Nature really is both amazing and horrific and always has the power to surprise me. I have been recording wildlife on my patch for 23 years and even after this time I am still discovering new things. In recent years feeling fairly secure on my bird, mammal, butterfly dragonfly and damselfly recording I have been trying to build up a list of what other invertebrates can be found.
Today I was out on my patch trying to count the clouds of
Banded Demoiselle damselflies, trying to get a picture of juvenile Great Tits, hoping
that the resident swans cygnets had hatched watching Perch in the mill race and
composing my next blogpost something had caught my eye.
I was planning on writing about the abundance of Scarce
Chasers on my patch. These dragonflies are… well scarce but seem to be doing
well on my patch where we seem to be on the northern edge of their range for
the river Avon. I was watching a male hunting over the meadow hoping to see it catch
something and then photography it with its prey when I noticed a strange fly or
wasp. It had an elongated white and black abdomen but fly like eyes. I took a
quick snap of the individual hoping to ID it later.
I finished my weekly survey and stopped at the local pub for
a soft drink and then had a look at the images I had taken. Superficially it
looked like a fly, not your average bluebottle or flesh fly, I mused as to whether
it was a solitary wasp, but no ovipositior and assumed it was one of the many thousand
species of fly, perhaps a robber fly? That would be interesting, robber flies
have an interesting ecology. Not having any books on flies and aware that my
insect books wouldn’t have too many flies in them, I opted for AI.
Artificial Intelligence and machine learning are powerful tools but with great power comes great responsibility and one must always understand the limitations and problems in their use. Any AI derived identification must be crosschecked with reliable sources. I use the Merlin Bird Song App, its great but occasionally throws up a strange species, if I am at all suspicious, I will only record that species if I then subsequently see it and confirm it.
The AI I used this time was Google Lens, a subscription image
search function of google that I had been using to ID plants and invertebrates.
I use it mainly to point me in the general direction, perhaps to the family or
genus level before diving deep into books or websites. In this case I uploaded
the image and waited whilst the wheels turned. Shortly it had an answer for me,
it had a few but number one was weird. It thought what I was looking at was a fungus.
It was clearly a fly; it was clearly wrong. So, I uploaded another image and
again it came up with a fungus. I did it to a third image and again the AI
model found for me a fungus.
It wasn’t just any fungus, it was the same fungus each time,
and the images it showed did look similar to my image, so I read a little
deeper. The fungus was Entomophthora muscae. Interesting the term muscae
relates in Latin to house flies. Entomophthora is also known as the Fly Death
Fungus and is a pathogenic fungus focused on various fly species. Fascinating.
I started to research a bit more and discovered that Entomophthora
have a unique life cycle. They require a fly host to live. Infectious spores
land on a fly and penetrate their skin and enter the flies basic blood system
known as haemolymph. Here the spores form cell-wall-less (protoplastic) cells
within the body cavity. They use up the body’s fats and other nutrients to
survive. Once it has drained the fly it has two options, if it was too quick
and the fly dies the cells turn into resting spores remaining in the decaying
carcass or if the fly is still alive it hijacks the fly causing its behaviour
to change. The fly will move to a higher position where the fungus produces a
mass of fruiting bodies called conidia that burst from between the segments of
the fly’s abdomen, hence the striking black and white markings I saw. These
conidia then spread spores that hopefully land on a passing fly and the
infection starts all over again.
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| See at bottom to reference to the paper this was taken from. |
On closer examination it was clear that the white parts of the abdomen were a non-fly related mass, and it was possible to see the fungal structures. The zombie nature of fungi is not unknown and is quite topical with the release of the second season of the Last of Us which revolves around a human infection of the Cordyceps fungus (something that Entomophthora does not do, it is only focused on flies). Cordyceps fungi infect a range of insects such as ants and control its behaviour to improve the chances of infecting another host. This turns its hosts into a kind of zombie unable to fight against the fungal mind control.
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Entomophthora promote a series of behaviours that is known as “summit disease”. The stricken fly immediately seeks elevated locations. If it is too weak to fly it will climb. At the top of a plant or object it will cease moving. Its legs will grip the surface. Its proboscis will extend, and a droplet of liquid will be exuded that sticks the fly to the surface ensuring it cannot be dislodged or fall. Next the wings will raise and spread out and its limbs will straighten; death usually occurs then. Secure and high the fungus now releases it spores that can then rain down on any flies beneath them. The full cycle lasts between 5-7 days
There are about 22 species of Entomophthora that infect 8 families of flies including Mosquitos, Hoverflies, House Flies, Fruit Flies and Flesh Flies. They are most active in May and June and September and October. So keep an eye out for Zombie flies being controlled by fungi.
For more information,
Carolyn Elya and Henrik H De Fine Licht (2021) The genus
Entomophthora: bringing the insect destroyers into the twenty-first century.
IMA Fungus 12 (1) DOI:10.1186/s43008-021-00084-w
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