Pine Processionary: Key Facts and Essential Information

The Pine Processionary is a fascinating yet harmful type of caterpillar that poses significant risks to both pine trees and humans. Belonging to the moth species Thaumetopoea pityocampa, these caterpillars can be identified by their striking appearance and peculiar nesting habits.

Known for their destructive feeding behavior, Pine Processionary caterpillars cause serious damage to various pine tree species. When these caterpillars feed on the needles of pine trees, the trees may struggle to recover from the damage, and in severe cases, it could even lead to tree death. Furthermore, they also pose potential health risks to humans and animals, as their hairs contain a toxin that can cause irritation and allergic reactions.

In this article, we will provide a comprehensive guide on the Pine Processionary caterpillar, including its life cycle, nesting habits, impact on pine trees, and the dangers it presents to people and animals. We will also discuss ways to identify, prevent, and manage infestations, ensuring that both our forests and our homes remain safe from these intriguing yet troublesome creatures.

Pine Processionary: Basic Understanding

Pine Processionary Caterpillars

Pine processionary caterpillars are a species of moth larvae known for their procession-like movement. They are found on pine trees and can cause defoliation, impacting the tree’s health and growth.

  • Common in Southern Europe and parts of Western Asia
  • Distinct procession-like behavior

These caterpillars can cause skin irritation and respiratory distress in humans and animals upon contact.

Pine Processionary Lifecycle

The pine processionary lifecycle is divided into several stages. Here’s a brief overview:

  1. Egg stage: Female moths lay eggs on pine needles during summer months.

  2. Larval stage (caterpillar): Eggs hatch into caterpillars that eat pine needles. They grow through several instars before spinning a communal cocoon, called a nest.

  3. Pupa stage: Within their silk nests, caterpillars transform into pupae, a stage that can last from weeks to months.

  4. Adult stage (moth): Adult moths emerge after the pupal stage, mate, and then lay eggs, completing the lifecycle.

Benefits of understanding lifecycle:

  • Helps in identification and control measures
  • Minimizes the impact on trees and human health

Comparison between Pine Processionary Caterpillars and Other Caterpillars:

Feature Pine Processionary Caterpillars Other Caterpillars
Habitats Pine trees Various plants and trees
Procession-like movement Yes No
Communal nests Yes No (except for some other species)
Adverse effects on human health Yes Some cause irritation, most don’t

In summary, the pine processionary is a distinctive moth species, whose larvae exhibit unique behavior and can impact both tree health and humans in proximity. Understanding their lifecycle can aid in identification and control measures.

Hazards and Impacts

Dangers to Humans

The Pine Processionary Caterpillar (Thaumetopoea pityocampa) poses a serious hazard to humans due to its stinging hairs that contain a toxic substance called thaumetopoein. Exposure to these hairs can cause:

  • Allergic reactions
  • Skin irritation and itching
  • Conjunctivitis (itchy, red eyes)
  • Respiratory problems

In extreme cases, some individuals may even experience anaphylactic shock. To minimize risks, avoid contact with their toxic hairs, nests, and be cautious around pine trees in the Mediterranean area, especially during the warm spring season.

Risks to Animals

Animals, particularly pets like dogs, are also at risk of suffering from Pine Processionary Caterpillar encounters. Dogs may experience:

  • Inflammation or necrosis due to biting or ingestion
  • Histamine reactions
  • Rash and itching

If your pet has been exposed, contact your veterinarian immediately for guidance and treatment. To protect your animals, make sure to:

  • Keep them away from nests and caterpillars
  • Monitor their behavior in pine tree areas

The following table compares the risks faced by humans and animals upon contact with Pine Processionary Caterpillars:

Risks Humans Animals
Allergic reactions Yes (from stinging hairs containing thaumetopoein) Yes (from ingestion or skin contact)
Skin irritation Yes (rash, itching, inflammation) Yes (rash, itching, inflammation)
Respiratory problems Possible (if toxin is inhaled) Less likely
Eye issues Conjunctivitis (itchy, red eyes)
Lethal outcomes Only in extreme cases of anaphylactic shock Necrosis or death (if not treated)

By being aware of these dangers and taking preventive measures, human and animal safety can be maintained.

