Wednesday, 4 October 2006

Not so lonesome termite

I'm not so fond of termites in the garden but I love 'em out there. You know, a long, long way away from my house. (Which is all wood, so you can see my concern.)

Termites live just about everywhere there's vegetation but they are most conspicuous in the tropics, where several species build eye-catching mounds. The shape and location of these mounds vary with the species. Perhaps the most recognisable are the huge, knife-blade constructions of the magnetic termite (Amitermes spp.), which are orientated north – south.

I didn't see any magnetic termites on this trip to Far North Queensland but I saw several other species. Two types of high-rise mounds are abundant along the road from Herberton to Irvinebank. Although they look different, they're both built by Nasutitermes termites. One species (I think it's N. triodiae) assembles massive mounds in open woodland. After rain, they plaster extensions onto the mound, holding the sandy soil in place with spit and poo. (They have more in common with the builder of my home than I anticipated.)

The other species (possibly N. walkeri) slaps its mound together high up in trees. This makes them popular with kingfishers, which excavate the mounds to create a nest.

Like ants (to which they are not closely related), termites are divided into castes. Each caste has a specialised role. But unlike those of other social insects, members of the soldier caste don't defend the mound with savage bites. Nasutitermes soldiers squirt glue at attackers through a nozzle on the head. The secretion sticks down small predators. It also contains volatile chemicals that repel larger attackers. Had I thought of it at the time, I would have annoyed them to find out the effectiveness of their defence.


Sherryl said...

Termites seem to be invading Melbourne at a great rate of knots. And several councils are refusing to declare termite zones, even though the little blighters eat on regardless. Is the invasion a result of poisons like DDT being banned, so that what is available now is almost ineffective?

Snail said...

I haven't read enough about it to decide whether it's really a new phenomenon or whether we're just noticing it more.

Archicentre published a report this year based on their inspections (which might be biased towards the tattier and/or older houses, although they suggest that isn't the case) and found that there was a 9% infestation rate in the Melbourne region. The eastern suburbs suffered more---presumably because they're more humid and timbered than the western ones. (Although Newport was a termite hotspot as well.)

Houses should be built with termite protection but they're tough little buggers and will overcome most mechanical barriers in the long term. Poisons (most of which are truly bloody awful) become less effective over time anyway, either because they break down or because over-use ends up selecting for toxin-resistant pests. (That old arms race again.)

So, I dunno. And I haven't seen any termites at this place. But I'm a bit worried abou some sagging bearers. I hope its just movement due to the highly reactive clay in this neck of the woods ...