Adult dogbane beetles are iridescent blue-green beetles with copper-colored shine on their front wings. The legs and antennae are really dark blue that is almost black. Their heads and upper parts of their bodies have small, deep holes. They have long antennae between their eyes that have 12 joints each. Their front mouthparts, called mandibles, are flat and adapted to eating plants. The left side is longer, and actually fits into a groove on the right. Their mouthparts are also adapted to lapping up juice from milkweed plants. Dogbane beelte larvae have white bodies and brown heads. (Blatchely, 1926; Wilson, 1934)
Dogbane beetles are found wherever the plants they live on are found. Most often, they feed and live on dogbane plants, especially Indian hemp and spreading dogbane. Indian hemp is found throughout the entire United States and is often thought of as a weed. It prefers open habitats where it can spread. It lives along the side of roads, fields, railroad tracks, lakeshores, and places that have been disturbed. Spreading dogbane is found in the northeastern United States. Spreading dogbane lives in forests, at the edge of forests, along the banks of streams, and in fields with sand or gravel soil. (Dobler and Farrell, 1999; Peterson, et al., 2001; Schultz and Burnside, 1979; Wilson, 1934)
Larvae in the first stage of development, or first instar, hatch from eggs in midsummer. They burrow into the soil and eat the roots of the plant they live on. They develop in a chamber in the soil, and wait for their bodies to harden before they dig their way back up to the surface. Adult dogbane beetles mate and lay eggs during the rest of the summer. (Peterson, et al., 2005)
Dogbane beetles mate about once a day, usually early in the day. Males search for and choose females to mate with. After mating, males ride on the backs of the females to guard them. Dogbane beetles have more than one mate. In the West, dogbane beetles sometimes mate and cross with cobalt milkweed beetles. The mixed beetles are blue-green to brown-purple, but are not able to reproduce. (Peterson, et al., 2001; Peterson, et al., 2005; Schwartz and Peterson, 2006)
Dogbane beetles lay eggs on leaves and stems of the plants where they live or on nearby plants. They lay eggs in large groups of cases, called capsules, that are usually 3 mm wide by 2 mm tall. (Peterson, et al., 2005; Zabriskie, 1895)
Female dogbane beetles lay eggs in capsules, which are cases that protect them. The eggs are left on plants to develop and hatch by themselves.
Adult dogbane beetles emerge in early summer and live as adults for 6 to 8 weeks. (Peterson, et al., 2005)
Dogbane beetles live in small groups in different places because they cannot travel very far and are not very good at colonizing new places. (Williams, 1992)
Dogbane beetles move between plants within a particular area of plants it lives on.
Leaf beetles use visual, chemical, and scent information about their environment when moving into their host plant. Dogbane leaf beetles use chemical signals to communicate with each other in mating. The chemicals are specific to dogbane leaf beetles, and make it less likely that they would mate with other beetles like cobalt milkweed beetles. (Fernandez and Hilker, 2007; Peterson, et al., 2007)
Dogbane beetles mostly eat dogbane plants, usually Indian hemp and spreading dogbane. They also eat milkweed. To protect themselves from being eaten, dogbane plants give off a milky liquid that dries and makes the mouthparts of insects sticky. Dogbane beetles eat the outside parts of the leaves that have less latex and also rub it off on the leaves. They leave sticky bits of latex on dogbane plants. Dogbane beetle larvae mostly eat the roots of the same plants. (Peterson, et al., 2001)
Dogbane plants that dogbane beetles eat have contain chemicals called cardenolides, which partially protect them from diseases and animals. Cardenolides are bitter and toxic to insects. However, many insects that eat plants have adapted to be able to consume and store these chemicals in their bodies. If the beetle is bothered, it releases the chemicals, which puts off predators. Larvae that have a lot of these chemicals are not bothered as much by parasitic wasps. (Dobler, et al., 1998; Dobler, et al., 2011; Labeyrie and Dobler, 2003)
There are no known negative economic impacts of dogbane beetles on humans.
There are no known positive economic impacts of dogbane beetles on humans.
Dogbane beetles are not endangered.
Jaclyn Tolchin (author), University of Michigan Biological Station, Catherine Kent (editor), Special Projects.
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.