On 4 May 2004 08:16:58 GMT, Nick Maclaren wrote:

In article m,
Tim Challenger "timothy(dot)challenger(at)apk(dot)at" writes:
|
| They do protect some aphids. I've seen (presumably) young pale aphids being
| nurtured in a few nests I've dug up in winter. They overwinter them in the
| nest and bring them out onto the young shoots in spring. The ants often
| drive off potential predators, so allowing the aphids to increase. So it's
| not exactly farming, more like shepherding.

Are you sure that you weren't confusing dairy and beef cattle?
:-)

Both may well occur, but your "often" is definitely wrong. At most,
"sometimes".
Maybe I got lucky. They were in at least every third or fourth nest I dug
into (normally accidentally) during the winter. A small sample admittedly.

I have enquired in several contexts about this, and
even entymologists are very uncertain about exactly what the ants
are doing with the aphids in the UK[*], and in what proportion of
cases.
In my experience entymologists can't even agree on which pub to go to.
Seriously though, I have spent a number of hours with a beer watching them
on the plants and I've seen them moving aphids around in their jaws -
especially the apple tree, for some reason. They tend to pick them up at
the rear somehow or maybe by a leg - I can never quite see - and carry them
some distance to a seemingly random spot.

Unlike in the tropics, there is minimal evidence for much
in the way of shepherding, let alone farming - proof of association
(which, as you say, there is) is not even good evidence of causality.
True. I understand the distinction.

What there is no evidence for at all, and some evidence against,
is that killing ants helps to reduce aphid infestations. This is
pretty strong evidence that, if the protection actions occur, they
are not very effective.
That does seem to be the case. I'm hoping the blue tits nesting in the
apricot tree will polish off a few aphids for me.

Still they don't bother me much and don't seem to do any noticeable damage,
the biggest nuisance is them in the lawn.

[*] Except that the tabloids' usual innuendo is implausible.
Yuck! ;-)

--
Tim C.