Dead Hoverflies Mystery

[Sienna]

I was in my garden a couple of years ago, insect spotting, and happened to come across a large number of hoverflies. Great! I thought, so I got my camera out to take a few pictures. It was at this point I realised that none of them were moving: all were dead. There were about twenty altogether and all were on Ribwort Plantain in various natural positions (as shown below) in a very small area of the garden.

There were no sources of pesticides anywhere around as I had done my best to ensure my garden was specifically for wildlife.

I thought it was unusual to find so many dead all at the same time in such a small area but for all I know this could be part of the natural life-cycle (and if it is, I apologise ). Everyone I have asked so far has had no explanation for it so I thought I’d give it a shot and post it here.









Any ideas?

Sienna

[Jason Green]

Hi Sienna,

They've been killed by a fungus, such as Entomophthora. See related thread: Fungus on Dung-fly?

Take care,

Jason

[Sienna]

Originally Posted by Jason Green

Hi Sienna,

They've been killed by a fungus, such as Entomophthora. See related thread: Fungus on Dung-fly?

Thanks for the link Fascinating read.

You said, at one point, on that particular thread:

The infection apparently seems to influence their destination - as they're about to die, they climb up a grass blade or similar and open their wings to aid the escaping spores to exit as they release in the wind.

now that is amazing

How does the infection induce the insect to do that?

Thanks again,

Sienna

[Rossco]

The fungi is a body-snatcher - it takes over the fly's central nervous system. There are loads examples of internal parasites modulating the behaviour of their hosts to ensure they complete their own life cycle. Particularly grisly examples are Leucochloridium paradoxum, Sacculina spp. and Nematomorph worms.

Take a look at them on the web.

[Sienna]

Hello Rossco,

Sorry I am a bit late in replying but was working all day yesterday and fell straight into bed at the end of it all.

The fungi is a body-snatcher - it takes over the fly's central nervous system. There are loads examples of internal parasites modulating the behaviour of their hosts to ensure they complete their own life cycle. Particularly grisly examples are Leucochloridium paradoxum, Sacculina spp. and Nematomorph worms.

Take a look at them on the web.

Had a look at the parasites you suggested......amazing. I had absolutely no idea that they could do that. You have opened up whole new realms for me to explore. Thank you

When looking up Nematomorph Worms I came across a video which I’ve linked to below:

YouTube - Nematomorph worm

During the video it is said : “....it is the parasite’s genes that are being expressed in the behavioral phenotype of the infected host and instructs it to jump”. Does something similar happen with the parasitic fungi or do they control the host in a different way?

Thanks again,

Sienna

[Rossco]

Hello Sienna

For anything to be controlled with such fine precision, the parasite must somehow get its own genes expressed in the host. How the parasites I mentioned before do this I don't know, but there are some parasites that package their genes into polydnaviruses, which are injected into the host cells. These insert the parasite's DNA and overcome its defences. Take a look at the link below for a fascinating example of how certain parasitic wasps overcome the immune system of their host:

Polydnavirus - Wikipedia, the free encyclopedia

It's a wiki link, but accurate. Still, you may want to trawl the web for more information. Also check out the microsporidians, Wolbachia bacteria and the protozoa, Toxoplasma gondii, the pathogen that causes toxoplasmosis. All of these monkey about with their hosts in some incredible ways. If you read a lot about Toxoplasma gondii it may make you feel differently about cats.

What we know about this sort of stuff is really the tip of the iceberg. I'd wager that any organism that lives on, or more specifically in, another organism must change the host to suit itself. These relationships have evolved over tens or hundreds of millions of years, so there must be some crazy things going on.

Ross

[Rossco]

Also, along the lines of what you saw with the hoverflies, take a look at the pictures below from Brazil. They show hemipteran bugs that have been parasitized by a Cordyceps fungi. The really long threads are the fruiting bodies of the fungi and like your hoverflies, the fungi has made the insect climb up high and cling on to distribute the spores.

Check these out too:
Perilitus coccinellae - some threads and pics on here a while ago about this wasp
Ampulex compressa

These are parasitic wasps, but here, venom is important in host behaviour modulation.

[Sienna]

Hello Ross,

For anything to be controlled with such fine precision, the parasite must somehow get its own genes expressed in the host. How the parasites I mentioned before do this I don't know, but there are some parasites that package their genes into polydnaviruses, which are injected into the host cells. These insert the parasite's DNA and overcome its defences.

Of course, I hadn’t thought of that before. It’s all quite phenomenal, isn’t it?

Do you know of any good books on parasite-host relationships that you could recommend?

Take a look at the link below for a fascinating example of how certain parasitic wasps overcome the immune system of their host:

Polydnavirus - Wikipedia, the free encyclopedia

It's a wiki link, but accurate. Still, you may want to trawl the web for more information.

Amazing.

Now I’ve never heard about a wasp with a symbiotic relationship with a virus before.

Also check out the microsporidians, Wolbachia bacteria and the protozoa, Toxoplasma gondii, the pathogen that causes toxoplasmosis. All of these monkey about with their hosts in some incredible ways. If you read a lot about Toxoplasma gondii it may make you feel differently about cats.

The natural world never ceases to amaze me. While looking up further information on Wolbachia bacteria I found an interesting article on parasites that manipulate sex and reproduction in their hosts that was absolutely fascinating which covered the effects of eliminating the Wolbachia bacteria in parthenogenetic insects. Fascinating.

Had heard tell of toxoplasmosis before and knew it had something to do with cats but hadn’t really looked into it any further until now. Incredible the way Toxoplasma gondii affects rats too…..

Also, along the lines of what you saw with the hoverflies, take a look at the pictures below from Brazil. They show hemipteran bugs that have been parasitized by a Cordyceps fungi. The really long threads are the fruiting bodies of the fungi and like your hoverflies, the fungi has made the insect climb up high and cling on to distribute the spores.

Thanks for the pictures. Makes you think a little differently about fungi doesn't it?

Check these out too:
Perilitus coccinellae - some threads and pics on here a while ago about this wasp
Ampulex compressa

These are parasitic wasps, but here, venom is important in host behaviour modulation.

Very interesting, Ampulex compressa in particular.

What we know about this sort of stuff is really the tip of the iceberg. I'd wager that any organism that lives on, or more specifically in, another organism must change the host to suit itself. These relationships have evolved over tens or hundreds of millions of years, so there must be some crazy things going on.

Thanks again for the time you have spent explaining all of this to me and for introducing me to some fascinating parasites. I will have to do more research on this subject, you have provided me with enough material to keep me busy for months.

Also thank you, once again, to Jason for the initial identification.

Sienna

[Fritillary]

Quite fascinant the world of parasites There are similar histories about fish that get an parasite, so the fish go to the surface where it is caught by a bird and like that the parasite can be jumping from animal to its definitive host.
It is a little like a halloween story, the parasite take the will of the host.

[loripo]

This is a fly I photographed earlier this year that has the Entomophthora fungal infection.