Glassberg is quite correct.

[Neil Jones]

On 10 Jan, in article <3C3DB691.E023150F at home.net>
     mikayak3 at home.net "Mike Soukup" wrote:

> Can't help myself this time.....
> 
> To compare a Hymenopteran - that uses chemical signals, vision in the non-human
> spectra and other methods for finding it's prey and a "human with a net" is
> ludicrous. 

I'm sorry I don't understand. What is ludicrous about this? Both have the effect
of removing individuals from a population. In the mathematical models that I
have seen about the ecological effects of predation, predator not equals
Homo sapiens is not written in to the equations.



   Second, you only state that "they have effects on the
>  populations" -
> well - duh!  What predator doesn't. 

I am puzzled. Then you must accept my point. Human predation can affect
butterfly populations.



>   Then, you start on Snail.  Sorry, wrong
> Phyllum.  Try again.

Why? 

> And, even if the wasp did "make them extinct", it was a wasp that did it -
> not a
> man.  So, you either want man to be part of nature (equating him with the
> wasp)
>  -
> in which case, man causing an extermination is no more evil than any other
> "natural" predator causing the extermination, or, you want man to be "separate
> from nature" - in which case comparing him to a wasp or a snail is not valid. 
>  You
> can't, logically, have it both ways.  Period.
>
No. We were debating whether it was reasonable for us to have laws preventing
_humans_ from predating species that we wish to conserve. It has nothing to
do with man's part of nature.
 
> And, not being organized or knowledgable enough to have the details - but I
> know
> there was a study done "out west" where a localized checkerspot colony was
> "collected" as thouroughly as humany possible (eggs, larve, pupae, adults). 
>  This
> practice had no effect on the successive populations.  So, I would say 
> there is
> MUCH more evidence supporting the lack of exctinction by collecting - than
> there
> is evidence supporting extinction thru collecting.

No, this is not the case. You have not remembered the study correctly.
It is referred to in:-

'Checkerspot Butterflies: A Historical Perspective',
by Ehrlich, White, Singer, McKechnie, and Gilbert (1975), Science 188:221-
228

They collected _adults_only_ and they reported that they could only remove
5-25 % of the females. This just wasn't enough to do damage. This is 
particularly the case when you consider that a female checkerspot can lay 
a large batch of eggs (up to around 288) on the day she hatches. 

There are two further reasons why reducing populations to lower levels
threaten the survival of a population. One is inbreeding which has been
established to cause an increasing likelihood of extincion in populations
of the Glanville Fritillary (An Eurasian Checkerspot).
I don't have a reference handy but it was published in Nature a few years ago.

The second is the Allee effect which means that in small populations
individuals have a tendency to wander off and not breed. This was also
established in butterflies in a study on The Glanville Fritillary.

Both these effects would increase as the population got smaller so reducing
it by human predation would further endanger it.

If you have _evidence_or_a_logical_argument that invalidates the research
then I would be glad to hear it.  You cannot however dismiss a scientific
argument out of hand as "ludicrous" without evidence.



-- 
Neil Jones- Neil at nwjones.demon.co.uk http://www.nwjones.demon.co.uk/
"At some point I had to stand up and be counted. Who speaks for the
butterflies?" Andrew Lees - The quotation on his memorial at Crymlyn Bog
National Nature Reserve


 
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