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Bolitotherus cornutus

By Evelyne Orlander

Geographic Range

The horned fungus beetle, also known as the forked fungus beetle, can be found in the northeastern part of United States and eastern part of Canada. (Milne and Milne, 1980)

Habitat

These beetles live in dying and dead tree trunks found in forest habitats. (Evans and Bellamy, 1996; Whitlock, May, 1992)

Physical Description

The color of horned fungus beetles ranges from black to a dark brown. There is a distinct sexual dimorphism. While both males and females have antennae, males have two horn-shaped antennae that extend forward on the head and one forked horn on the middle of the head. Females have tubercles on the heads and a heavy plate on the back at the abdominal tip. Adults are about 8 to 12 millimeters long and have wings. They have front wings that are hardened and hind wings that are membranous. (Conner, July, 1988; Milne and Milne, 1980)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    8 to 12 mm
    0.31 to 0.47 in

Development

There are three stages in the development of Bolitotherus cornutus. First, the eggs are deposited in or on fungi. Next, larvae develop feeding on fungal tissues. About three months later larvae pupate, emerging as adults in late summer or in early spring after hibernating throughout the winter. (Conner, July, 1988; Milne and Milne, 1980)

Reproduction

During courtship a male climbs on the back of a female, twitches its body, and then it strokes the female’s head with its feet. Males with a bigger horn have a competitive advantage over other males during courtship. Though it appears that the females have no control over which male becomes interested in them, they do get to decide which male can transfer a spermatophore. The heavy plates on the female's back will open to allow the transfer of spermatophore under the voluntary power of the female only. The male then guards the female for two to five hours after courtship. (Bartalon and Brown, 1986; Conner, July, 1988)

Females copulate aproximately every nine days, and lay at least one egg per insemination. Female horned fungus beetles are very particular in selecting where they lay their eggs. The size of the larval host determines the survival of the larvae as well as the size of the horn in male offspring. (Conner, July, 1988)

  • Breeding season
    June- August
  • Range eggs per season
    1 (low)

Lifespan/Longevity

Adult beetles may live up to five years. (Evans and Bellamy, 1996)

  • Typical lifespan
    Status: wild
    5 (high) years

Behavior

A slow-moving organism, the horned fungus beetle stays within a small area. Males become aggressive towards one another during courtship, while females lack horns and do not demonstrate any aggressive behavior. If disturbed, the beetle will feign death and remain motionless as it blends in with the rotting wood around it. Though the beetle has wings, it flies only in the rare instance of migration to another area of fungus. The beetle usually stays in the same fungus covered log from hatching til death. (Conner, July, 1988; Lundrigan, 1997; Milne and Milne, 1980; Whitlock, May, 1992)

Food Habits

These beetles and the larvae are saprophagous. They eat fungus off of dying or dead trees.

  • Other Foods
  • fungus

Predation

There are few predators of this beetle. (Conner, July, 1988)

  • Anti-predator Adaptations
  • cryptic

Conservation Status

Contributors

Sara Diamond (editor), Animal Diversity Web.

Evelyne Orlander (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

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

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.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

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.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

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.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

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

terrestrial

Living on the ground.

References

Bartalon, J., L. Brown. 1986. Behavioral Correlates of Male Morphology in a Horned Beetle. American Naturalist, Vol. 127, No. 4.: 565-570.

Conner, J. July, 1988. Field Measurements of Natural and Sexual Selection in the Fungus Beetle, *Bolitotherus cornutus*. Evolution, Vol. 42, No. 4: 736-749.

Evans, A., C. Bellamy. 1996. An Inordinate Fondness for Beetles. New York: Henry Holt and Company.

Kickx, J. 2003. "White Spongy Trunk Rot" (On-line). Accessed October 6, 2001 at http://www.pfc.forestry.ca/diseases/CTD/Group/Heart/heart3_e.html.

Lundrigan, T. 1997. "Movement Rates as an Indicator of Dispersal Potential in the Forked Fungus Beetle, *Bolitotherus cornutus*" (On-line). Accessed October 3, 2001 at http://ace.acadiau.ca/science/biol/honours/biofeedback97/Lundrigan.html.

Milne, L., M. Milne. 1980. The Audubon Society Field Guide to North American Insect and Spiders. New York: University of New Hampshire.

Whitlock, M. May, 1992. Nonequilibrium Population Structure in Forked Fungus Beetles: Extinction, Colonization, and the Genetic Variance Among Populations. American Naturalist, Vol. 139, No. 5: 952-970.

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