larva

Abstract: The larva of Cassida rubiginosa carries a tight packet of cast skins and feces on a fork held over its back. The packet is a maneuverable shield used by the larva to protect itself against attack. It is highly effective in blocking the bite of ants.

Cited by 71 publications

References 1 publication

Defensive use of a fecal thatch by a beetle larva ( Hemisphaerota cyanea )

Defensive use of a fecal thatch by a beetle larva ( Hemisphaerota cyanea )

Do fecal shields provide physical protection to larvae of the tortoise beetles Plagiometriona flavescens and Stolas chalybea against natural enemies?

Dietary specialization influences the efficacy of larval tortoise beetle shield defenses

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