Fecal shield

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Cassida viridis larva with fecal shield Cassida viridis Schildkafer (Chrysomelidae).P8193313 NEAT.jpg
Cassida viridis larva with fecal shield

The fecal shield is a structure formed by the larvae of many species of beetles in the leaf beetle family, Chrysomelidae. [1] [2] 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. [3] Other terms for the fecal shield noted in the literature include "larval clothing", "kotanhang" ("fecal appendage"), "faecal mask", "faecal pad", and "exuvio-faecal annex". [4]

Contents

Ecology

Beetle larvae of the chrysomelid subfamilies Criocerinae and Galerucinae retain their feces in piles on their backs, regularly adding material as feces slips off. The shields of Cassidinae larvae are generally mobile. They are built on paired caudal processes (also called urogomphi) to the posterior end of the body; these processes move the shield over the body like an umbrella. These shields may be raised and even swung to strike a predator. [5]

Cassida cf rubiginosa larva constructing the shield

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, [6] which is also known as the "anal fork". [7] The larva constructs the shield by maneuvering its "muscular telescopic and highly protrusible anus", [8] 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. [9]

The fecal shield takes many forms across species. In some, it covers the entire body, while in others it is narrower. [9] In some, it is simply a "clump". [4] In consistency it may be hard or rather "pasty". [9] 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. [5] Most fecal shields are bound with exuviae, the "skins" shed from the insect when it molts. [4] Some shields, such as that of Cassida stigmatica , are entirely frass-free, made only of exuviae. [10]

Function

The fecal shield is not just a physical barrier, but also a chemical one. When a larva feeds on a plant, it ingests secondary metabolites in the plant tissues, such as alkaloids, saponins, and phytol derivatives, and these are present in its feces. These chemicals can be a potent defense against predatory insects. For example, the larva of the tortoise beetle Plagiometriona clavata obtains chemical compounds from its diet of bittersweet ( Solanum dulcamara ), excretes them, and incorporates them into its shield, where they repel the predatory ant Formica subsericea . [11]

The fecal shield is beneficial, but it is not without its cost to the insect. Though it is made of waste products, the larva must exert energy simply to transport its weight. [3] A fecal shield can weigh half as much as the larva itself. [12] This energy might otherwise go into development. [3] The shield is also a problem for the larva when it has the opposite effect: its chemistry attracts predators instead of repelling them. Experiments with several larvae of genus Cassida that feed on volatile-rich tansy show that their shields attract the predatory ant Myrmica rubra . [10]

Another possible function of the fecal shield may include protection of the larva from environmental conditions such as ultraviolet radiation, desiccation, wind, and rain. [3]

See also

Camptosomata

Other leaf beetle larvae build a case made of waste materials. Examples are: Exema and Neochlamisus .

Related Research Articles

<span class="mw-page-title-main">Leaf beetle</span> Family of beetles

The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle families. Numerous subfamilies are recognized, but the precise taxonomy and systematics are likely to change with ongoing research.

<span class="mw-page-title-main">Frass</span> Waste from insects

Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter.

<span class="mw-page-title-main">Cryptocephalinae</span> Subfamily of beetles

The Cryptocephalinae are a subfamily of the leaf beetles (Chrysomelidae), and belong to the group of case-bearing leaf beetles called the Camptosomata. The cases are made from the feces of larvae, passed from one instar to the next, and ultimately serves as a pupation chamber.

<span class="mw-page-title-main">Cassidinae</span> Subfamily of beetles

The Cassidinae are a subfamily of the leaf beetles, or Chrysomelidae. The antennae arise close to each other and some members have the pronotal and elytral edges extended to the side and covering the legs so as to give them the common name of tortoise beetles. Some members, such as in the tribe Hispini, are notable for the spiny outgrowths to the pronotum and elytra.

<i>Charidotella sexpunctata</i> Species of beetle

Charidotella sexpunctata, the golden tortoise beetle, is a species of beetle in the leaf beetle family, Chrysomelidae. It is native to the Americas, and very broadly distributed. Charidotella sexpunctata was formerly known as Metriona bicolor. The species has also been seen in regions reaching up to Argentina.

<i>Cassida</i> Genus of beetles

Cassida is a large Old World genus of tortoise beetles in the subfamily Cassidinae. The natural history of Cassida sphaerula in South Africa is a typical life cycle. Several species of Cassida are important agricultural pests, in particular C. vittata and C. nebulosa on sugar beet and spinach. The thistle tortoise beetle has been used as a biological control agent against Canada thistle.

<span class="mw-page-title-main">Thistle tortoise beetle</span> Species of beetle

The thistle tortoise beetle is a species of beetle in the subfamily Cassidinae and the genus Cassida. The thistle tortoise beetle can be recognized by its green, rounded back and it can be found on thistle plants in many regions of North America and Europe. The thistle tortioise beetle was first discovered in 1902 in Lévis, Quebec. In 1931, Nellie F. Paterson was the first to document the mature larva. Later, the instar larva of this species was first recorded in 2004 by Jolanta Świętojańska. The thistle tortoise beetle exhibits multiple defense behaviors, such as a flexible shield, providing a barrier against the mandibles of predators, and an excretion that protects the eggs as well.

<i>Acromis spinifex</i> Species of beetle

Acromis spinifex is a species of tortoise beetle from South America. The males have enlarged elytra which are probably used in male–male combat, while females are among the few tortoise beetles to show maternal care of their offspring.

