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<DIV>Let me introduce myself my name is Peter and I live near Paris in France. I am a beginner in the study of hoverflies and recently subscribed to this forum. </DIV>
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<DIV>I am not confronted with such temperature differences, but I was wondering if there is a threshold when tempérarure is very low for the survival of hoverflies. Do you also have noticed a decline in the number of hoverflies due to different heat waves.</DIV>
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<DIV>Best Wishes</DIV>
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<DIV>Pierre<BR><BR></DIV>
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<DIV><STRONG><FONT face="bookman old style, new york, times, serif"><FONT size=2><FONT color=#0000bf>Pierre MILLE</FONT> </FONT></FONT></STRONG></DIV>
<DIV><STRONG><FONT face="bookman old style, new york, times, serif"><FONT color=#0000bf size=2>3 avenue des buttes blanches</FONT></FONT></STRONG></DIV>
<DIV><STRONG><FONT face="bookman old style, new york, times, serif"><FONT color=#0000bf size=2>95220 Herblay</FONT></FONT></STRONG><FONT face="times new roman, new york, times, serif" color=#0000bf><STRONG>
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<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px"> </BLOCKQUOTE></BLOCKQUOTE></STRONG></FONT><BR><BR>--- En date de : <B>Mar 9.2.10, Frank Van de Meutter <I><Frank.VandeMeutter@Bio.kuleuven.be></I></B> a écrit :<BR>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid"><BR>De: Frank Van de Meutter <Frank.VandeMeutter@Bio.kuleuven.be><BR>Objet: Re: [Syrphidae] freeze tolerance in tree-hole species<BR>À: "Hoverfly discussion list" <syrphidae@lists.nottingham.ac.uk><BR>Date: Mardi 9 Février 2010, 14h27<BR><BR>
<DIV id=yiv618531274>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 type="cite"><PRE>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="http://fr.mc275.mail.yahoo.com/mc/compose?to=Frank.VandeMeutter@Bio.kuleuven.be" target=_blank rel=nofollow ymailto="mailto:Frank.VandeMeutter@Bio.kuleuven.be"><Frank.VandeMeutter@Bio.kuleuven.be></A>
To: <A class=moz-txt-link-rfc2396E href="http://fr.mc275.mail.yahoo.com/mc/compose?to=syrphidae@lists.nottingham.ac.uk" target=_blank rel=nofollow ymailto="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>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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