Chrysochus auratus    

common name     Dogbane Beetle

Species occupies habitat where host plants are found, and range from riparian to agricultural areas. Often found in open, disturbed areas, or along forest edges, lakeshores, and areas with gravelly soil. (Dobler & Farrel 1999 and Peterson et al. 2001).

Adults emerge from underground in early summer, and are present during the remaining summer months. The Strickland Museum specimens indicate that C. auratus is common into late summer, as many specimens were collected between June and August.

6.8-11.3 mm in length. Vivid metallic golden green in colour, with green abdominal sterna (Peterson et al. 2001). Antennae and legs are dark blue in colour, and antennae are filiform and 12-jointed. The mandibles are adapted for herbivory, and the left is longer than the right. The left mandible rests inside a groove on the right (Wilson 1934).

life history
Along with C. colbaltinus, C. auratus is the only North American representative of the genus (Peterson et al. 2001). Their host plants provide them with chemical compounds called cardenolides, which are used for predator defense (Dobler & Farrell 1999). Species exhibit little sexual dimorphism. They produce a single generation per year. First instar larvae hatch in midsummer, and burrow into the soil, where they pupate. The average lifespan is approximately 6 to 8 weeks. They mate once per day during their lifespan, usually early in the day, and males engage in post-copulatory mate guarding, which can last for 1.5 hours. They have been found to engage in interspecific copulation with C. colbaltinus, producing viable offspring with unique behaviour and phenotype, although hybrids tend to be sterile (Peterson et al. 2001).

Nothing indicating that the species is rare or threatened. Within its range, it is commonly reported.

diet info
Species feeds on dogbane plants, Apocynaceae (Dobler & Farrell 1999). The larvae are obligate root feeders, and adults eat the leaves of larval host plants (Peterson et al. 2001). Species has been reported to feed on milkweed plants, but research with food choice trials has indicated that many individuals will only feed on dogbane species (Dobler & Farrell 1999).

Found across the United States, from southern Canada to New Mexico (Dobler & Farrell 1999), east of the Rocky Mountains. In Utah and Arizona, species can be found extending west into the Rocky Mountains (Peterson et al. 2001). In Canada, species can be found in eastern Alberta, and southern Saskatchewan. Specimens from the Strickland Museum have been collected from the Medicine Hat area, New Jersey, and Chicago.

This species is often the focus of studies on evolution, dispersal, speciation, and feeding and mating behaviours due to its interesting life history (Peterson et al. 2001). They also lay their eggs in what appear to be droppings. Even after hatching, the larvae will usually spend some time underneath the dark dirt-like covering (Wilson 1934).

species page authorCampbell, E.2013 

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