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Posted by portugalpress on March 02, 2015
Nests built like tents to provide perfect living conditions
The pine processionary caterpillars

It is that time of year again when the pine processionary caterpillars are on the move. If you have pine trees on your land or if you go out on walks near pine trees, you need to be extra vigilant.

They are one of the most destructive species of caterpillar to the pine trees in southern Europe, but there are now also reports of them being in the south of the UK.

They are a member of the Thaumetopoeidae family and are highly social. They start off by building shelters usually high up in the pine trees, spinning tent-like shelters out of silk within the branches.

These nests are built to provide perfect living conditions. They are positioned to maximise the sun’s rays. The caterpillars rest in the nests during the day, and the rise in temperature means that the food they have eaten during the previous night is easily digested.

These shelters appear to have no openings in them, and the caterpillars enter and exit by forcing their way through the many layers of silk. There can be several nests in just one tree. The bottom of these nests will fill with the faeces the caterpillars expel from their meals of the pine needles.

The normal cycle of life of the caterpillar is yearly. The moth of the caterpillar lays its eggs high up in the pine trees. These eggs are cylindrical in shape and covered in scales. The collection of eggs can be up to 5cm in length and they look extremely like the pine tree shoots, and can often be missed if you are looking for them.

When the larvae hatch, they go through five stages, eating the pine needles of the host tree as they grow. They have been seen here, already active for a few weeks. When they are ready to leave their nests, they form a line (where they get their name from) and head out to feast on the pine needles.

When they are ready to pupate, they head to the ground in their normal head-to-tail fashion. They have been seen to produce amazingly long lines and been mistaken for snakes by people who have not seen them before.

The larvae should never be approached, as they have hairs on their bodies that cause severe irritation to the skin. Older larvae can in fact eject the hairs a little like tiny harpoons if they feel threatened. These can cause severe respiratory distress if inhaled.

You need to make sure your dog does not go near these caterpillars, as the respiratory problems could be very severe. As we all know, dogs love to sniff at things they have not seen before and will try to nudge them to see what it is that’s moving in this way. If you suspect that your dog has come across a line of the caterpillars, then it is best to speak with your vet and ask their advice.

If your dog is prone to sensitive skin or respiratory problems, then you need to be extra vigilant. The caterpillars head to the soil at the base of the tree to find a site to pupate either on or just below the surface of the soil.

There are a few natural controls for these caterpillars but occasionally the only way to rid them from your trees is to use an insecticide. The natural way is always the best option but not always enough.

The famous Hoopoe we see here is rather partial to the pupae. The adult moth is a tasty treat for bats and the larvae appeals to birds such as the Great tit and the Great spotted cuckoo. Also the larvae can be affected by the horse fly and the processionary moth virus.

There are sprays available from good hardware stores that will kill any caterpillars that may have developed in the trees, but obviously if your dogs or cats go near these trees then spraying has to be done in a controlled manner.

Obviously, if you do wish to spray then do be vigilant for the caterpillars falling from the trees, as dogs and cats, and also children, like to have a little prod at things that look a little different.

I know that I have written about this before, but due to the horrific injuries these caterpillars can and do cause, it is one subject that cannot be written enough about.

Please do be extra vigilant and hopefully we will be able to have an injury-free time.

By Sue Ogden

Sue Ogden is a professional dog groomer living in the Algarve. In her regular column, she provides readers with information on how best to care for their pets. Trained in the UK, she studied nursing, breeding, grooming, nutrition and kennel management.