Prevention and Management

Dealing with Pine Processionary Nests

Pine Processionary moth, Thaumetopoea pityocampa, causes defoliation to pine trees and may have harmful effects on humans and animals. One way to manage this pest is to remove the nests. Always wear protective clothing when dealing with nests. Nests can be removed by:

  • Cutting branches with nests
  • Use long pole with a hook to pull down nests

Natural Predators

Introducing natural predators can also help control Pine Processionary infestations. Some effective predators are:

  • Ants: Provide natural pest control services in forests
  • Wasps: Parasitize caterpillars, reducing their numbers
  • Bats: Eat moths, controlling the pest’s lifecycle

Comparison between predators:

Predator Benefits Drawbacks
Ants Continuous pest control May disturb other insects
Wasps Effective on caterpillars May sting humans and animals
Bats Control moths’ lifecycle May require specific habitat

Role of Local Authorities

Local authorities play a crucial role in managing Pine Processionary moth infestations by:

  • Monitoring wooded areas for infestations
  • Providing guidance on prevention and management
  • Organizing removal of nests when necessary
  • Supporting initiatives for natural predator introduction

Geographical Distribution and Adaptation

Pine Processionary in Europe

The Pine Processionary (Thaumetopoea pityocampa) is a moth species commonly found in the Mediterranean area. It is also prevalent in other European countries, including Spain, Portugal, and France. These moths have adapted to wooded areas with a preference for coniferous trees, such as pines.

Temperature and Habitat

Pine Processionaries thrive in cold to mild temperatures, usually in the spring season. Adaptations to their environment include their unique walking behavior, where caterpillars move in a processionary manner, forming long chains.

Comparison with Oak Processionary

Features Pine Processionary Oak Processionary
Preferred Host Trees Coniferous trees, such as pines Oak trees
Geographical Range Mediterranean area and some parts of Europe Europe and parts of Asia
Caterpillar Walking Processionary-style movement Processionary-style movement
Habitat Wooded areas Wooded areas

Key characteristics:

  • Europe native species
  • Caterpillars walk in a processionary manner
  • Prefer colder temperatures during spring

As the information indicates, the Pine Processionary is predominantly found in the Mediterranean area and other European countries. Their unique walking behavior and adaptation to colder temperatures in the spring season set them apart from other moth species.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Pine Processionary Caterpillars in Japan, we believe

 

Roving Japanese Caterpillar Gangs
Location: Noto Peninsula, Ishikawa, Japan
June 29, 2011 8:13 pm
I first noticed large gangs of these caterpillars in the tree near my apartment in rural Japan a few days ago. As of this morning, they’re on a mass exodus toward the house. I’ve turned the AC on to discourage exploration of the machine’s innards, but beyond that I’m not sure if I need to do anything about them or just let them be. Step one would be finding out what they are! Thanks a lot.
Signature: Brian

Pine Processionary Caterpillars on the March

Dear Brian,
We believe we have identified your Caterpillar aggregation as the Pine Processionary Caterpillar,
Thaumetopoea pityocampa.  According to the faculty web page of Cortland:  “The pine processionary caterpillar is the best known of all the processionaries, studied as early as 1736 by Raumier and later by Fabre (1898) whose essay “ The life of the caterpillar” is among the classics of popular entomological literature.  The insect is found in the warmer regions of southern Europe, the Near East, and North Africa.  It is the habit of the caterpillars to move over the ground in long head-to-tail processions and to sting with urticating hairs anyone who attempts to molest them that has brought the caterpillars to the attention of the public.  It is also one of the most destructive of forest insects, capable of defoliating vast tracts of pines during its episodic population surges.  Of interest here, however, is the fact that is among the most social of caterpillars.  Sibling groups stay together throughout the larvae stage, often pupating side by side at sites they reach by forming long, over-the-gound, head-to-tail processions.”  The Forests and Human Health website devoted to sources of dermatitis has information on a wider range for the Pine Processionary Caterpillars, and states:  “Processionary caterpillars, such as Thaumetopoea spp. and Ochrogaster spp., are not only important causes of forest damage, but have also caused frequent outbreaks of dermatitis, ocular lesions and allergic reactions in Australia, Europe, Japan and the United States (Diaz, 2005; Vega et al., 1999). The pine processionary caterpillar (Thaumetopoea pityocampa) can remain in the chrysalis stage for several years if environmental conditions are unfavourable. As a result, moths from several generations can emerge simultaneously when favourable conditions occur, causing severe outbreaks (Vega et al., 1999). Contact with dead larvae, cocoons, nests and debris from infested pine forests can also cause dermatitis throughout the year. During outbreaks in France, media campaigns have been conducted to warn the public away from affected areas. In Israel, T. pityocampa occurs in pine plantations and on urban trees and is considered a serious pest of medical importance causing eye problems and even temporary blindness (Solt and Mendel, 2002).  Pine processionary caterpillar, Thaumetopoea pityocampa, is a serious pest causing dermatitis epidemics and eye problems.”  Finally, this article entitled The Dangerous Pine Processionary Caterpillar provides additional information and precautions.

