Bob Hack wrote about catching wasps:

> The regular traps are OK in spring to catch the queen wasps while they are
> still foraging. Each queen caught is one less colony in fall, right?

I used to think that way but, after the worst wasp year in living memory
last year, I have been involved in a trial of some commercial wasp traps
this year and have consequently learnt a great deal more about wasps and
traps!

Killing queens in the spring will make little difference to the overall wasp
population as only 9 out of 10,000 queens will successfully found a nest
(Social Wasps, Rentokil Library).

Wasps have two type of behaviour - hunting and foraging.  After nests have
been started in the spring, the wasps hunt for food for their larvae.  The
larvae are carnivorous, so the wasps will catch large numbers of pests and
are therefore beneficial at this time - we should not try to eliminate them
as they are part of the natural balance.  When the wasps feed the larvae,
they are rewarded with a drop of sweet liquid exuded by the larvae, so they
have no need to forage for themselves.

Later in the season, the nest reaches a peak and then starts to decline.  At
this point, there are less larvae to feed and consequently the large adult
population no longer has to hunt for insects - more importantly for us, it
has to find its own supply of sweet food.  The behaviour converts from
hunting to foraging.

According to my trap supplier, it is crucial that traps never allow any
wasps to escape as they will then recruit more to the food source.
Certainly that was my experience last year with simple bottle traps;
although I caught huge numbers of wasps, I could see that many did escape
and ever larger numbers kept coming.  So, according to the theory, a good
trap should catch all of the scout wasps and then there will not be a
problem.  It does seem to work - at one large visitor centre in the UK,
stinging incidents were reduced by 97% after installing the traps.

Of course, this year was not a good year for a trial!  The very long, cold,
dry spring hit the wasps very hard and delayed the build up of nests.  Here
in the Midlands we would normally expect wasps to convert from hunting to
foraging in early August, but this year they were still hunting in early
November.  Then the weather changed suddenly and I have not seen a single
wasp since the first frosts.  However, the traps did catch a fair number of
wasps and I have not had any wasps problem in the apiaries this year.  It is
interesting that the traps also caught large numbers of wax moths and flies.
More information on the traps is available here:
http://www.waspbane.co.uk/
Incidentally, the bait used is a mixture of Carling Black Label lager, a
small amount of either honey or maple syrup, and three secret ingredients.
For my own traps in the past I have always used plain sugar syrup - which
wasps can obviously smell easily.

Peter Edwards
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