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Chrysochus auratus

By Jaclyn Tolchin

Geographic Range

Dogbane beetles live in the Nearctic Region throughout the eastern United States and southern Canada. The western boundaries of its range are the Rocky Mountains, Utah, and Arizona. (Blatchely, 1926; Peterson, et al., 2001)

Habitat

Dogbane beetles are found in areas where host plants live. They feed and live mainly on dogbane plants (Apocynaceae), especially Indian hemp (Apocynum cannabinum) and spreading dogbane (A. androsaemifolium). Indian hemp, often regarded as a weed, can be found throughout the entire United States in various soil types. It prefers open habitats where it can spread, such as roadsides, fields, railroad tracks, lakeshores, and disturbed areas. Spreading dogbane is found in the northeastern United States. This plant also spreads easily and can survive in a number of habitats. It prefers forests, forest edges, streambanks, and fields with sandy or gravelly soils. (Dobler and Farrell, 1999; Peterson, et al., 2001; Schultz and Burnside, 1979; Wilson, 1934)

Physical Description

Adult dogbane beetles are distinctly colored, iridescent blue-green chrysomelids with elytra that have a copper shine. The antennae and legs are a bluish-black. The head and thorax have sporadic punctures that are deep and minute. They have long, 12-jointed, filiform antennae that are located between the eyes and frontal ridge. The mandibles are blunt and built for a herbivorous diet. The left is longer than the right and fits into a groove in the right. Their large hypopharynx is thought to be an adaptation to lapping the juice of milkweed plants. Larvae have a white body and brown head. (Blatchely, 1926; Wilson, 1934)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    8 to 11 mm
    0.31 to 0.43 in

Development

First instar larvae hatch from eggs in midsummer and burrow into the soil where they feed externally on host plant roots. Larvae pupate in a chamber in the soil, where they remain until their bodies harden enough to burrow up to the surface in early summer. Adults mate and lay eggs throughout the rest of the summer after emergence. (Peterson, et al., 2005)

Reproduction

Dogbane beetle males and females mate an average of once per day during their lifetime, taking multiple mates. Males actively search out and choose females to mate with; female choice is ineffective. The entire mating process usually lasts over an hour and a half due to postcopulatory mate guarding, where males ride on the females backs after insemination in order to ensure that the female uses his sperm to fertilize her eggs. Mating usually takes place early in the day. (Peterson, et al., 2001; Peterson, et al., 2005; Schwartz and Peterson, 2006)

Interspecies mating has been observed between dogbane beetles and cobalt milkweed beetles (Chrysochus cobaltinus) toward the western boundary of the dogbane beetle range. Viable hybrid offspring are produced. In areas where both species are present, hybrids make up 10-15% of the total combined populations. Hybrid offspring have an intermediate morphology; they range from blue-green in color to brown-purple with brown abdominal sterna, which contrasts with the shiny green of dogbane beetles and blue of cobalt milkweed beetles. As adults, F1 offspring mate as frequently as non-hybrids, but they cannot reproduce. Dogbane beetle males are generally less choosy than cobalt milkweed beetles. For those that live in the hybrid zone, however, males of both species are usually more choosy. (Peterson, et al., 2001; Peterson, et al., 2005; Schwartz and Peterson, 2006)

Dogbane beetles lay eggs on leaves and stems of host plants and nearby vegetation in masses of egg capsules. The capsules are usually 3 mm wide by 2 mm tall. (Peterson, et al., 2005; Zabriskie, 1895)

  • Breeding interval
    Dogbane beetles produce one generation each year.
  • Breeding season
    Adults mate from mid to late summer.

No information is available on parental care. Females provision eggs, which are left on plants to mature on their own.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

After adults emerge in early summer, they spend their 6 to 8 week lifespan on host plants, mating an average of once per day. (Peterson, et al., 2005)

  • Typical lifespan
    Status: wild
    42 to 56 days

Behavior

Due to limited dispersal ability, dogbane beeltes live in small, sporadic populations. (Williams, 1992)

Home Range

Dogbane beetles can move from plant to plant within an area of host plants.

Communication and Perception

Leaf beetles in the Chrysomelid family use visual, olfactory and chemical cues when colonizing a host plant. Dogbane leaf beetles in particular use chemical signaling systems in mating. Cuticular hydrocarbon (CHC) signals serve as sex pheromones. CHCs are sex-specific and species-specific and influence male dogbane beetles in mate choice. It is thought that the species-specific aspect of these pheromones suggests that evolutionary forces are selecting against interspecific mating. (Fernandez and Hilker, 2007; Peterson, et al., 2007)

Food Habits

Dogbane beetles feed mainly on dogbane plants (Apocynaceae), specifically Indian hemp (Apocynum cannabinum) and spreading dogbane (Apocynaceae androsaemifolium). They are also known to feed on milkweed (Asclepiadaceae). To deter herbivores, dogbane plants expel a milky latex that dries and sticks to mouthparts of other insects. Dogbane beetles do not cut leaf veins prior to feeding like many herbivorous insects. They feed on the low-latex tissue of the distal part of leaves. After feeding and accumulating latex on mouthparts, dogbane beetles place their mouthparts on the leaf and walk backward in order to rub the latex off. Walking backward prevents the insect from walking through the latex smear and accumulating latex on its feet. Latex bands of approximately 2 mm in width and 2 cm in length have been observed on dogbane plants. Dogbane beetle larvae feed on the roots of the host plants. (Peterson, et al., 2001; Williams, 1992; Wilson, 1934)

  • Plant Foods
  • leaves
  • roots and tubers
  • flowers

Predation

Dogbane plants (Apocynaceae) eaten by dogbane beetles contain cardenolides, which deter pathogens and herbivores. Cardenolides are bitter and toxic to insects. However, many herbivorous insects, such as dogbane beetles, have developed adaptations that allow them to ingest and sequester the toxin. Dogbane beetles can use the compounds as a defense mechanism against predators in the same way that plants do. When the beetle is disturbed, cardenolides released through glands on the pronotum and elytra deter predation. Larvae that have high concentrations of the toxin are parasitized less frequently by parasitic wasps. (Dobler, et al., 1998; Dobler, et al., 2011; Labeyrie and Dobler, 2003)

Ecosystem Roles

Dogbane beetles eat and live on dogbane plants (Apocynaceae), specifically Indian hemp (Apocynum cannabinum) and spreading dogbane (A. androsaemifolium). They also occasionally live and feed on milkweed plants (Asclepiadaceae). (Peterson, et al., 2001; Williams, 1992; Wilson, 1934)

Species Used as Host
  • dogbanes (Apocynum cannabinum)
  • Indian hemp (Apocynum cannabinum)
  • spreading dogbane (Apocynum androsaemifolium)
  • milkweed (Asclepiadaceae)

Economic Importance for Humans: Positive

There are no known positive economic impacts of dogbane beetles on humans.

Economic Importance for Humans: Negative

There are no known negative economic impacts of dogbane beetles on humans.

Conservation Status

Dogbane beetles are not known to be endangered. Their conservation status is not evaluated by the IUCN Red List of Threatened Species.

Contributors

Jaclyn Tolchin (author), University of Michigan Biological Station, Catherine Kent (editor), Special Projects, Brian Scholtens (editor), University of Michigan Biological Station.

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.

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.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

herbivore

An animal that eats mainly plants or parts of plants.

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.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

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

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.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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.

visual

uses sight to communicate

References

Blatchely, W. 1926. Catalogue of the Coleoptera of Indiana. Indianapolis, Indiana: WM. B. Burford, Contractor for State Publishing and Printing.

Dobler, S., D. Daloze, J. Pasteels. 1998. Sequestration of plant compounds in a leaf beetle’s defensive secretion: cardenolides in Chrysochus. Chemoecology, 8: 111-118.

Dobler, S., B. Farrell. 1999. Host use evolution in Chrysochus milkweed beetles: evidence from behaviour, population genetics and phylogeny. Molecular Ecology, 8: 1297–1307.

Dobler, S., G. Petschenka, H. Pankoke. 2011. Coping with toxic plant compounds – The insect’s perspective on iridoid glycosides and cardenolides. Phytochemistry, 72: 1593–1604.

Fernandez, P., M. Hilker. 2007. Host plant location by Chrysomelidae. Basic and Applied Ecology, 8: 97-116.

Labeyrie, E., S. Dobler. 2003. Molecular Adaptation of Chrysochus Leaf Beetles to Toxic Compounds in Their Food Plants. Molecular Biology and Evolution, 21: 218-221.

Peterson, M., S. Dobler, J. Holland, L. Tantalo, S. Locke. 2001. Behavioral, molecular and morphological evidence for a hybrid zone between Chrysochus auratus and C. cobaltinus (Coleoptera: Chrysomelidae). Annals of the Entomological Society of America, 94: 1-9.

Peterson, M., S. Dobler, E. Larson, D. Juarez, T. Schlarbaum, K. Monsen, F. Wittko. 2007. Profiles of cuticular hydrocarbons mediate male mate choice and sexual isolation between hybridising Chrysochus (Coleoptera: Chrysomelidae). Chemoecology, 17: 87-96.

Peterson, M., E. Larson, M. Brassil, K. Buckingham, D. Juarez, J. Deas, D. Manglona, M. White, J. Maslan, A. Schweitzer, K. Monsen. 2011. Cryptic gametic interactions confer both conspecific and heterospecific advantages in the Chrysochus (Coleoptera: Chrysomelidae) hybrid zone. Genetica, 139: 663-676.

Peterson, M., K. Monsen, H. Pedersen, T. McFarland, J. Bearden. 2005. Direct and indirect analysis of the fitness of Chrysochus (Coleoptera: Chrysomelidae) hybrids.. Biological Journal of the Linnean Society, 84: 273-286.

Schultz, M., O. Burnside. 1979. Distribution, Competition, and Phenology of Hemp Dogbane (Apocynum cannabinum) in Nebraska. Weed Science, 27: 565-570.

Schwartz, S., M. Peterson. 2006. Strong material benefits and no longevity costs of multiple mating in an extremely polyandrous leaf beetle, Chrysochus cobaltinus (Coleoptera: Chrysomelidae). Behavioral Ecology, 17: 1004-1010.

Williams, C. 1991. Host plant latex and the feeding behavior of Chrysochus auratus (Coleoptera: Chrysomelidae). The Coleopterists Bulletin, 45: 195-196.

Williams, C. 1992. Movement of the Dogbane Beetle, Chrysochus aura/us (Coleoptera: Chrysomelidae), in a Patchy Environment. Banisteria, 1: 8-10.

Wilson, S. 1934. The anatomy of Chrysochus auratus, Fab., Coleoptera: (Chrysomelidae) with an extended discussion on the wing venation. Journal of the New York Entomological Society, 42: 65-85.

Zabriskie, J. 1895. Egg-capsules of Chrysochus auratus (Fab.). Journal of the New York Entomological Society, 3: 192. Accessed July 25, 2012 at http://www.jstor.org.proxy.lib.umich.edu/stable/10.2307/25002685?origin=api.

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