Ruud Kleinpaste: Queries about cluster flies in houses

A common problem in our homes, especially in the cooler areas of Aotearoa: gazillions of flies settling into your spare room, on the ceiling of a quiet place, or in the roof cavity.  

The flies arrive at your place in autumn and find a good spot to hibernate – just like they do in their countries of origin: Sweden, Finland, Netherlands, Germany, the UK, the USA, and Canada.   

Pollenia pediculata is the cluster fly species we discovered on the North Shore for the first time in 1984. It may have arrived in some containerised luggage or cargo (we were not sure when we found it), it’s now well-spread, often in the cooler spots of our country.  

It is quite a gorgeous fly species, with golden hairs on its back – easy to spot as it often sits quietly.  

Flies have just one pair of wings whereas other insect orders usually have two pairs of wings in the adult stage. The second pair of wings is turned into small “halteres”: modified hind wings that provides stability when in flight.  

Flies are real acrobats: they can fly up-side-down onto the ceiling  

Our cluster fly lives a peculiar life as a parasite of earthworms.   

The female fly lays eggs in dense grass habitats (paddocks and lawns) and often near or in earthworm tunnels.  

The larvae (aka "maggots") hatch, find themselves some way of getting into the soil (gaps around plants or through established earthworm tunnels) and gain entry into the body of an earthworm.  

Inside the worm it feeds on the internal body fluids and organs.   

Gross? Yep! But these flies do minimal damage to earthworm population densities. 

Most animals on the planet have "parasites" that can cause damage (humans have parasites too). In spring and summer, I often see them pollinating flowers (the name “Pollenia” is a nice indicator!). 

When temperatures get cooler in autumn, the cluster flies usually look for a suitable hibernation place: holes in the ground, under bark of trees, under mulch layers, etc. But if there’s a nice warm human house nearby, they will try to gain entry – by the thousands!  

They crawl through small holes (ill-fitting window frames, etc) and mark their entry by leaving a residue of pheromone scent – this means that other Pollenia flies simply follow the trail and join the others. 

The pheromone is rather sticky and smells somewhat of Buckwheat honey (hence the name buckwheat fly in the USA).  

Cluster flies are not of medicinal importance (like some blowflies) but are hard to remove due to their messy pheromones. Best “prevention” is to ensure there are no entrance holes around the home.  

A very residual aerosol can (available from SafeWorx – safety company) sprayed at the flies’ entry and exit holes, will stop them from getting inside.   

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Episode Transcript

Speaker 1 (00:07):
You're listening to the Saturday Morning with Jack Tame podcast
from News Talk ZEDB. Rude climb Past is in the
garden for us this morning talking clusterflies, which is the
sort of thing that most of us would be disgusted by,
but of course Rude is a little bit delighted by
as well.

Speaker 2 (00:22):
Good mornings there, good finding Jack. You do realize that
the clusterflies were in discovered by talkback callers on news
Talks EDB in nineteen eighty four.

Speaker 1 (00:34):
No, are you serious?

Speaker 2 (00:35):
There you go? Yeah, absolutely. I was working for the
Ministry of Anger and Fisheads or meth whatever they call themselves,
and we got these complaints of these funny little flies
that were coming in the north shore. That was in
nineteen eighty four, and we went out and there to
look and found, Oh gosh, it's the new species. This
new to New Zealand. That's the cluster fly from Europe basically,

(00:56):
and it came in probably on some cargo and ships
and things like that. Oh goodness, Yeah, it was I
won't forget that. It was really cool fun because I
was just working meth for the first year or so
and there we went. That was great fun. But those
flies are actually quite lovely if you see them. They're
very common in the South Island, by the way, and
probably also common in the cooler places of the North Island.

(01:19):
So I thought, I'll just there's a lot of that
stuff on the on the on the website, so you
can read it all. I know that all the time
in the world. Gorgeous fly, golden hairs on its on
its back. It's beautiful actually, size of a blowfly, that
sort of thing. Yeah, and a parasite of earthworms.

Speaker 1 (01:38):
Oh really, it lays.

Speaker 2 (01:40):
Eggs in earthworm burrows and then the maggots basically killed
the earthworms. It's not any any major thing for the
earthworm population. It doesn't seem to, you know, hassle them
that much. But then comes this time of the year
and all the adult cluster flies are getting together. They
work together a little bit like that Vatican stuff, you know,
they work together. They stick their fingers up and said,

(02:01):
this is where we go, and they put an pheromone
trip into this hole the whole where they go into
somebody's house or under the house or in the ceiling,
and that's where they will be for the winter. And yeah,
it's cool stuff. But the problem is they've got this
sticky fair amount which is quite rubbishy stent and nasty

(02:23):
and all that and smells like buckwheat honey, and it's
really hard to control those things. And I know you
probably haven't had them in Auckland where you are, but
if you try to get rid of them, they're all
the stick and stuff and grime will stay everywhere. So
here is the best way to go about it. It's
an oily material of course that they leave anywhere on

(02:46):
the services. But if you get a residual aerosol cane
from Safe Works. We've talked about this before. Safe Works
is a company that has aerosolt cans that we designed
for aircraft sprays and things like that, long lasting, you
can actually get rid of them without causing too much
extra mess for yourself. That's really what it's about.

Speaker 1 (03:06):
Okay, Yes, you just get the aerosol can, very good
and it's Safe Works with an X, isn't it like
Safe Work.

Speaker 2 (03:12):
At the end? You got it? Yeah, yeah, yeah, that's
the US okay now, But honestly it's the way to
go about it, and you'll find you will be able
to stop them from going in and out because the
pheromone will be basically toxic by then they won't get in.
Oh very good.

Speaker 1 (03:25):
Hey, thanks RhoD, appreciate that.

Speaker 2 (03:27):
So boy to welcome through climb pass in the garden
with the clusterfliers for us this morning.

Speaker 1 (03:33):
For more from Saturday Morning with Jack Tame, listen live
to News Talks' b from nine Am, saturday or follow
the podcast On. iHeartRadio