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<DIV><FONT size=2 face=Arial>Dear all, </FONT></DIV>
<DIV><FONT size=2 face=Arial>I can only confirm from the Stockholm area what
most allready have written. I was breeding Myatropa florea larvae in a small
bucket (with wooden chips in water) the other year and everything froze to one
block of ice. Nevertheless the larvae pupated and hatched next spring without
problems. So do not touch and donīt get worried! The only thing to remember
is that there should be drier material for the larvae to pupate in when that
time cames. </FONT></DIV>
<DIV><FONT size=2 face=Arial>Best wishes </FONT></DIV>
<DIV><FONT size=2 face=Arial>Hans</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=Frank.VandeMeutter@Bio.kuleuven.be
href="mailto:Frank.VandeMeutter@Bio.kuleuven.be">Frank Van de Meutter</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=syrphidae@lists.nottingham.ac.uk
href="mailto:syrphidae@lists.nottingham.ac.uk">Hoverfly discussion list</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, February 09, 2010 2:27
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Syrphidae] freeze tolerance
in tree-hole species</DIV>
<DIV><BR></DIV>Thanks to all for the swift responses (including several
private ones).<BR><BR>I am well aware that many species may easily cope with
frost just by the simple observation that they do occur in colder climates
than is here the case. No doubt frost-tolerance will be species- and possibly
population-specific. Therefore I still deem it possible that (high) mortality
may occur in some Belgian species, especially in less optimal habitats (small
holes that easily freeze, holes that are too open, ...). Ore maybe some
southern species/populations that had shifted over the past 15 warm winters to
Belgium will now be affected? Also note that species distributions in other
groups may be directly linked to survival of larvae in relation to
temperature, why not in treehole syrphids? (we do have nothern and southern
treehole syrphid species in Europe, don't we?<BR>As such frost may be
responsible for -why not- strong population fluctuations in time or range
shifts. <BR>Anyways, I already observed a Myathropa larva caught in ice -
within a couple of weeks I will see whether such animals may survive (I
now rather have the impression I could break it in two if I broke the ice :)).
<BR><BR>cheers,<BR><BR>Frank<BR><BR><BR><BR><BR>Wouter van Steenis schreef:
<BLOCKQUOTE cite=mid:4B3E65CF7FFC4B549BC72B24746AB63D@PCvanSteenis
type="cite"><PRE wrap="">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
2004.
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!
Wouter
----- Original Message -----
From: "Frank Van de Meutter" <A class=moz-txt-link-rfc2396E href="mailto:Frank.VandeMeutter@Bio.kuleuven.be"><Frank.VandeMeutter@Bio.kuleuven.be></A>
To: <A class=moz-txt-link-rfc2396E href="mailto:syrphidae@lists.nottingham.ac.uk"><syrphidae@lists.nottingham.ac.uk></A>
Sent: Tuesday, February 09, 2010 10:55 AM
Subject: [Syrphidae] freeze tolerance in tree-hole species
</PRE>
<BLOCKQUOTE type="cite"><PRE wrap="">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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