Wednesday, 8 September 2010

More clockwork

Last Thursday I predicted that parasitisation of the Nematus pavidus sawfly larvae would take place either on Monday or Tuesday. Monday was a complete washout, but sure enough yesterday saw the initial egg-laying taking place.

I need to set this next image in context. The leaf is now a bare skeleton and most larvae have moved to another leaf. A few are still left on the original leaf and the female Campodorus is busy making sure each one is parasitised.

She moves to the underside of the leaf and curls her abdomen round close to where the larvae are:

Then she moves her abdomen around in the direction of the larvae (you can just make out the stubby little ovipositor in this shot):

Her abdomen approaches the larva (I have no idea how she senses their position so accurately), and the larva attempts to make an avoiding manoeuvre:

But the stabbing move is made unerringly, and the parasitisation takes place:
The egg will now remain unhatched inside the sawfly larva until it pupates, at which time the Campodorus egg will hatch and the Campodorus larva will consume the contents of the pupa.

Unfortunately for the Campodorus, a certain Mesochorus hyperparasite has different ideas. Perhaps Thursday or Friday will enable me to show another twist in this saga.

Post-script: Whilst I was musing about the amazing similarity between the abdomen and an elephant's trunk, I thought I would look a bit more closely, and I wonder if the abdomen is fitted with sensors of some kind. A trawl through yesterday's images delivered this shot showing the ovipositor and what seems to be two holes. 'Nostrils', anyone?

1 comment:

Gill said...

What a fantastic sequence - and how incredibly fast those larvae have eaten the whole leaf! Incredible close-ups.

I love the idea of "nostrils" and suspect (a) you're dead right and (b) this may be a new discovery.