Apocephalus borealis

Apocephalus borealis
Adult female A. borealis next to grains of sugar for size comparison, note the ovipositor
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Diptera
Family:	Phoridae
Tribe:	Metopininae
Genus:	Apocephalus
Species:	A. borealis
Binomial name
Apocephalus borealis Brues, 1924[1]

Apocephalus borealis is a species of North American parasitoid phorid fly that parasitizes bumblebees, honey bees, and paper wasps. These flies are colloquially known as zombie flies and the bees they infect are colloquially known as zombees.^[2] The association with honey bees has so far only been documented from California, South Dakota, Oregon, Washington, and British Columbia (Vancouver Island);^[3] elsewhere, they are primarily associated with bumblebees and paper wasps, but most recently this species has changed host and has begun to attack the European honey bee. A case was confirmed in October 2013 of an infestation of honeybees in Vermont.^[4]

History

The infection of European honey bees in North America by A. borealis was first discovered by Dr. John Hafernik, who noticed disoriented honey bees at a light at night on San Francisco State University's campus. He picked some up in a vial, forgot about them, and about a week later noticed that fly larvae had emerged from the dead bees.^[5] Information is insufficient as to why the parasitic fly jumped to its new host, but concern exists that this new host provides an opportunity for the fly to thrive and further threaten the decreasing honey bee population.^[6] A. borealis has been suggested as a possible vector promoting the spread of the pathogens responsible for colony collapse disorder.^[7][8]

Lifecycle

Female flies lay their eggs in the bees, and as the larvae develop, they attack the bees' brains and cause them to become disoriented. Infected bees can be found walking in circles, as well as losing the ability to stand. The honey bees also remain inactive during the daytime until death occurs. The infected bees are also known to fly at night and exhibit other unusual behaviors such as hive abandonment in unusual weather conditions such as cold, rainy nights when most insects remain inactive.^[9] These behaviors eventually result in the death of the bees, but increase the survival and spread of the phorid flies. Female phorid flies immediately attack honey bees when put together. Females attack and pursue host honey bees until they land on their abdomens and insert the ovipositor for about two to four seconds, injecting eggs. Development of larvae takes an average of a week; the larvae feed on the honey bees' muscles and nervous system. Mature fly larvae typically emerge from the host between the head and thorax (but rarely result in decapitation), and pupate outside the host body. About 28 days are needed for the entire lifecycle to take place.^[7]

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  Ovipositor of an A. borealis

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  Female A. borealis ovipositing eggs into the abdomen of a worker honey bee

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  Two final-instar larvae of A. borealis exiting a honey bee worker at the junction of the head and thorax

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  Adult female A. borealis

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  Head of an A. borealis

The initial description of the species by Charles Thomas Brues, 1924.^[1]

Zombee Watch

A citizen project, "Zombee Watch", now uses a social media framework for people to report sightings of potentially parasitized bees.^[5] The stated goals of the project are to determine where in North America the zombie fly is parasitizing honey bees, how often honey bees leave their hives at night (even if they are not parasitized), and to engage citizen scientists in making a significant contribution to knowledge about honey bees and to become better observers of nature.^[10]

References

Wikimedia Commons has media related to Apocephalus borealis.

External links

• ZomBee Watch is a citizen science project sponsored by the San Francisco State University Department of Biology, the San Francisco State University Center for Computing for Life Sciences and the Natural History Museum of LA County.