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fruitflies - or Megaselia?

Alan C. Christensen, Ph.D. acc at BIOCOMP.UNL.EDU
Wed Aug 26 08:16:41 EST 1998

LPeacockBr at AOL.COM <LPeacockBr at AOL.COM> wrote:
:Please advise me on how to rid my home of fruitflies!!! I have a terrible
:problem and it is out of control. I have used Lysol to kill them, but each
:morning I have many more. I am desperate for any help.

There are questions like this posted to dros.bio.net at regular intervals.
However, some of the time the infestations may not be fruit flies.  We have
recently had a problem with Megaselia scelaris in our building.  Megaselia
are a genus of diptera in the phorid family, but they look a lot like
Drosophila, especially when they are flying around trying to share your
coffee or lunch.  When they are walking on a surface they are noticeably
different: they tend to move quickly in short bursts, unlike Drosophila,
hence the common name for them of scuttle flies.  They are also slightly
larger, especially the females.  Under the microscope they look somewhat
like Drosophila, except the hind legs are bigger and more muscular - kind
of grasshopper-like - and they have nasty-looking (IMHO) black eyes.

Other occupants of the building often complain about them to the Drosophila
labs, but they are a pest for us too.  If they invade fly cultures they can
cause a lot of trouble.  The larvae are bigger and more aggressive feeders,
and will take over a vial.  The life cycle is slower than Drosophila
melanogaster, by about 7-10 days, and I think they go through 3 larval
molts.  The last instar larvae are bigger, and can fairly easily get
through cotton balls.  They can also poke through a layer of parafilm, and
apparently can even go through plastic trash bags.

Megaselia are scavengers and will breed in any moist organic material
including insect carcasses (roaches and crickets that have died under a
refrigerator for instance), sludge in the bottom of trash cans that don't
get washed out regularly, old plates that haven't been tossed, autoclaved
waste that isn't tightly double-bagged, liquid in the bottoms of aluminum
cans and plastic bottles that are sitting in a recycling bin, etc. etc.
They are also the bane of the mausoleum industry, because the females lay
eggs at the cracks of "sealed" coffins, and the larvae are very good at
getting in and feeding, hence their other common name, coffin flies.

As with a Drosophila infestation, the thing to do is get rid of the food
sources, but bear in mind that it isn't just fruit.  There is a report of a
disconnected sewer line under a house which was hosting Megaselia by the
thousands in the sludge on the inside of the pipe.

If anyone has experience with these, and has a good way of getting rid of
them without harming Drosophila, I would appreciate knowing about it.
Megaselia are endemic throughout the world (there are hundreds of species
described), and are a Drosophila lab pest, and also a pest for people
around Drosophila labs, who then blame the lab.  So far all we've come up
with is improved custodial service, and hanging up sticky fly paper.

* Alan C. Christensen, Ph.D.          "...there are those rare  *
* School of Biological Sciences        characters who study the *
* University of Nebraska               unknown product of an    *
* Lincoln, NE 68588-0118               unknown gene.  These we  *
* Phone 402-472-0681                   call lunatics."          *
* FAX 402-472-2083                            -Sidney Brenner   *

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