Neil Jones Neil at
Fri Jun 20 15:05:51 EDT 1997

Much has been said on the topic of releases recently. I believe that it
is wrong to encourage the public at large to believe that carrying out
releases of butterflies in areas in which they do not occur.
The proposed _mass_release_ of the monarchs is just one example. Not
all of what I have to say applies directly to this species but that release
will serve to educate the public into believing a notion which is simply wrong.
I will try to cover as completely as possible all the ideas which
surround the releasing/introducing mentality. None of this is intended to
be a personal attack on anyone. It is not my desire to start a flame war.

Reinforcement of populations.
The releasing of extra butterflies to increase a population does not work.
The population size is determined by the size and the quality of the habitat.
The population size can only be changed, except in very exceptional
circumstances, by improvements to these parameters.
It is even possible for this kind of release to decrease the population, by
creating a larger population of parasites which then attack the population 
after it has reverted to its normal level, or by exhausting the supply of 


It has been argued that natural selection will eliminate any "bad" genes
which are introduced into a population by the introduction of individuals
from an "alien" population. Unfortunately this matter is not that simple.
There are often genes in a population which may have no effect on the 
individuals which carry them for most of the time but which are of benefit
under adverse conditions. A gene for obesity in humans may be of little
use under time of plenty (even harmful in modern society) but the individuals
who carry it have more chance of suriving during a famine.
Flooding a population with individuals who do not carry "sometimes useful"
genes can cause problems in future generations. These individuals may also
contain "sometimes deadly" genes which could spread for sometime before
natural selection takes its toll.

The two genomes may react most extraordinarily when mixed.
There are elements within the genomes of insects which can become mobile
detaching themselves from their normal place on the chromosome and
re-attaching themselves at random. These "jumping genes" can send the mutation 
rate through the roof causing a large number of deformed or infertile 
individuals to be born. This has already been demonstrated experimentally
with fruit flies.

Illicit introductions

The notion that releasing butterflies is good for conservation tends to
promote the all too common practice of carrying out illicit introductions
of rare species into new areas. This can do more harm than good.

Just a few examples.

A few years ago conservationists trying to save one of the UK's finest
butterfly sites were dismayed to find a developer arguing that 
the population of the magnificent Purple Emperor butterfly (Apatura iris)
should not be conserved because the population only existed as a result
of a local man who had repeatedly introduced significant numbers of captive
reared butterflies into the woods for a number of years.

As a result of illicit introductions in certain parts of the UK it has
become more difficult to ascertain the true conservation status of our
rarest native European butterfly. The Marsh Fritillary (Eurodryas =
Euphydryas aurinia). The species is easily reared in captivity and
misguided individuals persist in releasing them secretly.
Out of over 50 documented examples of this NONE of the resultant colonies
succeded in the long term. The same is true for the majority of the UK's
species that were included in the study.

This practice can divert conservation effort and mask a decline in the species
making it difficult for conservationists to argue the species rarity.


Some populations of an insect may be genetically immune to the effects of a
disease which they carry. Microorganisms can be passed from one generation
to the next. Introducing "alien" organisms could be catastrophic.

I am not argueing against people getting a few common caterpillars
an keeping them in jam jars not that these things will always happen in every
case.  I am argueing against the notion that carrying out releases or
introductions without proper scientific study is potentially dangerous.
Like all environmental matters we should endevour to follow the precautionary

Neil Jones- Neil at "The beauty and genius of a work of art
may be reconceived, though its first material expression be destroyed; a
vanished harmony may yet again inspire the composer; but when the last
individual of a race of living things breathes no more another heaven and
another earth must pass before such a one can be again." William Beebe

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