I choose the thorns of the pines or the leaves of the oaks to feed me,
Who am I ?
I am particularly allergenic and stinging,
Who am I ?
You guessed it and it's already itching!
What if we set out to discover this complex and unfriendly insect ...
The processionary caterpillar
- It exists two kinds of processionary caterpillars, those that colonizepine trees (second choice fir) and those which colonize Oak trees.
- These caterpillars have a dark brown tint punctuated with reddish spots on the upper part of the flanks. Their belly is yellow and their head is black.
- Particularly hairy, the caterpillar has two kinds of hairs: silky white hairs and tiny orange, stinging hairs that develop in the third stage of their transformation.
- They feed on the thorns of the pine trees or the leaves of the oak trees that serve as their hosts. This defoliation slows down the growth of trees and weakens them.
The pine processionary caterpillar
- Larva of the moth, Thaumetopoea pityocampa of the order Lepidoptera, of the family Notodontidae. This 35-40mm butterfly is gray with black patterns and whitish spots.
- Formerly listed on the Mediterranean rim, caterpillars are now found in Normandy and in all regions of the North.
- Global warming contributes to this new distribution.
- The choice of trees to plant is another explanation. More and more black pines line highways, and Himalayan cedars (sold widely in garden centers) are chosen by municipalities for planting in cities.
The reproduction :
- In early summer, as night falls, the female sends out pheromones to alert the male to her presence within a 4 to 5 km radius.
- The male can travel between 25 and 50 km to find a female.
- After mating, the male dies.
- The female will lay her eggs in a pine or in a cedar. She died soon after.
From egg laying to adult stage:
- The eggs are deposited in rows of 150-300 eggs on twigs or pine needles where they form clumps.
- After 5 to 6 weeks, the eggs hatch and produce larvae. The caterpillars go through five stages before becoming butterflies, including three moults that will allow them to go from a few millimeters to a few centimeters.
- These transformations take place in different nests woven with silk threads, molt remains and excrement. Light in summer, dense in winter, they are easily spotted because they look like large balls of white cotton wool.
- In the spring, the caterpillars leave the pines to bury themselves underground in a sunny place. The procession is led by a female.
- Each caterpillar is wrapped in silk thread to build its cocoon.
- Then begins the stage of chrysalis: the caterpillar develops to become a butterfly or imago(adult insect).
- At the beginning of summer, the cycle can start again ...
The biological cycle of the caterpillar lasts one yearif the climatic conditions are favorable (temperature, humidity, thermal amplitude). Otherwise, the larva stops developing until better days arrive. This phase is called diapause. It can last for several years.
The caterpillar procession:
- They move by the hundred in a procession or perfect parade to build a new nest when the surroundings of their house no longer offer enough food or when they leave the tree to bury themselves in the ground.
- It is the contact of the head of the caterpillar with the hairs of the abdomen of the one before it that ensures perfect movement in single file.
- They follow a silk thread to find their nest.
- This procession becomes dangerous for humans and animals from the third larval instar of the caterpillars (see article on the dangers of the processionary caterpillar), because stinging hairs appear on the dorsal part of their abdominal segments.
The oak processionary caterpillar
- Larva of the butterfly Thaumetopoea processionea.
- It is found in Central Europe, Spain and Italy.
- In France, it abounds in Alsace, Burgundy, Ile de France, center, Poitou-Charentes and Midi-Pyrénées.
Differences from the pine caterpillar:
- Eggs hatch before oak buds appear.
- They are able to go without feeding (quiescence) until the oak leaves appear.
- They weave a stronger nest against the trunk or in the large branches of the Oak to undertake their pupation (period during which the caterpillar transforms to become a butterfly or imago).
Read more: Danger and treatment of the processionary caterpillar
To meditate : "What the caterpillar calls the end of the world, the Master calls a butterfly. "