March of the caterpillars

Planning an off-road excursion this spring to Portugal, Spain, Italy, Greece or even further south in North Africa? If you are, then you should be aware of a danger that not many people north of these regions will know about. 

The danger to which I refer is, on its own, barely 3cm long, but en mass can be 3 metres or more in length. This creature is the caterpillar of the Pine Processionary Moth (Thaumetopoea Pityocampa) … and it can be a killer!

Known colloquially as the Marching Caterpillar, the danger lies within its defence mechanism – tiny harpoon-like hairs that if touched can penetrate exposed skin resulting in an irritable rash. Importantly, they are coated in a fine dust that can also cause respiratory problems. Children and animals are particularly at risk.

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On the march – up to three hundred at a time.
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No caption required!

Many deaths of dogs have been recorded as they tend to collect the hairs on their paws, then lick them, thus transferring the hairs to their mouths. At this point the tongue can swell so badly, the only remedy is cutting the tongue before asphyxiation takes place, and even amputation in severe cases. In lesser cases, vomiting is more normal, it really depends on how many toxins are ingested. Too many, this can lead to kidney failure.

While children are not likely to suffer the worst effects, skin rashes and eye irritation are far more common, again something you really need to avoid. Yes, these cute-looking caterpillars are in fact nasty little critters!

But why are they known as Processionary or Marching Caterpillars? This is due to their life cycle. Once born from May to July, the adult moth only lives for one day, in which time it must mate and lay its eggs within the foliage of a pine tree. A single female can lay up to 300 miniscule eggs, whereupon it takes around a month for them to hatch. Once hatched, the minute caterpillars have five growth stages called ‘instars’. During their third moult or instar they build a nest resembling cotton wool, and continue to feed on the pine needles until the fifth instar. This usually occurs from February to April. At this point, the caterpillars walk down the trunk of their host tree to the ground in a long chain, before searching for the next place in their life cycle. It is this behaviour that gives them their name.

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Normally located at the very top top pine trees, the nests are strategically located to maximise solar energy to warm the occupants.
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Active throughout the winter months, observations obtained via infrared monitors show that colonies foraging in mountainous pine forests near Barcelona, Catalonia, leave their nests soon after sunset and travel to distant feeding sites located on the branches of the host tree. Here they feed overnight then return to the nest at dawn.
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Incredibly, these hardly caterpillars are even able to operate in sub-zero temperatures, before returning to the nest to warm up in the mid-winter sun.

As mentioned, these columns can be incredibly long (as many as three hundred individuals have been observed), hence become fascinating to children or animals who inadvertently stumble upon them. In fact these columns are actually searching for a new host tree at whose base they will burrow themselves just below the ground, whereupon they will form cocoons before the pupation state, before finally emerging as adult moths in early summer.

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The caterpillars are a distinctive orange-brown colour with blue bands running along their length … with of course a veritable arsenal of deadly hairs covering their entire upper half.

These caterpillars are also one of the most destructive of forest insects, capable of defoliating vast tracts of pines in their never-ending need to procreate. Even when they leave their nests, they still present a problem for it is advised not to not try to cut down the nests or burn them yourself as the hairs can become airborn. So bad is the problem, specialist exterminators are employed by communities to destroy their nests, as they still contain some of the hairs that the larvae leave behind. Yes, they are evil beyond belief! 

Catepillar9 - 278 size So be aware of the danger, for off-roaders are 100 times more likely to encounter these pests than everyday tourists who tend to stick to the beaches or cities.

You have been warned!

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Tom McGuigan