[NatureNS] kelp flies

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From: c.majka@ns.sympatico.ca
Date: Wed, 21 Feb 2007 08:54:23 -0400
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Hi Steve,

Although my knowledge of insect physiology is minimal I can make a =20
couple of comments:

1) Decomposition produces heat and the environment where these flies =20
live - large heaps of decomposing seaweed - may stay warmer than the =20
local ambient temperature thanks to their internal heat-generating =20
capacity. This may allow these flies to stay relatively active year-=20
round.

2) In my work on sub-cortical beetles I've found a suite of insects =20
that remain active all winter. The environment under bark is rather =20
sheltered and when the sun comes out in the winter, dark bark quickly =20=

absorbs sunlight and the space under the bark warms up. If you peel =20
back the bark of trees in the early stages of decomposition (i.e. =20
when cambium feeders are still active and the bark has not yet begun =20
to physically crack open and break-down) on a sunny day, the beetles =20
that are found there (bark beetles, aleocharine rove beetles, and =20
others) are often quite active. Of course when the sun disappears and =20=

the temperature goes down, they rapidly slow down. ;->

Although I've never investigated the physiology of beetles in this =20
micro-environment, I would think they would have to have really =20
effective anti-freeze mechanisms in order to to make these relatively =20=

fast physiological adjustments on a daily basis.

In general I think that small, dark-coloured entities like many =20
insects can be very adept at absorbing sunlight and thus raising =20
their body temperature above the ambient. Snow-fleas (Collembola) =20
certainly thrive in these circumstances.

All the best!

Chris

On 20-Feb-07, at 11:32 PM, Stephen Shaw wrote:

> Hi Murray,
> That's an intriguing observation.  Roughly what temperature would =20
> it have been
> when you saw this, below zero?  I'm interested generally in flies =20
> and didn't
> realize that any adults of such groups were around at these =20
> temperatures, or at
> all in February.  As a sort of reference point, I recall reading =20
> that the UK
> low-temperature record for an insect "behaving" was -5=B0C for a =20
> bristletail
> (wingless insect) that someone observed sitting on a seaside rock =20
> in Wales,
> whereupon it promptly ran away.  I found that it takes a -7=B0C =
surface
> temperature (aluminium)to immobilize the same species that we also =20
> get here
> (they hibernate over winter here in sea cliff crevices). Flies like =20=

> other
> insects are cold-blooded, and many cell systems like important =20
> enzymes have
> temperature optima and slow down and eventually shut off when the =20
> temperature
> drops, so the animals then can't perform at all, e.g. fly around.
>
> I think that 'kelp flies' is a name usually restricted to the =20
> family Coelopidae,
> with only a few species here in the genus Coelopa.  The Manual of =20
> Nearctic
> Diptera doesn't mention anything about year-round adults or low =20
> temperature
> behaviour, though that's not the main thrust of MND so perhaps this =20=

> doesn't
> mean much.
>
> Maybe all this is well-known locally here -- has anyone else seen =20
> these flies
> flying around recently, for instance while birding around the high =20
> tide line? They tend to fly in small low clouds around piles of =20
> seaweed washed up there,
> in summer.  If anyone has info and has an idea of what the =20
> temperature was at
> the time, it would be interesting to hear about it.  Do birders =20
> ever set out
> armed with digital thermometers, now quite inexpensive?
> Steve, Halifax
> ****************************
>
> Quoting dowitcher <dowitcher@eastlink.ca>:
>> on sunday at clam point i had kelp flys flying around in among all =20=

>> this snow.
>>
>> Murray R Newell
>> Cape Sable Island
>> Nova Scotia

_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._.=20=

_.
Christopher Majka - Nova Scotia Museum of Natural History
1747 Summer Street, Halifax, Nova Scotia, Canada  B3H 3A6
(902) 424-6435   Email <c.majka@ns.sympatico.ca>
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._.=20=

_.


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<HTML><BODY style=3D"word-wrap: break-word; -khtml-nbsp-mode: space; =
-khtml-line-break: after-white-space; ">Hi Steve,<DIV><BR =
class=3D"khtml-block-placeholder"></DIV><DIV>Although my=A0knowledge of =
insect physiology is minimal I can make a couple of =
comments:</DIV><DIV><BR class=3D"khtml-block-placeholder"></DIV><DIV>1) =
Decomposition produces heat and the environment where these flies live - =
large heaps of decomposing seaweed - may stay warmer than the local =
ambient temperature thanks to their internal heat-generating capacity. =
This may allow these flies to stay relatively active =
year-round.</DIV><DIV><BR class=3D"khtml-block-placeholder"></DIV><DIV>2) =
In my work on sub-cortical beetles I've found a suite of insects that =
remain active all winter. The environment under bark is rather sheltered =
and when the sun comes out in the winter, dark bark quickly absorbs =
sunlight and the space under the bark warms up. If you peel back the =
bark of trees in the early stages of decomposition (i.e. when cambium =
feeders are still active and the bark has not yet begun to physically =
crack open and break-down) on a sunny day, the beetles that are found =
there (bark beetles, aleocharine rove beetles, and others) are often =
quite active. Of course when the sun disappears and the temperature goes =
down, they rapidly slow down. ;-&gt;</DIV><DIV><BR =
class=3D"khtml-block-placeholder"></DIV><DIV>Although I've never =
investigated the physiology of beetles in this micro-environment, I =
would think they would have to have really effective anti-freeze =
mechanisms in order to to make these relatively fast physiological =
adjustments on a daily basis.</DIV><DIV><BR =
class=3D"khtml-block-placeholder"></DIV><DIV>In general I think that =
small, dark-coloured entities like many insects can be very adept at =
absorbing sunlight and thus raising their body temperature above the =
ambient. Snow-fleas (Collembola) certainly thrive in these =
circumstances.</DIV><DIV><BR =
class=3D"khtml-block-placeholder"></DIV><DIV>All the best!</DIV><DIV><BR =
class=3D"khtml-block-placeholder"></DIV><DIV>Chris</DIV><DIV><BR><DIV><DIV=
>On 20-Feb-07, at 11:32 PM, Stephen Shaw wrote:</DIV&