Shoo Fly, Don’t Bother Bee!!!


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Could this tiny fly be responsible for the disappearing honeybees? Image courtesy of the Public Library of Science

In my previous article on Colony Collapse Disorder (CCD) in honeybees, I summarized recent advances in our understanding of this malady which has arisen in recent years, leading to major declines in honeybee colonies throughout North America.

The current consensus is that CCD is caused by a synergistic combination of internal (diseases, parasites) and extrinsic (pesticides, climate change) factors that stress bees to the point that the population of the hive eventually collapses under these pressures.

Colony Collapse Disorder

One curious aspect of Colony Collapse Disorder (CCD) is that most bees do not die within or near the hive.  Instead, they simply fly away, never to be seen again.

A team of researchers based at San Francisco State University presented another potential piece in the CCD puzzle that might help explain this unusual hive abandonment behavior.

Core et al. (2012) announced the discovery of a fly that parasitizes honeybees.  Taken by itself, it may seem like an unremarkable discovery of yet another parasite of honeybees (and there are many).

But what makes this fly, Apocephalus borealis Brues, different from other parasites is that its larvae alter the behavior of the bee, leading them to fly off to forage at night rather than during the day.  Although A. borealis has previously been found parasitizing paper wasps, bumble bees, fireflies and even spiders, it had never been documented attacking honeybees until now.

Apocephalus borealis

Apocephalus borealis is a member of a group of species within the family Phoridae that have collectively been termed the “decapitating” flies.  They are so named because of the unusual behavior of the larvae to develop inside the head.  Decapitating flies have been relatively well-documented in ants, and some related phorid species in the genus Pseudacteon are being evaluated as a possible biological control agent because they attack imported fire ants.

While the host is alive, the activity of the larvae causes various behavioral symptoms like disorientation, walking in circles, and loss of limb control.  When the larvae are ready to pupate, they burst through the membrane between the head and the thorax of their host (not unlike in the Alien movie series), causing the head of the host to fall off.

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