News

Ground nesting procesionary caterpillars are active and on the move. This period from March to June is known to be the high risk period of EAFL. It is time when caterpillars leave the nest and travel (up to 200 metres) to find a suitable place to rest underground (to pupate: developmental process to become a moth). Therefore, during this time the mares may accidentally ingest caterpillar setae (microscopic hairs) that are known to cause EAFL.

Caterpillars are usually well hidden in their nest. However, when they are at their last caterpillar stage (8th instar) they become more visible (see photo below). When you see ground nests where caterpillars are sitting on top of their frass (like the photo below), it is an indication that they will soon leave the nest.

For details on how to prevent EAFL please click here.

In the field, we have been dusting the caterpillars and inside the nest with fluorescent dust. This dust is non-toxic and it helps us track the movement of caterpillars.

Tree-hugger processionary caterpillars will remain in their nest longer than ground nesting forms. Therefore, the risk period of EAFL is approximately until end of June. Exuviae (shed exoskeleton), dead caterpillars and other nest material are often bursting out from the nest (see photo below) that is usually high up in the tree. These caterpillar remains may become airborne and dispersed further into the environment.
Please be cautious and do not stand underneath the nests.

 

The caterpillars are growing and are approximately at their 6th instar stage. Seeing a whole cohort of caterpillars outside its nest during the day like this (see photo below) is unusual, so we had to have a closer look!

The last post featured a parasitic Tachinid fly egg attached on the head of a caterpillar. This time, we found a different fly species laying 1st instar maggots directly on the caterpillar’s body! Some caterpillars were weak/immobile because a fly maggot was growing inside the caterpillar’s body. Once the maggot is ready to pupate, it bursts out of the caterpillar’s body and forms a pupa. After a few days, a fly will emerge from the pupa and the life cycle will restart.

On our last field trip, we found developing tree-hugger nests on the host tree, Corymbia tesserllaris. Tree-hugger nests look different to ground nests, they form a leathery skin on the tree trunk (see photo below).

Interestingly we found a couple of caterpillars above their nest which is unusual, since they rest inside the nest during the day. One caterpillar had a tachinid fly egg laid on its head (see photo below). Tachinid flies are parasitoids of processionary caterpillars, to read more about them click here.

Caterpillars are starting to hatch from egg masses and ground nests are starting to form.

Caterpillars from separate egg masses laid close together are likely to join to become one big nest (see photo below). This nest was formed from 3 egg masses. It is common to find egg masses/nests on previously infested host trees (you can tell by the caterpillar frass (poo) and shed exoskeleton surrounding/underneath the current nest).

We have also found a few cases of ground nesting caterpillar egg masses laid in the tree fork which is uncommon since they usually lay on the tree trunk (see photos below). This egg mass has successfully developed into a nest above ground!

 

Eggs have hatched and the processionary caterpillars are now at their second or third stage (instar). These stages feed during the day on their host tree so you may see them especially in the morning. Later stages feed at night.

 

Adult Bag-shelter moths (Ochrogaster lunifer) have been emerging from pupae during October and egg masses are starting to appear in areas where the moth is prevalent. There is 5 – 6 week window from egg lay to when the 2nd stage (instar) caterpillars start feeding in the tree canopy. Although only about half of the egg masses laid by female moths develop into caterpillar nests, this is a good time to remove any egg masses seen on properties that have the potential to cause problems later in the season. When removing egg masses observe all safety procautions including avoiding contact with skin and eyes, avoid breathing in the moth scales covering the eggs, do not remove in windy weather, and hypersensitive individuals should not attempt removal.

New images from the 2015/2016 caterpillar season are being added to this site from June 2016.