Wednesday, 11 March 2015

Sawfly larvae

The Old Weetangera Road - horse-drawn carts and coaches used to drive along here. 

Autumn is well and truly here now in Canberra, making great mornings to be out in the bush, and on the weekend I went for a walk along the old Weetangera Road through the Aranda Bushland Nature Reserve. The birds are now in their winter flocks, with roving packs of Pied currawongs ranging through the canopy searching for insects, and the various passerines were in mixed-species flocks, rolling and weaving through the shrubs and lower branches.

A ball of Sawfly larvae hang onto the stem of a eucalyptus sapling - follow the arrow

How the birds spot and catch insects so quickly is always fascinating to watch, but one insect that few birds can tackle are sawfly larvae. I noticed a ball of these lying up for the day on a sapling gum tree. These are a species of Perga sawfly larvae, they spend all day huddled together for protection, then a leader of the pack leads them to forage out on the eucalypt leaves at night. Like all sawflies, these are hymenoptera and related to bees, wasps and ants.

A knot of Sawfly larvae lie up for the day
- they seem to lie head to tail, probably for cautious defence -protected at both ends

Another defense strategy they use is to release a nasty fluid from their mouths, based on eucalypt oils. Although they are called spitfires for doing this, they don't actually spit the fluid, it just sort of oozes out. The tactic is effective though and few animals bother them. Except, for example cockatoos, the local Gang-gang Cockatoos will pick one at a time out of the bunch, chew them, lick out the juicy contents and spit out the spiny skins.

They use their pointed tails to tap on branches,
a simple means of communication to keep the group together when feeding

To read more on these amazing insects click here to access the Victoria Museum website.

No comments:

Post a Comment