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Agasicles hygrophila

By Sarah Knight

Geographic Range

The alligatorweed flea beetle naturally inhabits southern Brazil and northern Argentina along waterways. It has been introduced to the southern United States. (Jackman, 2003; Weeden, et al., 1996)

Habitat

The alligatorweed flea Beetle is naturally restricted to waterways where the plant Alternanthera philoxeroides (the alligator weed) grows. Agasicles hygrophila require a steady temperature of 20 - 30 degrees Celsius. (Jackman, 2003; Jolivet and Cox, 1996a; Jolivet and Hawkeswood, 1995; Weeden, et al., 1996)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Adult beetles are between 4 and 7 mm long, and about 2 mm wide . Head and thorax are shiny and black in color. Adult elytra (forwings) are characterized by black and yellow longitudinal stripes, and they also have greatly enlarged hind femora for jumping. Mature larvae are up to 6 mm long and are black. Eggs are cream colored at deposition and gradually become yellowish (or pale orange-yellow) in color. (Center, et al., 1998; Weeden, et al., 1996; White, 1983)

Reproduction

Females lay eggs 6 days after emergence. Females may lay up to 1000 eggs, and they deposit the eggs in masses on the undersides of alligatorweed leaves. The eggs are arranged in 2 parallel rows to form a zigzag pattern. Eggs hatch after 4 days (at diurnal temperatures between 20-30°C with sustained high humidity, while the larval stage generally lasts 8 days. Pupation takes place in the hollow stem of the plant. (Center, et al., 1998; Jolivet and Cox, 1996a; Jolivet and Cox, 1996b; Weeden, et al., 1996)

  • Range eggs per season
    1000 (high)

Food Habits

Agasicles hygrophila feeds on alligator weeed (Alternanthea philoxeroides) almost exclusively, but will occaisonally feed on Polygonaceae, which is a closely related plant family to alligator weed. Adults feed on young foliage, while larvae feed on stems and eat the lower surface of the leaves (they also prefer young leaves). (Center, et al., 1998; Jolivet and Cox, 1996a)

  • Plant Foods
  • leaves
  • wood, bark, or stems

Economic Importance for Humans: Positive

Agasicles hygrophila are important as a biological control agent of alligator weed. Alligator weed is an invasive exotic plant to North America, New Zealand, Australia, and several Asian countries. It became an invasive by being transported in the ballast water of ships from South America. It grows in dense mats that crowd out native vegetation and block the passage of light through the water. These mats interfere with the function of the invaded habitat, navigation, recreation, flood control, and rice production.

Agasicles hygrophila is used in the biological control of Alligatorweed because it is the primary consumer of Alligatorweed. In Florida, introduced populations of A. hygrophila were so effective in controlling Alligatorweed that 3 years after its introduction the U.S. Army Corps of Engineers canceled all herbicide sprays of the plant. (Jolivet and Cox, 1996a; Jolivet and Cox, 1996b)

  • Positive Impacts
  • controls pest population

Conservation Status

Contributors

Sara Diamond (editor), Animal Diversity Web.

Sarah Knight (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

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

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

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.

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.

freshwater

mainly lives in water that is not salty.

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

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

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.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sexual

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

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

References

Center, T., A. Dray, V. Vandiver. 1998. "The Alligatorweed Flea Beetle.” Facts Sheet AGR 80: University of Florida Cooperative Extension Service: Institute of Food and Agricultural Sciences." (On-line). Accessed March 3, 2001 at http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_AG011.

Jackman, J. 2003. "Alligatorweed Flea Beetle" (On-line). Biological Control of Weeds in Texas. Accessed 01/25/05 at http://bc4weeds.tamu.edu/agents/alligatorweedfleabeetle.html.

Jolivet, P., M. Cox. 1996. Chrysomelidae Biology: Volume 1 The Classification, Phylogeny, and Genetics. New York: SPB Academic Publishing.

Jolivet, P., M. Cox. 1996. Chrysomelidae Biology: Volume 2 Ecological Studies. New York: SPB Academic Publishing.

Jolivet, P., T. Hawkeswood. 1995. Host Plants of the Chrysomelidae of the World. Leiden, the Netherlands: Backhuys Publishers.

Weeden, C., A. Shelton, M. Hoffman. 1996. "Agasicles Hygrophila" (On-line). Accessed March 3, 2001 at http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/agasicles.html.

White, R. 1983. A Field Guide to the Beetles of North America. New York: Houghton Mifflin Company.

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