In article ,
Stephen Howard writes:
|
| I put the word 'farm' in quotes for that reason - unlike the tropical
| species, ants here in the UK seem to have a less formal arrangement.

That is true.

| Anyone who's cast more than a cursory glance at a colony of aphids
| will have noted the interaction of ants. Furthermore, anyone who's
| watched ants attack prey will have noted a very distinct difference in
| both their attitude and posture when tending the aphids.

Also true.

| I suspect that the relationship is quite a complex one.
| For a start, adult ants themselves don't need to prey on the aphids
| for proteins, but the honeydew is a valuable source of food for them.
| Prey is required for the larvae though, and whilst ants will certainly
| use aphids it seems rather more likely that the ants take advantage of
| the fact that aphids attract much meatier prey in the form of their
| own predators - the aphid colony acts as a self sustaining booby trap.
|
| In effect, the ant acts as a middleman...or, dare I day, a pimp!

I have never seen that, and have some difficulty in believing that
it is true of Lasius niger.

| Well, my own experience in my veg plot has been that if there's a
| common black ant's nest ( Lasius niger? ) near the beans etc, then I
| find I have more problems with aphids.
| If I site the beans more to the centre of the patch ( whereby I can
| more readily spot an ant nest, and take appropriate action ) the beans
| seem to suffer far less problems with aphids.

I think that can tell you why that happens, and it is almost certainly
NOT due to the ants! Blackfly overwinter on other plants, such as
Viburnum and Philadelphus. They then breed asexually, develop
winged females, fly to summer hosts like broad beans and nasturtiums
and then breed asexually like mad.

It is probably because the flying females will alight on the outside
plants first.

I have been trying to control blackfly on beans by spraying infestations
on OTHER plants (mainly those two) as the beans grow, and it seems to
work.

| Given that there appears to be no formal herding of aphids, then yes,
| I wouldn't have thought that ants per se would increase the incidence
| of aphid colonization - merely take advantage of it and sustain it.

I haven't seen that, either, and have done a test or two.

| For an 'old wives tale' it seems to have a lot of credence out there
| in the bio-community - and I'd be thoroughly interested in any
| references you might have to work that throws a new light on this
| phenomenon.

I have no references, but have found no references to ANY evidence
that ants increase the infestations either. Not one. And I have
done a fair amount of enquiring.

Observation of ants fighting ladybird larvae (even if correctly
deduced) merely demonstrate that they can conflict. I have seen
Lasius niger climbing over ladybird larvae to milk aphids, and
neither interfering with each other.

I have observed the difference between aphid infestations with
ants and without, in the same row of broad beans and in more than
one location, and could see no difference in their vigour or
progress.

I have observed the pattern of aphid infestations in many places,
and have never seen any evidence of movement by ants. In all
cases, the colonies were probably due to flying females or rain
wash. The patterns are different in all three cases.

That is why I say that it is an old wive's tale. Like many such,
it has a lot of credence and some plausible arguments, but little
evidence.


Regards,
Nick Maclaren.