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


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