Subject: Re: Collecting vs. populations

From: Gaden Robinson <[email-masked]>
Date: Thu, 16 Feb 1995 13:35:30 GMT

It has long been common belief, now formalised in print in the
butterfly volume of Moths and Butterflies of Great Britain and Ireland,
that A.B. Farn single-handedly wiped out the colony of Araschnia levana
that had been established artificially in (I think) the New Forest and
which had survived for several years. This was not a British species and
Farn objected to this exotic introduction. Now whether the colony died out
because of Farn's depredations or whether it just hit a bad patch of
parasitoids, weather or whatever is moot. I guess there are similar
"extinctions" where collecting as part of adult mortality played a part.
But how big a part?

C.B. Williams looked at the effect of light-traps run continuously over
long periods on moth populations, and I think the question is addressed in
the second part of his paper in 1940 in Trans. R. ent. Soc. Lond. 90: 227-
306.

I am trying to remember the source of a phrase that I sometimes quote
apropos this question, to wit "self-renewing biological resource", but
senility precludes recall. The context was the development of the argument
that natural populations of butterflies or moths are like fish - there is,
by definition, a harvestable component to the population but if that
is exceeded then the whole thing goes to pot. That's the theory and
commonsense suggests it is sound. As to practice and proof - good luck!

As for the ethical component, you have obviously seen the dangers!

I shall be interested to see how your search develops.
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Gaden S. Robinson, Biodiversity Division, Department of Entomology,
The Natural History Museum, Cromwell Road, LONDON SW7 5BD, UK.
Tel.: +44-(0)171-938-9494. Fax: +44-(0)171-938-8937.
INTERNET: [email-masked] [or] [email-masked]
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From: [email-masked] (Neil Jones)
Date: Thu, 16 Feb 1995 21:09:06 +0000

> "extinctions" where collecting as part of adult mortality played a part.

It was actually the Forest of Dean. It is interesting to note that there
has been a similar attempt at establishment recently in Oxfordshire, but
levana only survived for a few generations.

There is also the question of the New Forest Burnet which was apparently
collected to extinction at its last New Forest site by collectors who staked
out the site collecting everything. I do not have a specific reference for this
but E. B Ford in his Book Moths in the Collins New Naturalist Series blames
the "inexcusable avarice of collectors."

As for checkerspots I have been involved in a lot of work with Eurodryas
aurinia here in the UK. Some of the outlying colonies are tiny with two or three
larval webs only being present. This is on sites where it is often possible
to examine every possible foodplant. It would certainly be possible to
collect out these colonies with very little effort.

I also seem to recall a reference somewhere to it being possible to collect
80% of the adults of Mellitea athalia from a colony in one day.

Habitat destruction is of course the major problem but in certain circumstances
collecting must have a part to play where the population is very small.

-- 
Neil Jones