On 11 Aug 2004 12:51:09 GMT, (Nick Maclaren) wrote:


In article ,
Stephen Howard writes:
|
| I'm sorry - when did you conduct this other investigation? I've not
| seen a further post from you about this since your original one last
| year. I must have missed it - please post a reference to it.

I described it then, and referred to it this time.

The pattern of aphid infestations will be different, depending
on whether the aphids are spread from plant to plant by rain,
flying adults or ants. I have overserved the first two many times
and in many places, and have NEVER seen patterns compatible with
the last hypothesis.

In particular, because it is hard to tell transport by ants from
mobile juveniles, it indicates that most UK aphids of the types
that annoy gardeners most are not very mobile (as all the books
say). They are thus very different from mealybugs.

| How can it not be relevant?
| Please take me through this slowly again...
| The investigation was whether ants spread aphids, as in '(b)', yes?
| In carrying out this investigation you made no nocturnal observations
| ( unless you've repeated the investigation since )?

No. I have in SOME cases looked for nocturnal activity and not
found it. In particular, the common ants in my garden are fairly
strongly diurnal. I did, after your posting, check up and saw
no ants on aphids (or much elsewhere) at night.

Many ants in warmer climates are nocturnal, but the more common UK
ones seem to be diurnal. This probably has something to do with
temperatures, as they are also more active on warm days than on
cold ones.

| If you draw any conclusions from these observations without
| correlating ant behaviour, all you will have done is observed aphids -
| yes?

Yes. I have, however, also looked for correlations, but not in
this case.

| From your observations you're convinced that any nocturnal activity by
| the ants is insignificant in respect of the study?

No. From the nature of the study. And "orthogonal" not
"insignificant".

| Did your other studies make any discrimination between species?

Of ants or aphids? Yes. In particular, I was looking primarily
at black bean and brassica aphids, but looked at any infestations
that were dense enough and on regular enough plants to analyse
patterns.

I was referring to ants in this instance - but equally it's fair to
assume that the species of both aphid and plant has a part to play.

Thanks for the clarifications - my own garden ( in particular the veg
patch ) seems to be dominated by one of the Myrmicas , which form
significantly smaller colonies than other species in the garden and
seem to be almost vagrant in their tendencies.
From my observations ( and pains ) I've seen that they're far more
aggressive and territorial than L nigra and I'm currently studying the
relationship between aphid infestation and the species of 'host' ant -
though out of the 30 or so species we have in this neck of the woods,
these are the only two that I've seen hanging around with aphids in my
garden.

The 'golden opportunity' is to catch an aphid colony where the hosts
have been ousted, and then to observe any changes in the population.
Unfortunately this isn't at all easy to do!

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk