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Plagiometriona clavata

By Michael Leasia and Brian Scholtens

Geographic Range

Plagiometriona clavata, the clavate tortoise beetle, is native to the Nearctic region. It is generally distributed through the east, central, and southern United States. (Barney, et al., 2007; Ciegler, 2007; Riley, 1986)

Habitat

These leaf beetles are generally found on agricultural farms or suburban and urban gardens where solanaceous plants are grown. They can also be found sparsely in the wild where species of Solanum grow, usually in grasslands, meadows, and forests. (Riley, 1986)

Physical Description

Adults have large elytra and pronotum, creating a shield over the entire body. The head is covered by this shield when observed from the top. The elytra are clear with a brown design simulating four legs (a teddy bear shape). The elytra are tuberculate, have a post-scutellar protuberance, and the anterior elytral margins are crenulate. The venter of the pronotum does not have grooves. The tarsal claws are appendiculate. The antennae are long and narrow, with the 8th segments distinctly longer than wide. (Riley, 1986)

  • Sexual Dimorphism
  • sexes alike

Development

Development is typical for tortoise beetles. Eggs are laid on host plants, hatching several days later. The larva develops through about 5 to 6 instars before pupating, often on the host plant. (Chaboo, 2007; Riley, 1986)

Reproduction

Nothing is currently known about mating in this species.

It is assumed that mating in this species is similar to other known tortoise beetles. Adults mate and females lay eggs on the host plant. In the north, there is a single brood, but the species is multiple-brooded in the south. (Chaboo, 2007; Riley, 1986)

  • Breeding interval
    P. clavata breeds once per summer in the north and 2 or more times in the south.
  • Breeding season
    Breeding occurs during the spring and summer for this species.

Nothing is known about parental investment in this species. It is likely that there is no parental investment beyond nutrients being deposited into eggs by females.

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

The adult lifespan of this species has not been documented, but if typical of other tortoise beetles, it would be a few weeks in the summer. (Chaboo, 2007)

Behavior

The most intriguing behavior known of Plagiometriona clavata, as well as most tortoise beetles, is the production of a fecal shield by the larvae. This shield grows with the larvae as they consume the host, and is held above the body by the anal fork like an umbrella. Work from several studies have shown that these shields do not apparently conceal the larvae, but often do deter potential predators, such as true bugs, ants, beetles and spiders. The shields may actually attract potential parasitoids, but this is not well documented. (Chaboo, 2007; Nogueira-de-Sa and Trigo, 2002; Nogueira-de-Sa and Trigo, 2005; Olmstead and Denno, 1992; Olmstead and Denno, 1993; Vencl, et al., 1999; Vencl, et al., 2005; Vencl, et al., 2011)

Home Range

These beetles are primarily restricted to areas of host plant, and are not active fliers, although they have that capability. (Chaboo, 2007; Riley, 1986)

Communication and Perception

There has been little investigation of communication abilities, but it is known that the fecal shields of larvae emit chemical deterrents to some predators. Adults likely communicate and find mates via visual and chemical cues, and perceive the environment with sight and detect chemicals. (Nogueira-de-Sa and Trigo, 2002; Nogueira-de-Sa and Trigo, 2005; Olmstead and Denno, 1992; Olmstead and Denno, 1993; Vencl, et al., 1999; Vencl, et al., 2005; Vencl, et al., 2011)

Food Habits

Plagiometriona clavata feeds on several species of nightshade including Solanum dulcamara, S. americanum, S. carolinense, S. lycopersicum, S. pseudogracile, and S. tuberosum. Other solanaceous hosts include Capsicum sp., Datura wrightii, and D. stramonium. It eats the leaves of these plants. (Ciegler, 2007; Riley, 1986)

  • Plant Foods
  • leaves

Predation

Plagiometriona clavata is known to be preyed upon by ants, predatory Hemiptera, spiders and beetles as a larvae. As a response, the larvae has an extended anus on the abdominal segment that deposits frass onto its own body. This evidently does little to disguise larvae, but it does seem to repel potential predators by chemical cues. This defense mechanism uses the allelochemicals in their diet to create a chemical shield, partially warding off predators. (Nogueira-de-Sa and Trigo, 2002; Nogueira-de-Sa and Trigo, 2005; Olmstead and Denno, 1992; Olmstead and Denno, 1993; Vencl, et al., 1999; Vencl, et al., 2005; Vencl, et al., 2011)

