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In Belgium Melanyna quadrimaculata is on the wing since the 2th of
march at ambient temperatures of about 3°C.<br>
Overwintering species (E. tenax) have been sighted already somewhat
earlier.<br>
<br>
Relating to the earlier subject on overwintering treehole species and
freezing. So far no dead larvae found. Searching was rather succesful
with both Myolepta and Mallota larvae found recently in Fagus!<br>
<br>
cheers<br>
Frank<br>
<br>
<br>
Pierre MILLE schreef:
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<div>Hello to all</div>
<div> </div>
<div>In my home (Ile-de-France in Herblay in the Val d'Oise)
temperature is 10 ° C and the sun hot ! Have you seen your first
hoverflies?This would symptahique answer me because I sent two messages
of welcome and others asking questions but I've never had any answers.<br>
<br>
Best wishes</div>
<div> </div>
<div>Pierre</div>
<div>
<div><strong> Pierre MILLE </strong></div>
<div><strong> 3 avenue des buttes blanches </strong></div>
<div><strong> 95220 Herblay </strong> <strong>
</strong>
<p></p>
<blockquote>
<blockquote> <strong> </strong> </blockquote>
</blockquote>
<br>
<br>
--- En date de : <b>Ven 12.2.10, Bartsch, Hans D <i><a class="moz-txt-link-rfc2396E" href="mailto:hans.bartsch@telia.com"><hans.bartsch@telia.com></a></i></b>
a écrit :<br>
<blockquote><br>
De: Bartsch, Hans D <a class="moz-txt-link-rfc2396E" href="mailto:hans.bartsch@telia.com"><hans.bartsch@telia.com></a><br>
Objet: Re: [Syrphidae] freeze tolerance in tree-hole species<br>
À: "Hoverfly discussion list" <a class="moz-txt-link-rfc2396E" href="mailto:syrphidae@lists.nottingham.ac.uk"><syrphidae@lists.nottingham.ac.uk></a><br>
Date: Vendredi 12 février 2010, 14h26<br>
<br>
<div>
<div> Dear all, </div>
<div> 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 don´t get worried! The
only thing to remember is that there should be drier material for the
larvae to pupate in when that time cames. </div>
<div> Best wishes </div>
<div> Hans </div>
<blockquote>
<div>----- Original Message ----- </div>
<div><b>From:</b> <a moz-do-not-send="true"
title="Frank.VandeMeutter@Bio.kuleuven.be"
href="http://fr.mc275.mail.yahoo.com/mc/compose?to=Frank.VandeMeutter@Bio.kuleuven.be">Frank
Van de Meutter</a> </div>
<div><b>To:</b> <a moz-do-not-send="true"
title="syrphidae@lists.nottingham.ac.uk"
href="http://fr.mc275.mail.yahoo.com/mc/compose?to=syrphidae@lists.nottingham.ac.uk">Hoverfly
discussion list</a> </div>
<div><b>Sent:</b> Tuesday, February 09, 2010 2:27 PM</div>
<div><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 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 moz-do-not-send="true"
href="http://fr.mc275.mail.yahoo.com/mc/compose?to=Frank.VandeMeutter@Bio.kuleuven.be"><Frank.VandeMeutter@Bio.kuleuven.be></a>
To: <a moz-do-not-send="true"
href="http://fr.mc275.mail.yahoo.com/mc/compose?to=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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