Saturday, 23 April 2016

Caterpillar Parade

The other day while walking up our driveway, I came across a group of Processionary Caterpillars.
From a distance, the caterpillars look like a moving snake.

 They are not attached to one another but apparently follow a pheromone trail laid down by the leader. Above shows the lead caterpillar. How the "leader" is determined is a good question. Occasionally something goes wrong and the caterpillars form a circle and the hopeless caterpillars circle about for hours until something causes them to diverge.

 The larger caterpillars are probably the females. A total of 53 caterpillars comprised this procession.

So what is happening here. The caterpillars live on acacia an other trees in large groups within clumps of webbing. When the caterpillars are mature, they leave the host tree and follow-the-leader to an area of soft, pliant soil where they bury themselves and form cocoons. After a period of time, the adult moths will emerge.
The adult, a moth Ochrogaster lunifer, family Notodontidae, subfamily Thaumetopoeinae. At this writing, the moths are not uncommon around lights after dark.

The fine hairs on the caterpillars are to be avoided. They are urticating can cause serious skin irritation and if there are accumulations of webbing, cast skins at the base of the host trees, these can provoke allergies in humans.

Dogs can come to grief by physically encountering the caterpillars. Should they step on the line or sniff the caterpillars, the hairs can become embedded in their paws or tongue when they lick the source of irritation. If the hairs remain embedded, and they often do, they can cause infection which in extreme cases can result in the tongue becoming necrotic and leading to amputation.


Denis Wilson said...

Amputated tongue sounds dreadful, DAVE.

Susan said...

We get a similar species in France, on pine trees. Pets will pick up the urticating hairs just by going out into the garden. The hairs rain down from the nests in the trees and come to rest in the pet's fur. A cat or dog licking themselves or a person picking the pet up will end up with the caterpillar hairs in their mouth or on their skin. It can be a real problem. The only solution is to cut the nest down and take a flame thrower to them or immerse for a week in a bucket of water. In both cases, wear eye protection and gloves whilst handling the nests.

Alice said...

OMG! Glad we don't have those in California.

Brolga said...

We have these annually on our farm in the Victorian Mallee. One year I made a study of the moths of which there were many. Not one moth had exactly the same pattern on its wings. They were all subtly different. That year we had a procession of more than 70 caterpillers wandering around for days. They made rather a mess by defoliating a lot of the local Cassias.