What's That Bug? does not endorse extermination

Luciia Clusters
Location: Nova Scotia
November 8, 2010 3:19 pm
My friend snapped this photo of slow-moving flies in clusters on a tomato plant on an August, ”fairly humid” day in Canada (I didn’t know Canada had warmth or humidity). They must be Lucilia (seracata?), but what are they doing?
Signature: Mel the Bug Chaser

Mysterious Fly Deaths

Hi Mel,
We are familiar with single Flies being overcome by a fungus infestation (see BugGuide), but this group cemetery is a bit of a mystery that alas, we cannot immediately research as we have already spent far too much time at the computer this morning and we must attend to a few things before leaving home to teach California college students.  Perhaps there will be a comment or two on this posting when we return.

Eric Eaton Concurs
Daniel:
I’m betting it is still fungus-related, but the bottom line is I have no idea.  Maybe the person took images a few hours (or a day or two) later, and then the fungal spores would have been visible?
Eric

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What's That Bug? does not endorse extermination
Location: Canada

3 Responses to Mysterious Fly Deaths

  1. After researching earlier today about insects being infected by fungus I did come across something that might apply here. I read about how fungus that effects ants can take out entire colonies because as the fungus reaches it’s final stages, it shoots out spores in every direction that will infect any nearby ants. Because of this, ants that become infected are quickly banished and removed from the colony.

    Now…whether that relates to this situation or not is debatable, but perhaps that’s the situation here? One infected fly, wasp, caterpillar reached it’s final fungal stage and shot out spores infecting a group of flies. Granted, it would take some time before the fungus overtook the flies and made them imobile, they could have congregated together during this stage. Fungus is also said to control the minds of their insect hosts, so possibly the fungus controlled the flies to cause them to congregate so that the fungus could grow together?

    All of this is speculation based on what I read earlier, but if this is a fungus infection, perhaps this is a possible cause?

  2. Dave says:

    Though it’s likely fungal, applying an ant-based theory is difficult because the flies aren’t part of a colony; each one would be attracted to a smell or a visual cue, and land to investigate.

    Maybe that’s what happened here, but it’s odd that their bodies seem to be aligned in the same direction. There’s no randomness that one would expect due to individual flies coming in from various directions and getting stuck.

  3. Kevin Brown says:

    It is very strange due to the habits flys have and the way they are positioned. Initially I thought it could be the plant itself but then they would be all over the place in different directions. I still think a cordycep could be responsible especially since it could have affected the flys in a larval phase when they were in the same lain area.

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