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Bombylius

By Deena Hauze

Diversity

Bombylius, commonly known as bee-flies, is a genus that includes 3 subgenera and an estimated 335 subspecies worldwide. Bee-flies are mimics of bumblebees and other unrelated bees. Larvae are parasitoids that feed on the eggs, larvae, and stored pollen of solitary bees. Bee-flies are important pollinators. (Evenhuis and Greathead, 1999; "Genus Bombylius", 2012; Roskov, et al., 2020)

Geographic Range

Bee flies are nearly worldwide in distribution. There are approximately 280 subspecies in the United States. Large bee-flies are the most common species of the genus and are found across the northern hemisphere. There have been 23 subspecies recorded in the Ethiopian, 150 in the Palearctic, 109 in the Nearctic, 12 in the Neotropical, and 11 in the Oriental regions. (Evenhuis and Greathead, 1999)

Habitat

Bee-flies are found in warm regions where flowering plants live. They can be seen on the ground, near flowers, and in bushes during the day. At night, they shelter in the crowns of trees. (Kastinger and Weber, 2001)

Physical Description

Bee-flies are a genus that imitates various bees, such as bumblebees. Similarly to bumblebees, bee-flies are densely hairy with body colorings ranging from black to orange. The hairs are often a lighter color than the body, except one subspecies that is covered with black hair. Unlike bees, bee-flies have a long proboscis, four long legs, short antennae, and two wings. They do not have a stinger. Bee-flies are medium-sized, but subspecies vary in size from 8-16 mm. The females of some subspecies are larger than the males. Larvae look like grubs. (Kastinger and Weber, 2001; Moisset, 2020)

  • Sexual Dimorphism
  • female larger

Development

Eggs are laid individually at the entrances of solitary bee nests. The eggs hatch and the larvae seek out and feed upon stored pollen, bee eggs, and bee larvae. Once the larvae are grown, they pupate and remain in the bee nest until the next spring. (Kastinger and Weber, 2001)

Reproduction

Bee-flies mate and lay eggs during the spring to early summer. After mating, they seek out the nests of solitary bees to lay eggs. Once a nest has been found, the female hovers over the entrance and drops an individual egg. This process repeats. The eggs hatch, feed, pupate, then wait for the next spring to arrive. The larvae are parasitic. (Kastinger and Weber, 2001; Riley, 1881)

No information about parental involvement for this genus was found. (Kastinger and Weber, 2001)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Little information is available on the lifespan of bee-flies due to their high mobility. The lifespan has been determined to be greater than two weeks because eggs appear at the earliest two weeks after adults. Bee-flies are found during spring to early summer. (Evenhuis and Greathead, 1999)

Behavior

Bee-flies are a genus of solitary flies. They make a buzzing sound when flying, are very fast flyers, and are able to hover in mid-air. (Kastinger and Weber, 2001)

Members of the genus are most active during the day when the weather is sunny and warm. They are typically found on the ground and flying in forests and bushes. When the weather is cloudy, bee-flies will sit on the ground in an attempt to warm themselves. If the sun reappears, the bee-flies will start to fly again. At night, they avoid the ground and bushes, as they seem to hide in the crowns of trees. (Kastinger and Weber, 2001)

Communication and Perception

Bee-flies use the sense of sight, touch, sound, and chemical receptors to get information and communicate. (Kastinger and Weber, 2001; Moisset, 2020)

Food Habits

Adults feed primarily on nectar. Pollen has been found in the systems of adults, but it is unknown if it was eaten intentionally. Larvae are parasitoids that feed on the eggs, larvae, and stored pollen of host bees. (Kastinger and Weber, 2001; Moisset, 2020)

Predation

Bee-flies are mimics of bumblebees (Bombus species). ("Genus Bombylius", 2012; Kastinger and Weber, 2001)

  • Anti-predator Adaptations
  • mimic

Ecosystem Roles

Adults are pollinators of a large variety of flowers. Larvae are parasitoids of bees and feed on bee larvae. Instead of bees, the larvae of some species are parasitic to the eggs and larvae of locusts, fly pupa, and caterpillars. (Evenhuis and Greathead, 1999; "Genus Bombylius", 2012; Riley, 1881)

Species Used as Host

Economic Importance for Humans: Positive

Bee-flies are important pollinators. They visit purple, violet, blue, and white flowers more often than other colors. Lungwort, purple gromwell, common bugloss, and European stickseed are commonly visited plants. (Kastinger and Weber, 2001)

  • Positive Impacts
  • pollinates crops

Economic Importance for Humans: Negative

There are no known adverse effects of bee-flies on humans. (Kastinger and Weber, 2001)

Conservation Status

No special status.

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Deena Hauze (author), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

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

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

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

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

forest

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

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.

nectarivore

an animal that mainly eats nectar from flowers

nomadic

generally wanders from place to place, usually within a well-defined range.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

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

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

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

solitary

lives alone

tactile

uses touch to communicate

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

2012. "Genus Bombylius" (On-line). Bug Guide. Accessed May 08, 2020 at https://bugguide.net/node/view/9490#synonyms.

Beal, F. 1912. Food of our more important flycatchers. U.S. Department of Agriculture, Biological Survey Bulletin, 44.

Evenhuis, N., D. Greathead. 1999. World Catalog of Bee Flies (Diptera: Bombyliidae). Leiden: Backhuys Publishers. Accessed May 08, 2020 at http://hbs.bishopmuseum.org/bombcat/.

Kastinger, C., A. Weber. 2001. Bee-flies (Bombylius spp., Bombyliidae, Diptera) and the pollination of flowers. Flora, 196: 3-25.

Moisset, B. 2020. "Bee Flies (Bombylius spp.)" (On-line). U.S. FOREST SERVICE. Accessed May 08, 2020 at https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/bee_flies.shtml.

Riley, . 1881. The American Naturalist. Larval Habits of Bee-Flies, 15(6): 438-447.

Roskov, Y., G. Ower, T. Orrell, D. Nicolson, N. Bailly, P. Kirk, T. Bourgoin, R. DeWalt, W. Decock, E. van Nieukerken, L. Penev. 2020. "Species 2000 & ITIS Catalogue of Life" (On-line). Accessed May 09, 2020 at www.catalogueoflife.org/col.

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