Pine Processionary Caterpillar

 

Letter 2 – Pine Processionary Moth Caterpillars

 

Subject: Caterpillar Procession
Location: Monte Verità, Ascona, Switzerland
May 24, 2013 1:57 am
Hi,
I photographed these caterpillars in mid-April at Monte Verita, in the hills above Ascona, Switzerland. The length of the caterpillar procession was around 6 feet. They were moving pretty quickly, clearing the path in under 10 minutes. It was a warm day, between 75 and 80 degrees, and one of the first warm days of the season in the area from what I was told.
Thought you might be interested. We love your site- thank you for all you do!!
Signature: Jennifer P.

Pine Processionary Moth Caterpillars
Pine Processionary Moth Caterpillars

Hi Jennifer,
Thanks so much for sending us your photos of the Pine Processionary Moth Caterpillars,
Thaumetopoea pityocampa.  According to the Wildlife in France website:  “In the spring, anytime from February until May, the caterpillars leave the trees and go down to the ground, this is when we will see them forming their long nose to tail processions as they make their way to find a place in the soil to pupate, the period of pupation can last a couple of months or several years. They actually touch each other to make a long chain, hence the common name of Pine processionary moth.”  The Pine Processionary Moth Caterpillars should not be handled because, according to the UK Forestry Commission website:  “caterpillars represent a public health hazard because they have thousands of hairs which contain an urticating, or irritating, protein called thaumetopoein. These hairs can be blown by the wind into contact with people and animals, resulting in painful skin irritations and rashes and, in some cases, allergic reactions in some people and animals.”

Pine Processionary Caterpillars
Pine Processionary Caterpillars

This must have been a very impressive procession to watch.

Pine Processionary Moth Caterpillars
Pine Processionary Moth Caterpillars


Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Pine Processionary Caterpillars in Japan, we believe

 

Roving Japanese Caterpillar Gangs
Location: Noto Peninsula, Ishikawa, Japan
June 29, 2011 8:13 pm
I first noticed large gangs of these caterpillars in the tree near my apartment in rural Japan a few days ago. As of this morning, they’re on a mass exodus toward the house. I’ve turned the AC on to discourage exploration of the machine’s innards, but beyond that I’m not sure if I need to do anything about them or just let them be. Step one would be finding out what they are! Thanks a lot.
Signature: Brian

Pine Processionary Caterpillars on the March

Dear Brian,
We believe we have identified your Caterpillar aggregation as the Pine Processionary Caterpillar,
Thaumetopoea pityocampa.  According to the faculty web page of Cortland:  “The pine processionary caterpillar is the best known of all the processionaries, studied as early as 1736 by Raumier and later by Fabre (1898) whose essay “ The life of the caterpillar” is among the classics of popular entomological literature.  The insect is found in the warmer regions of southern Europe, the Near East, and North Africa.  It is the habit of the caterpillars to move over the ground in long head-to-tail processions and to sting with urticating hairs anyone who attempts to molest them that has brought the caterpillars to the attention of the public.  It is also one of the most destructive of forest insects, capable of defoliating vast tracts of pines during its episodic population surges.  Of interest here, however, is the fact that is among the most social of caterpillars.  Sibling groups stay together throughout the larvae stage, often pupating side by side at sites they reach by forming long, over-the-gound, head-to-tail processions.”  The Forests and Human Health website devoted to sources of dermatitis has information on a wider range for the Pine Processionary Caterpillars, and states:  “Processionary caterpillars, such as Thaumetopoea spp. and Ochrogaster spp., are not only important causes of forest damage, but have also caused frequent outbreaks of dermatitis, ocular lesions and allergic reactions in Australia, Europe, Japan and the United States (Diaz, 2005; Vega et al., 1999). The pine processionary caterpillar (Thaumetopoea pityocampa) can remain in the chrysalis stage for several years if environmental conditions are unfavourable. As a result, moths from several generations can emerge simultaneously when favourable conditions occur, causing severe outbreaks (Vega et al., 1999). Contact with dead larvae, cocoons, nests and debris from infested pine forests can also cause dermatitis throughout the year. During outbreaks in France, media campaigns have been conducted to warn the public away from affected areas. In Israel, T. pityocampa occurs in pine plantations and on urban trees and is considered a serious pest of medical importance causing eye problems and even temporary blindness (Solt and Mendel, 2002).  Pine processionary caterpillar, Thaumetopoea pityocampa, is a serious pest causing dermatitis epidemics and eye problems.”  Finally, this article entitled The Dangerous Pine Processionary Caterpillar provides additional information and precautions.