Insects have a wide variety of predators, including birds, reptiles, amphibians, mammals, carnivorous plants, and other arthropods. The great majority (80–99.99%) of individuals born do not survive to reproductive age, with perhaps 50% of this mortality rate attributed to predation. In order to deal with this ongoing escapist battle, insects have evolved a wide range of defense mechanisms. The only restraint on these adaptations is that their cost, in terms of time and energy, does not exceed the benefit that they provide to the organism. The further that a feature tips the balance towards beneficial, the more likely that selection will act upon the trait, passing it down to further generations. The opposite also holds true; defenses that are too costly will have a little chance of being passed down. Examples of defenses that have withstood the test of time include hiding, escape by flight or running, and firmly holding ground to fight as well as producing chemicals and social structures that help prevent predation.

<i>Blepharida rhois</i> Species of beetle

The sumac flea beetle, Blepharida rhois, is most commonly found in North America and is a member of the herbivorous beetle family, Chrysomelidae. More specifically, this beetle is part of the Alticinae subfamily, a highly diverse subfamily that includes more than 1000 species in 550 genera. Members of the Chrysomelidae family are distinguished by their enlarged metafemora and their ability to jump up to 100 times their length. This gives the beetle the ability to catapult jump in order to escape approaching predators. This ability has led to the common name of “flea beetle.” Both larvae and adults are typically a quarter of an inch long. While adults are cream colored with irregular reddish patterns, larvae are typically gray with yellow stripes.

<i>Deloyala guttata</i> Species of beetle

Deloyala guttata, the mottled tortoise beetle, is a species of tortoise beetle in the family Chrysomelidae. It is found in the Caribbean, Central America, North America, and South America.

<i>Hemisphaerota cyanea</i> Species of beetle

Hemisphaerota cyanea, also known as the Palmetto tortoise beetle, is a species in the Chrysomelidae family. Beetles in this family are commonly characterized by their small size, relatively oval and convex shape, variable color but often shining/ iridescent bodies, small heads, and 5-jointed tarsi. Other names include the Florida tortoise beetle and iridescent blue chrysomelid beetle. It is native to the southeastern United States. The specific name (cyanea) means "dark blue," and the beetle earned its name as the palmetto tortoise beetle because it is the only tortoise beetle that feeds on palms.

<i>Hemisphaerota</i> Genus of beetles

Hemisphaerota is a genus in the subfamily Cassidinae in the family Chrysomelidae. There are about 10 described species in Hemisphaerota.

<span class="mw-page-title-main">Hemisphaerotini</span> Tribe of beetles

Hemisphaerotini is a Neotropical tribe of tortoise beetles and hispines in the family Chrysomelidae. There are at least 2 genera and more than 40 described species in Hemisphaerotini.

<i>Calleida viridipennis</i> Species of ground beetle

The Calleida viridipennis is a species of ground beetle belonging to the Carabidae family, and are referred to as carabid beetles. It is found in various states, including New York, New Mexico, Louisiana, and Florida. Habitat preferences include forests and swamps. C. virdipennis is a particular carabid beetle that is, on average, 10 mm long. Recognizable by a green-black metallic exoskeleton, it has a trapezoidal head shape. Its large eyes are also characteristic of the species. Below the exoskeleton reside functional wings, giving the beetle flight capacity.

<i>Eurypepla calochroma</i> Species of beetle

Eurypepla calochroma, commonly known as the Geiger tortoise beetle, is a species of tortoise beetle. It is found in Florida, Central America and the Caribbean. This specific beetle only feeds on the Geiger tree throughout all of its life stages.

<i>Epistictina reicheana</i> Species of beetle

Epistictina reicheana, is a species of leaf beetle found in India, Nepal, Sri Lanka and Tasmania.

Laccoptera (Laccopteroidea) quatuordecimnotata, is a species of leaf beetle native to India, and Sri Lanka.

Silana farinosa, commonly known as curry-leaf tortoise beetle, is a species of leaf beetle native to Indo-China, India, Sri Lanka, Thailand and introduced to Peninsular Malaysia.

The Neotropical tortoise beetle tribe Spilophorini comprises two genera, Calyptocephala Chevrolat, 1836 and Spilophora Boheman, 1850. Biological information is limited but the life cycle includes six larval instars and the larvae construct a shield of their cast skins.

References

  1. ↑ 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.
  2. ↑ Chaboo, CS, Adam S, Nishida K, Schletzbaum L. 2023. Architecture, construction, retention, and repair of fecal shields in three tribes of tortoise beetles (Insecta: Coleoptera: Chrysomelidae Cassidinae: Cassidini, Mesomphaliini, Spilophorini). ZooKeys Special Issue, Research on Chrysomelidae 9. ZooKeys 1177: 87–146.
  3. 1 2 3 4 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.
  4. 1 2 3 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.
  5. 1 2 Chaboo, C. Defensive behaviors in leaf beetles: from the unusual to the weird. Archived 2013-12-07 at the Wayback Machine Pp. 59-69. In: Vivanco, J. and T. Weir (Eds.) Chemical Biology of the Tropics. Springer Verlag, Berlin. 2011.
  6. ↑ Gomes, P. A., et al. (2012). Biology of Omaspides pallidipennis Boheman, 1854 (Coleoptera: Chrysomelidae: Cassidinae). Psyche: A Journal of Entomology 2012 290102.
  7. ↑ Capinera, J. Golden Tortoise Beetle. Entomology and Nematology. University of Florida IFAS. 1997, revised 2012.
  8. ↑ Keefover-Ring, K. (2013). Making scents of defense: do fecal shields and herbivore-caused volatiles match host plant chemical profiles? [ permanent dead link ]Chemoecology 23(1) 1-11.
  9. 1 2 3 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.
  10. 1 2 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.
  11. ↑ Vencl, F. V., et al. (1999). Shield defense of a larval tortoise beetle. Journal of Chemical Ecology 25(3) 549-66.
  12. ↑ Mitton, J. Tortoise beetles and fecal shields. Colorado Arts and Sciences Magazine. College of Arts and Sciences. University of Colorado, Boulder. 2010.
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