In June I was down on the Sussex coast at the mouth of the river Cuckmere. During a bioblitz event I was supporting I discovered something I never expected to see. At the foot of either the first or seventh of the Seven Sisters cliffs, the fenceline and surrounding grasslands were alive with invertebrates. One large thistle plant was covered in all kinds of insects. I felt especially drawn to a beautiful orange and black ichneumon wasp clambering over the spiny leaves. But there was something else that caught my eye.
I noticed a dead fly in a quite unnatural position, a bit like an upside down koala. It was clamped onto one of the spines in a way that reminded me of the famous victims of the parasitic ‘zombie fungus’ cordyceps. Luckily I had my macro lens with me and could get a close-up of the fly.
The body looked an unusual shade for this species and, looking closer, you could see it was kind of mouldy. I showed everyone I could, taking away the images and several questions I needed to answer for myself!
That afternoon I put the photos on Twitter and had a quick reply from Lukas Large, a known fungi expert in the UK. He said it was a species of entomophthora, a group of fungi that kill flies, just as this one had done. It does much more than that beforehand, however.
Somehow, the fungus enters a final stage of mummification where it ‘gains control’ of the fly’s brain and therefore control over its functions. The fungus is then able to make the fly move to a high position in order to disperse its spores from the dead fly. That is mind blowing in more ways than one.
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