A strange title to a blog post you may say, but what I learnt about today is one of Nature’s mysteries and fascinating phenomena and it was happening right here in my garden!
I went up to collect my washing in and as I got to my son’s jeans, I noticed something along the bottom hem. I was amazed to find about 10 flies, all hanging off the bottom, with white abdomens. At first, I thought they were empty pupae cases and these flies had shed a skin or similar. On closer examination, I could see that this was not the case. The flies were all dead, but all strung out in a line as if they had sacrificed themselves in some bizarre macabre ritual. Looking a little more closely, I discovers about 10 more flies, spread out around this one pair of jeans; a couple on the pocket and some along the waistline….. not any on the rest of the washing…. just the jeans!
I had no idea what was going on here, so I tweeted a picture… Twitter is a superb way of tapping in on experts from all over the world and it was not long before I heard from Ian Beavis and Ryan Clark with some suggestions… that what I had found were Zombie Flies!!! I had never heard of this, but as the day progressed, more experts got in touch and I did some research, I found out some truly fascinating facts!
My flies seemed to have a band of white fuzz around each segment of their abdomen…
This ‘fuzz’ is, in fact a kind of fungus. … the Entomophthora muscae fungus and you just won’t believe what it does! Entomophthora muscae is a species of pathogenic fungus which causes a fatal disease in flies.
Soon after a fly dies from infection with this pathogenic fungus, large primary spores are produced which emerge from the inter-segmental membranes on the abdomen… what I saw on the abdomen of my flies. When the spores are mature they are forcibly ejected and may fall onto flies resting nearby.
The fungal spores germinate within a few hours and a germ tube begins to penetrate the insect’s cuticle. The mycelium (tiny roots) of the fungus may grow into an area of the brain that controls the behaviour of the fly, forcing it to land on a surface and crawl upwards. The fungus gradually grows through the whole of the body, digesting the guts, and the fly dies in about five to seven days. When it is critically ill, it tends to crawl to a high point, straighten its hind legs and open its wings, a behaviour that ensures that the fungal spores are dispersed as widely as possible. This is what happened in my case. Ian thinks the blue of the jeans attracted the flies, which is why they were only on this item of clothing.
Some three hours later, the fungal fruiting body starts to develop and a new shower of spores is released. so, this fungus actually controls the fly and affects its behaviour to ensure that the spores are spread…. how completely amazing is that?!!
I was also contacted on Twitter by David Hughes in USA. He works in his ‘Hughes Lab’. The lab is part of the Center for Infectious Disease Dynamics and The Huck Institute for Life Science @ Penn State. We are located at the MSC and David is a faculty member of both Entomology (College of Ag Sciences) & Biology (Eberly College of Science). Much of the research driving the lab is at the intersection of disease & behavior: how and why parasites manipulate host behavior and what is the role of behavior in reducing disease transmission. David is an expert of this and I took a look at his website… http://www.hugheslab.com and it was truly fascinating stuff.
David produced the film in David Attenborough’s Life On Earth about Zombie Ants and this video explains the principle behind these amazing fungi really well….
Thank you so much to all who got in contact with me today. Nature is truly amazing and it just goes to show that if you keep your eyes open, you just never know what you may find happening in your own garden! Nature is truly amazing isn’t it?!