FW: cabbage butterflies

[Guy Van de Poel]

-----Original Message-----
From:	 
Sent:	Tuesday, August 26, 1997 10:30 PM
To:	dglaeske at epping.ndak.net
Subject:	RE: cabbage butterflies

Last year, towards the end of October, I caught several larvae
of Papilio machaon in Haacht - Belgium. This is very late in the
season for this species. I brought them home, and raised them
outdoors on the plant I found them on : Daucus carota, or carrots 
in plain English. In the first weeks of November, the nice weather
we had in October gave way to much colder weather, and frost
at night.

Despite the low temperatures, most of the larvae, already in the
later instars, pupated normally, but I still had two larvae in the
second instar. Unfortunately, I had to move to Germany right
then, so I could only observe them over the weekend when I
was at home in Belgium. After a few weeks I discovered two 
pupae, much smaller than the others. They were approx. 2,2 cm
long, as compared to the 2,7 cm of a normal pupa. Whereas a
normal pupa's with (at the wings cases) is 8 - 9 mm, the smaller
ones measured only 6 mm.

This year, in April, after a very short winter (a couple of weeks in
the fridge), one of them produced a miniature female P. machaon.
>From where the forewing is attached to the thorax to the wingtip
it measures 3,1 cm. The base-to-tip from a normal female is about
4,4 cm. Unfortunately, the other died in the pupa.

Two explanations seem appropriate : 
- Due to the bad weather, they couldn't find sufficient food (it was
frozen), and each instar completed earlier (and smaller) than
normal.
- They (see K. Philip's message on the subject) pupated earlier
after the fourth instar.

I recall reading something on this subject, where a hormone that
is produced after a certain lapse of time in the larva's life will
_force_ the larva to pupate, but most of my books are still in
Belgium, so I would appreciate if anyone could shed some 
light on this matter (I may recall it totally wrong).

To return to the cabbage whites : this unusually cold and wet 
July we had in Belgium produced some aberrant specimens of
Pieris napi. During the only weekend I had the time to go
to Belgium to do some hunting, I noticed several darker coloured
females (2 caught, 3 - 5 more seen). They have the typical 
pattern of the spring generation, one of them even darker.
I know Pierids in the tropics produce darker coloured forms
during the rain season, does this mean the climate in Belgium
is changing toward a tropical one ? :-)
In comparison to specimens of the first generation however, they
are rather large-sized, even compared to the second generation
females in my collection.

Greetings,

Guy Van de Poel

Guy_VdP at msn.com