In article , Tim Tyler wrote:

Yes, I know perfectly well that the phenomenon occurs in the tropics,
and occasionally in the temperate zones. Even there, I doubt that
"ants are the aphids' friends", because it is probably that there
is more ant predation on aphids than ant protection of them. [...]

AFAICS, that doesn't seem to make sense :-(

Are you serious? Why on earth do you imagine that this particular
ecological association is constant over the whole earth, when no
other one is?

IMO, the ants are *farming* the aphids - in similar ways all over the
world.

Well, you are simply wrong. See any respectable book on entomology.
Michael Chinery "Insects", for example.

Just because the ants eat the aphids, that doesn't mean the aphids are
/not/ being farmed. You might just as well argue that humans are not
farming pigs because people have been observed to eat bacon.

No, it doesn't. But, as far as every reference that I have seen has
said, 'farming' ants are either absent from the UK or EXTREMELY rare,
and even ones that actively 'herd' aphids are not common.

The size of the UK makes it harder to find research on the ant-aphid
symbiosis which is demonstrably applicable.

Would you like to explain that? We have one of the largest and most
effective biological research communities in the world, an ecology
that supports God knows how many ants (but of only a few species),
and hundreds of species of aphids, many of economic importance
(thus meaning that a LOT of research has been done on them).

Here's a UK paper showing that the ants are defending the aphids:

``Soldiers effectively defend aphid colonies against predators in the field''

- http://calorierestriction.org/pmid/?n=9514674

At LAST! All right, that is evidence. More for my point than yours,
but it does include some evidence that at least one ant does protect
at least one aphid in the UK.

Of course, the family of aphids is a minor one in the UK and is not
the family that causes 95% of trouble to farmers and gardeners, and
the abstract says:

These observations provide the first demonstration that soldiers
are effective in defence against natural levels of predation under
field conditions.

Given the relative importance of the families, how much research do
you think will have found no evidence for this effect? Pemphigus
spyrothecae is an aphid that causes galls on poplar trees - NOT
something that is of any economic consequence. As I understand it,
the only relevant aphid in the UK in the Pemphigidae is woolly aphid
of apple trees, which is rarely even visited by ants in my experience.
Almost all of the problem ones are in the Aphididae.

...and here's a UK paper showing aphids produced more soldiers when ants
were not in attendance - which strongly suggests the ants were protecting
the aphids:

``Ant tending influences soldier production in a social aphid''

- http://calorierestriction.org/pmid/?n=11052537

I wasn't aware that there was a significant amount of either ginger
or storax either farmed or naturalised in the UK. The fact that the
authors are British doesn't mean that the ants are.

How I interpret what I see in my garden is ants farming aphids, by
protecting them, raising them, carrying them up to the tops of plants,
and using them as a technological tool to attack the plants, and steal
their juices - both by sucking the honeydew, and by eating the
resulting plump and juicy aphids.

I know you do. And I am pointing out that your interpretation is
prejudice, because you are using your observations to justify your
beliefs and not to check up on them. The evidence is all against
your interpretation being correct.

I fully expect the ant-aphid symbiosis to be global in extent and ancient
in origin.

Doubtless. The former is known to be not the case, however. See
above.

That doesn't /necessarily/ mean that the ants have an overall negative
influence on the plants the aphids prey on. The ants depend on keeping
the plants alive as well, and their farming may conceivably have
beneficial effects on the plants - as well as on the aphids that
feed on them - perhaps by deterring other predators.

That is one possibility.


Regards,
Nick Maclaren.