Caterpillars out early

Every year, The Resident receives reports of animals and humans who have come into contact with the Processionary Caterpillar, a small grub which builds its nest in pine trees and which can cause skin rashes and irritation. It seems that this year, thanks to the mild weather, this local menace has hatched out a little early. At first glance, the caterpillars look like most others. In fact, they are mildly poisonous and can cause severe irritation to both humans and animals. Inquisitive dogs can end up with very swollen mouths and snouts and can even be at risk of death if they do not receive immediate treatment.

The Processionary Caterpillar is actually the larva of a type of silk producing moth, Thaumetopoeidae. The grubs live in large communal nests, know as ‘bagnests’, which hang from tree branches, most commonly in pine trees. When these voracious eaters have exhausted their current locations food supply, the caterpillars form a procession. The larvae’s spinneret, located in its mouth, produces a trail of silk as it walks, the next caterpillar hangs on to the silken trail, adding its own silky thread, and so a long procession is formed, sometimes containing 50 caterpillars. The long line of marching caterpillars appear harmless, but each grub is equipped with special hairs that have special glands at the base; these secrete a poison which, if it comes into contact with human or animal skin, can cause immense irritation.

The International School at Porches had a recent outbreak of Processionary Caterpillars. We spoke to the Headmaster, John Butterworth, who explained that people have to be very careful around these poisonous grubs. “Not long ago,” he told us, “we had a small procession forming in the teacher’s car park and heading towards the school. There are too many children running around to take any risks, so the maintenance department were called immediately.” Apparently, the only way to ensure the caterpillars are destroyed is to burn their nest, but, sometimes, even that is not enough. Local residents Chris and Jenny Hurst recently discovered 17 nests in just one pine tree in their back garden. “Over Christmas time,” Jenny told The Resident, “the whole family became covered in a very itchy, sore rash. We didn’t really know what it was, until one day, when we were in our garden, we noticed a whole collection of nests hanging from the trees.”

The Hursts set light to the infested branches, but the following morning they found that the fire had not penetrated the nests and the caterpillars were still alive. “We had to actually split the nests open and set fire to them again in order to destroy them,” explained Jenny.

The Processionary Caterpillar can be very harmful, particularly if you have young children, dogs or cats, so check any pine trees in your garden. The larvae are resilient and must be handled with care when attempting to destroy them.

Trees send children to hospital

In a separate incident, 12 children, between the ages of 11 and 16, from the EB 2,3 school in Ourique had to be taken to the local health centre, after they started to itch and complain that spots had appeared all over their bodies. According to the school’s head teacher, Cesaltina Basílio, the complaints started after the children finished their physical education classes. “The children had to go through some pine trees as part of an exercise and, shortly afterwards, they started to complain,” she explained.

A doctor from the health centre, Júlia Gonçalves, revealed that the children were not at risk and that it was only a minor allergy. “They were treated with antihistamines and went straight back to school. It was nothing to be worried about. But to avoid a recurrence, I suggest that the pine trees be cleared or cut down.”