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.
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.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- savanna or grassland
- forest
- scrub forest
- Other Habitat Features
- suburban
- agricultural
- riparian
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.
- Other Physical Features
- ectothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
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.
- Development - Life Cycle
- metamorphosis
- diapause
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.
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.
- Mating System
- polygynandrous (promiscuous)
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.
- Key Reproductive Features
- seasonal breeding
- sexual
- fertilization
- oviparous
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.
Behavior
Due to limited dispersal ability, dogbane beeltes live in small, sporadic populations.
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.
- Other Communication Modes
- pheromones
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.
- 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.
- Anti-predator Adaptations
- aposematic
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
).
- 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.
Additional Links
Contributors
Jaclyn Tolchin (author), University of Michigan Biological Station, Catherine Kent (editor), Special Projects, Brian Scholtens (editor), University of Michigan Biological Station.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- scrub forest
-
scrub forests develop in areas that experience dry seasons.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- 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.
- 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.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- fossorial
-
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- visual
-
uses sight to communicate
- chemical
-
uses smells or other chemicals to communicate
- pheromones
-
chemicals released into air or water that are detected by and responded to by other animals of the same species
- visual
-
uses sight to communicate
- chemical
-
uses smells or other chemicals to communicate
- 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.
- herbivore
-
An animal that eats mainly plants or parts of plants.
- folivore
-
an animal that mainly eats leaves.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- 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.
References
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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.
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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.
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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 .