Hi, I noticed a phenomena occurring with what appear to be house flies, the...

Asked August 22, 2014, 11:29 AM EDT

Hi, I noticed a phenomena occurring with what appear to be house flies, the blue ones and green ones. I have seen many swarming around my diamond ornamental grass and my Norfolk pine and tomato plants. They are all in pots and next to each other. these flies have landed on the blades of the grass and the tips of my pine and under my tomato plant leaves. they appeared to be resting on them but closer look at them they are dead and stuck to the plan leaves. Some are covered in a brownish or tan crust. the abdomin rings on some appear to have seeped a tan fluid and crusted over. They appear to me that a predator of the flies capture them on the plants and seal them in this brownish crust for later feasting. Just not sure what to think of this. I noticed just the other day near by, in my lawn a tall blade of grass has about 5 blue green flies lining the blade. I thought when I bumped the blade they would fly off, but just like on my plants the flies were dead and dry and stuck to the blade. Do they go to these areas to die off and then deteriorate? Or are they being captured by some predator like a spider? I have never seen this before and am very curious. What can you tell me about this phenomena? I haven't got a picture.

Hennepin County Minnesota

2 Responses

I asked one of the entomologists from the U about your question and here is the answer. Sorry we can't be more specific.

Sounds like she is describing blow flies. They are attracted to dead animals and rotting garbage and are common. They can be found on plants. They feed on pollen and sometimes land on leaves if they resting.

I don't know why they are dead in this case. Fungus can kill seedcorn maggot flies in the early summer, http://blog.lib.umn.edu/efans/ygnews/2014/06/dont-be-fooled-by-fungus-kille.html. The way the blow flies are described on the plants sounds similar although I have not seen this happen to blow flies. It is hard to say what is going on without a picture.

Thankyou for your response. I guess the flies could be seed corn flies as you have described. I read the article and it is right on about what I have seen with the flies. I believe it is a fungus. As the article describes that as they die the segments separate with fungus and I have seen that as well. I am convinced it is a fungus thanklyou for checking it out for me.