An innocent line of caterpillars on the move in the area of pine trees may not appear dangerous. Be aware, however, that these harmless looking creatures can present a serious threat to humans, and most especially, to dogs and cats. The caterpillars should be avoided at all costs but if humans or animals come into contact with them, emergency treatment should be sought immediately.
What are Processionary Caterpillars (Thaumetopoea Pityocampa)?
In the adult phase they are a simple and unremarkable short lived moth which emerges in the summer and flies at night. The male and female mate and a single female then lays up to 300 tiny eggs which she attaches in a mass to a pine needle. Around one month later these eggs hatch into minute caterpillars.
In the autumn/fall they start to build a permanent white silky nest on the tip of a pine branch. These cocoons appear during the winter looking like white cotton balls or candyfloss. The caterpillars come out to feed at night thereby avoiding attack by birds and predatory wasps.
At the start of each year the nest will look grey and dirty as excrement collects at its base. Generally this stage happens in February and March but, depending on spring temperatures, it can begin in January and/or continue until April. This is when the caterpillars leave the nest to find soft soil to burrow into. This is the time they are most dangerous to people and to animals.
The colony follows a leader, nose to tail, in a long procession. These processions can vary greatly in length, depending on how many have survived to this final caterpillar stage. Up to 60 caterpillars, each about 3 – 4 cm long in a chain, is a remarkable sight and if seen along a track or road may be mistaken for a snake. While searching out a pupation site, they may travel a distance of 30 metres.
Once underground they change into pupae and lay dormant until the summer months when they then emerge as moths. If the weather conditions are not favourable, they may remain underground until the following year. This is why in some years there are many more visible nests as two years of moths have emerged at the same time. A similar danger comes from Oak Processionary Caterpillars.
Where are the Processional Caterpillars Found?
They are found in certain species of pine tree in many areas of the world. They are a particular hazard in the warmer parts of Southern Europe, North Africa, Australia, Japan and the United States. Milder winters have resulted in them expanding further north in Europe and they have been observed in England, Holland and Germany.
When are Pine Caterpillars Active?
The main months, in the Northern Hemisphere, are February and March although, depending upon geographical location and weather conditions, they can be seen as early as January and as late as April.
Why are the Processionary Caterpillars a Danger?
Each caterpillar has approximately 60,000 pointed defensive urticating (barbed) white hairs containing a toxin. They have been known to cause a severe itchy rash on humans that can last up to three weeks and can even cause temporary blindness and/or respiratory problems. A doctor should be consulted.
For dogs and cats the effects could be far more severe. If your cat or dog sniffs the hairs the result could be a severe allergic reaction, gangrene or anaphylactic shock, possibly resulting in death. The symptoms are excessive drooling, difficulty in breathing and/or white spots on the mouth or tongue. It is recommended that in these cases the animal’s mouth should be flushed out immediately with as much water as possible. Owners should try to avoid the animal’s toxic saliva, and seek emergency treatment from a vet.
How to Safeguard Pets
During the potentially dangerous months of late winter and early spring, try not to let dogs and cats roam free in areas with affected pine trees. Dogs are particularly susceptible as they are prone to sniff the ground and should be kept on a leash when walking in areas where the caterpillars are likely to be found.
What Should People Do to the Nests of the Caterpillars?
Nothing. Some farmers and landowners use poles to pull down the nests into metal buckets where they are then burnt. However, the nests will be full of the hairs which will be released when disturbed. Treading on the caterpillars will not destroy the toxic hairs and could result in these hairs being released into the air. Private individuals and members of local communities can, in the autumn/fall, seek professional assistance to spray the potentially pine trees in order to inhibit the growth of nests.
The Pine Processionary Caterpillars can be found in many parts of the world. They may be observed moving in long lines across the ground in the late winter and early spring and should be avoided at all costs by humans and their pets.
Martin Oldfield - Martin Oldfield I have worked as a Tour Leader taking groups of travellers to a range of countries in Asia, Africa, the Caribbean and ...
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