[Syrphidae] freeze tolerance in tree-hole species

Wouter van Steenis w.v.steenis at casema.nl
Tue Feb 9 13:05:17 GMT 2010

Dear Frank and others,

Don't worry about them larvae and a little frost. In Nebraska (USA) I 
received 6 Mallota bautias larvae from Patrick Monk. He collected them on 
October 4 2003. I kept them in a small plastic container with less than half 
a liter of the substrate collected together with the larvae.
I had the container in a small shed next to our house with temperatures 
equal to outside temperature.
Then winter came. It froze 20 degrees Celsius at daytime for some weeks. I 
don't know the minimum temperature, it must have been quite a bit colder. 
Both the larvae and the substrate were completely frozen. Shaking the 
container sounded like rattling a box with small wood pellets or something.
In spring the larvae came on temperature and went on living as if nothing 
happened. They pupated April 11 and 12 2004. The adults emerged April 27-29 
I know there is quite some literature on how insects manage to freeze and 
stay alive. It has something to do with changing all water content for carbo 
hydroxides so no harm will be done to the cells while freezing.
Off course these frozen insects won't have any cell activity, so they 
probably do not need any oxygen either.

Good luck with your winter search party!


----- Original Message ----- 
From: "Frank Van de Meutter" <Frank.VandeMeutter at Bio.kuleuven.be>
To: <syrphidae at lists.nottingham.ac.uk>
Sent: Tuesday, February 09, 2010 10:55 AM
Subject: [Syrphidae] freeze tolerance in tree-hole species

> Hi all,
> I planned this winter to start a search for some rare water filled 
> treehole/treecavities inhabiting syrphids in Belgium. Winter is however 
> particularly harsh here (and over much of Europe), and all these small 
> water bodies that I visited are frozen for more than six weeks now. It 
> appears to me that the whole of the water content in the tree rotholes and 
> cavities is now frozen. This makes me question whether syrphid larvae will 
> be able to survive these conditions? Even if not all is frozen, they 
> should experience oxygen shortage? Comparably, in ponds and pools, it is 
> known that severe frost may also wipe out a considerable fraction of the 
> aquatic community (though I know nothing on syrphids living there). When 
> the water starts to melt I will see whether many dead larvae can be found. 
> Right now, I would like to ask whether anyone has some previous 
> experience/knowledge on this?
> beste wishes,
> Frank
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