Subject: Migrants in Sicily June 1996

From: "J.B.Murray (John Murray)" <[email-masked]>
Date: Mon, 1 Jul 1996 15:49:04 +0000

On a recent trip to Mt Etna, Sicily, I made a few measurements of butterfly
flight speeds etc. whilst waiting for GPS to collect data.  Apart from the 2
species below, I also saw Red Admiral (V.atalanta) and Large Tortoiseshell for
the 1st time in Sicily, plus Brimstone (G.rhamni), Wall (L.megera), Bath White,
Swallowtail, various kinds of Grayling, Small Tortoiseshell (A.urticae), Brown
Argus (A.agestis), Gatekeeper (P.tithonus), Purple-shot Copper, Spotted
Fritillary, Holly Blue (C.argiolus) and many others I couldn't put a name to,
including a butterfly resembling an Apollo.

I was surprised to find Painted Ladies (C.cardui) at about the same frequency as
in England when I left; i.e. about one every 2 minutes, flying persistently NE.
In contrast to the UK, the commonest butterfly was usually the Large White
(Pieris brassicae), or occasionally the Small White (P.rapae).

Measurements summarised as follows:

Painted Lady:  (C.cardui):
Date      Time    Temp(C)  Alt.  Frequency     Speed ms-1  Direction    No.

June 9   15h10m     27     733   every 2 min  3.8 +/- 0.4   45           5
June 10  11h27m     25     733   every 2 min                52           5
June 11  10h51m     28     973   every 3 min  5.1 +/- 0.9   50 +/-39     4
June 13  12h30m     26    1122                              23           1
June 16  10h40m      7    2925                              28           3
June 16  11h40m      8    2430   every 1 min  5.9 +/- 0.8   79 +/-19     3

MEAN:                                         4.9           49 +/-23

Large White:  (P.brassicae):
DATE      Time    Temp(C)  Alt.  N per km     Speed ms-1   Direction    No.

June 9   09h00m           1200     5000                    90 approx  c100
June 9   15h10m     27     733     1690      3.3 +/- 1.1   10 +/-101    29
June 11  10h30m     28     973    17300                                524
June 11  16h00m     32     225      100                                  1

MEAN                               6023                       50

Alt. is altitude in metres, speed is in metres per sec., direction is the
direction of flight in degrees east of north; N per km is the extrapolated
number per square kilometre based on several counts of butterflies within a
defined area, No. is the number of individuals on which the measurements were
based.

The 2 species behaved very differently.  The Painted Ladies looked as is they
were migrating, flying steadily without stopping and usually in a straight line
less than a metre above the ground, and at any given location the direction of
flight varied little.  The Large Whites were not apparently migrating,
frequently stopping at flowers, and flying in apparently random directions at
some locations.  However, after averaging large numbers it is interesting to
note that both species are travelling on average in almost identical directions.
 If continued, the flight direction would bring them right up the centre of the
toe of Italy.

The mean speed of Painted Ladies is 18 km per hour, which assuming they fly 8
hours per day would bring them to the UK or Denmark in about a fortnight.  The
mean speed of Large Whites in flight was only 12 km per hour, but they seemed to
spend at least half their time stopping and feeding, so their mean advance might
be only 6 km per hour.  Assuming the same flight period, this would bring them
to the UK or Denmark in nearly 40 days, so if there is a sudden influx of Large
Whites around July 20th, you'll know where they came from!  Last year, Large
Whites in Herts., UK peaked on July 30th.

Finally, does anyone have any thoughts on the direction of flight bringing both
these species right to the centre of the best overland route?  If they flew due
north, as they were doing in the UK before I left in early June, this would
bring them to over 200 km of the Tyrrhenian Sea, which neither species could
cross in one day's flight.  Their 50 deg bearing brings them close to the
Straits of Messina and a sea crossing time of 1 hour (Painted Lady) or 3 hours
(Large White) only.

Is this coincidence, or do these butterflies really carry some kind of primitive
migratory map in what passes for a brain?

John Murray
[email-masked]
Marshalls Heath,
Herts., UK

---

From: Paul Sammut <[email-masked]>
Date: Mon, 1 Jul 1996 18:02:08 +0200

The 'apollo -like' butterfly that you have seen on Mount Etna, could it have
 been an
Aporia crataegi?. Parnassius apollo siciliae, if it still exists is found
 further north
on the Madonie mountains ranging from Messina towards Palermo.
Paul Sammut
[email-masked]
MALTA

---

From: [email-masked] ("Colin Cracknell")
Date: Sat, 6 Jul 1996 14:25:32 GMT

> Their 50 deg bearing brings them close to the
> Straits of Messina and a sea crossing time of 1 hour (Painted Lady) 
> or 3 hours (Large White) only.
<snip>
> Herts., UK

Shouldn't that be 2 hours for Large White? They're not going to stop and 
rest in the middle!
------------------------------------------------------------------
[email-masked] | "Ask not for whom the book burns, 
                           | it burns for thee." ([email-masked])
All opinions are my own, but Darter Systems agrees with me.
------------------------------------------------------------------