Ecosystem Roles

Plagiometriona clavata feeds on many Solanum plants, as well as several other solanaceous plant species. However, it does not create enough damage to have an economic effect. It also serves as a prey item for several different Arthropod predators. (Chaboo, 2007; Ciegler, 2007; Nogueira-de-Sa and Trigo, 2002; Nogueira-de-Sa and Trigo, 2005; Olmstead and Denno, 1992; Olmstead and Denno, 1993; Vencl, et al., 1999; Vencl, et al., 2005; Vencl, et al., 2011)

Species Used as Host
  • Solanum dulcamara
  • Solanum americanum
  • Solanum carolinense
  • Solanum lycopersicum
  • Solanum pseudogracile
  • Solanum tuberosum
  • Capsicum sp.
  • Datura wrightii
  • Datura stramonium

Economic Importance for Humans: Positive

Plagiometriona clavata could possibly be studied and used as a chemical control for insect pests. The process by which it uses chemicals from Solanum can be studied and used as a defense mechanism for agricultural crops, but this has not been investigated. (Vencl, et al., 1999)

Economic Importance for Humans: Negative

Plagiometriona clavata has potential to evolve further to feed extensively on a larger variety of solanaceous plants, therefore becoming a pertinent agricultural pest.

  • Negative Impacts
  • crop pest

Conservation Status

This species has no current conservation status.

Contributors

Michael Leasia (author), University of Michigan Biological Station, Brian Scholtens (author, editor), University of Michigan Biological Station, Angela Miner (editor), Animal Diversity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

agricultural

living in landscapes dominated by human agriculture.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

diapause

a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Barney, R., S. Clark, E. Riley. 2007. Annotated list of the leaf beetles (Coleoptera: Chrysomelidae) of Kentucky: Subfamily Cassidinae. Journal of the Kentucky Academy of Sciences, 68: 132-144.

Chaboo, C. 2007. Biology and phlogeny of the Cassidinae Gyllenhal sensu lato (tortoise and leaf-mining beetles) (Coleoptera: Chrysomelidae). Bulletin of the American Museum of Natural History, 305: 1-250.

Ciegler, J. 2007. Leaf and seed beetles of South Carolina (Coleoptera: Chrysomelidae and Orsodacnidae). Biota of South Carolina. Vol. 5. Clemson, SC: Clemson University.

Flinte, V., D. Windsor, L. Sekerka, M. de Macedo, R. Monteiro. 2010. Plagiometriona emarcida (Boheman, 1855) and Plagiometriona forcipata (Boheman, 1855)(Coleoptera: Chrysomelidae: Cassidinae), a single species differing in larval performance and adult phenotype. Journal of Natural History, 44: 891-904.

Nogueira-de-Sa, F., J. 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: 203-206.

Nogueira-de-Sa, F., J. Trigo. 2005. Faecal shield of the tortoise beetle Plagiometriona aff. flavescens (Chrysomelidae: Cassidinae) as chemically mediated defence against predators. Journal of Tropical Ecology, 21: 189-194.

Olmstead, K., R. Denno. 1992. Cost of shield defense for tortoise beetles (Coleoptera, Chrysomelidae). Ecological Entomology, 17: 237-243.

Olmstead, K., R. Denno. 1993. Effectiveness of tortoise beetle larval shields against different predator species. Ecology, 74: 1394-1405.

Riley, E. 1986. Review of the tortoise beetle genera of the tribe Cassidini occurring in America north of Mexico (Coleoptera: Chrysomelidae: Cassidinae). Journal of the New York Entomological Society, 94: 98-114.

Vencl, F., F. Nogueira-de-Sa, B. Allen, D. Windsor, D. Futuyma. 2005. Dietary specialization influences the efficacy of larval tortoise beetle shield defenses. Oecologia, 145: 404-414.

Vencl, F., P. Trillo, R. Geeta. 2011. Functional interactions among tortoise beetle larval defenses reveal trait suites and escalation. Behavioral Ecology and Sociobiology, 65: 227-239.

Vencl, F., M. Morton, R. Mumma, J. Schultz. 1999. Shield defense of a larval tortoise beetle. Journal of Chemical Ecology, 25/3: 549-566.

Virkki, N., J. Santiago-Blay, E. Riley. 1992. Chromosomes of Puerto Rican Hispinae and Cassidinae (Coleoptera, Chrysomelidae). The Coleopterist's Bulletin, 46: 29-42.

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