Yet another fly...

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Yet another fly...

Post by jnh »

Here's yet another head shot of a fly. The stack is not as I deep as I wanted, but decent enough.

Now, there was something a bit strange about this fellow, though. I caught this guy with a fly catcher (my daughter is freaking out about flies and needs them dispatched poste haste...), which left the head intact, but did some damage to the abdomen - out of which fell a small ball of what looked like tiny squirming maggots (about 1 - 2 mm in size, maybe a dozen or two of them). Now this intrigued and freaked me out a bit in equal parts, but I was wondering - flies usually lay eggs, don't they? Do some of them carry their young around or was this some sort of parasite?

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Re: Yet another fly...

Post by BugEZ »

flies usually lay eggs, don't they? Do some of them carry their young around or was this some sort of parasite?
Egg laying the norm. Parasite probable . Live birth unlikely, but who knows? There are millions of species of flies...

I am filming the development of long legged fly (Dolichopodidae) eggs (they have finally hatched to larvae!) so I have some amateur dipterist experience.


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Re: Yet another fly...

Post by rjlittlefield »

Consider the discussion at .

Copied here for long-term reference:
What are the little wiggly things that come out when a housefly is killed?
Anthony Mark, studied at University of Queensland
Answered August 16, 2017

One of two possibilities.. one far more likely than the other.

The first would be some sort of parasite that has infected the fly. Of course when any parasite is feeding from its host, it will immediately abandon that host when it is deceased.

However, this is unlikely. House flies and other species can be infected by and transmit parasitic worms, but these are so small as to be all but microscopic so you wouldn't notice them, and would find them difficult to see without a microscope even if you were looking for them. I'm unaware of any parasite a common fly species carries that would be large enough for you to notice evacuating its host.

What you are 99.99% likely seeing are larvae abandoning their dead mother. While almost all fly species lay eggs that then hatch into larvae some time after, some lay live larvae (commonly known as “maggots”). Species with this characteristic are described as ovoviviparous, and is unique to only a few. The housefly is not one of these. However, that doesn't mean that what you saw weren't larvae. Many species of fly that can be found in your home are not houseflies and can be easily mistaken for them as they are very similar in size and appearance.

Without knowing exactly where in the world you are, I'd be almost certain that the fly or flies you've observed this with after you killed them were flesh flies. Flesh flies are commonly found inside homes and are difficult to distinguish from a housefly if you aren't an entomologist or know what you're looking for. Obviously if you have an image that would help with identification. And, yes, flesh flies are ovoviviparous.

The abridged version of the answer is that what you've seen are maggots evacuating their dead mother, but with absolute certainly not from a housefly; with almost near certainly a flesh fly.

As disgusting as it all is, I hope that helps!

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Re: Yet another fly...

Post by jnh »

Thanks - very informative (while slightly disconcerting)

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Re: Yet another fly...

Post by NikonUser »

Besides Flesh Flies there are 4 or 5 closely associated families in the superfamily grouping Hippoboscoidae) that practice viviparity. The adults are bloodfeeders and the larvae develop within the mother.
(from: Erica McAlister 2018 "The Secret Life of Flies).
Book includes 2 of my images!
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

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