This guide explores in detail the life cycle of processionary caterpillars, insects known for their ability to create nuisances in green spaces. The information presented aims to provide an in-depth understanding of the different stages of development of these lepidoptera, thus making it possible to better anticipate and manage their presence.
The life cycle of processionary caterpillars of the pine, which is most common in Europe, begins with the laying of eggs by the female of the butterfly. These eggs are laid at the end of summer on the branches of pines and other conifers.
Laying Eggs
Egg laying is the first phase of the life cycle. A single female can lay up to 300 eggs, encapsulated in a protective silky structure stuck to pine needles. This usually happens between July and August.
Hatching Eggs
After about 30 to 40 days, the eggs hatch. The young caterpillars, very sociable, quickly begin to weave a community nest which serves as protection against predators and bad weather during the winter.
Larval phase
The larval phase is the longest and most visible of the cycle. THE processionary caterpillars go through several stages of growth, called instars. Each stage is characterized by a molt where the caterpillar sheds its exoskeleton to grow. This phase can last until spring.
Building the Nest
The nest, or tent, is essential for their survival during the winter months. Made from silks produced by the caterpillars, this nest thickens and widens as the larvae grow.
Procession and Burial
As spring approaches, the caterpillars leave the nest in a long procession on the ground to find a suitable place to bury themselves. This behavior is the origin of the name “processional”. Once a site is chosen, they burrow to begin the pupation phase.
Nymphosis
Underground, the caterpillars transform into chrysalises, remaining in this state of pupation for several weeks. The duration of this stage varies depending on climatic conditions and can influence the time of emergence of adult butterflies.
Emergence of Butterflies
The final phases see the butterflies emerge from the chrysalises to start the cycle again. Butterflies, having a very short adult lifespan, focus on reproduction to ensure the survival of the species. They do not feed and live just long enough to mate and lay eggs.
Detailed understanding of these phases is crucial for the ecological management of spaces affected by processionary caterpillars. It makes it possible to identify key moments to intervene effectively and in an environmentally friendly manner in order to control or prevent their proliferation.