Pine Processionary Caterpillar

 

Letter 2 – Pine Processionary Moth Caterpillars

 

Subject: Caterpillar Procession
Location: Monte Verità, Ascona, Switzerland
May 24, 2013 1:57 am
Hi,
I photographed these caterpillars in mid-April at Monte Verita, in the hills above Ascona, Switzerland. The length of the caterpillar procession was around 6 feet. They were moving pretty quickly, clearing the path in under 10 minutes. It was a warm day, between 75 and 80 degrees, and one of the first warm days of the season in the area from what I was told.
Thought you might be interested. We love your site- thank you for all you do!!
Signature: Jennifer P.

Pine Processionary Moth Caterpillars
Pine Processionary Moth Caterpillars

Hi Jennifer,
Thanks so much for sending us your photos of the Pine Processionary Moth Caterpillars,
Thaumetopoea pityocampa.  According to the Wildlife in France website:  “In the spring, anytime from February until May, the caterpillars leave the trees and go down to the ground, this is when we will see them forming their long nose to tail processions as they make their way to find a place in the soil to pupate, the period of pupation can last a couple of months or several years. They actually touch each other to make a long chain, hence the common name of Pine processionary moth.”  The Pine Processionary Moth Caterpillars should not be handled because, according to the UK Forestry Commission website:  “caterpillars represent a public health hazard because they have thousands of hairs which contain an urticating, or irritating, protein called thaumetopoein. These hairs can be blown by the wind into contact with people and animals, resulting in painful skin irritations and rashes and, in some cases, allergic reactions in some people and animals.”

Pine Processionary Caterpillars
Pine Processionary Caterpillars

This must have been a very impressive procession to watch.

Pine Processionary Moth Caterpillars
Pine Processionary Moth Caterpillars


Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Processionary Caterpillars from Australia

 

Subject: aussietrev Mass Migration
Location: Nth Burnett. Queensland Australia
December 24, 2012 6:25 pm
Hi guys,
These caterpillars have spent the past few days completely stripping a small wattle tree at the end of my carport. They live communally in a large web balls and leave the tree covered in web when they leave after consuming every single leaf.
This trail stretched over 9 metres in total and as each caterpillar is only around 10mm the count must have been well over a thousand individuals.
More information on this group at
http://www.brisbaneinsects.com/brisbane_notodontidmoths/THAUMETOPOEINAE.htm
Signature: Aussietrev

Processionary Caterpillars

Merry Christmas Trevor,
Thanks so much for providing these awesome images of Australian Processionary Caterpillars, in the Prominent Moth subfamily Thaumetopoeinae.

Processionary Caterpillars


Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

4 thoughts on “Pine Processionary: Key Facts and Essential Information”

  1. J. Henri Fabre, the famous French naturalist, wrote an entire book about these insects, Life of the Caterpillar, which is based on extensive observations and experiments on their habits. It’s a great read. Fabre’s books got me interested in entomology long ago.

    Reply
    • Thanks for the reading suggestion. We have a wonderful copy of Fabre’s book of insects in our own library, and it would make a very nice reread, but we are not familiar with his book on the Pine Processionary Moth Caterpillars.

      Reply
  2. i will like to know if theres any fancy caterpillars from arizona cause i live in arizona and i wanna know so can you plz reply

    Reply

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