Contents: By Damage and Image
(In progress)
Contents: Alphabetical
alder flea beetle
aphid management
apple and thorn skeletonizer
apple ermine moth
ash whitefly New
azalea bark scale
azalea lace bug
azalea sawfly New
bark lice
Barypeithes root weevil Updated
Beneficial nematodes
biocontrol of root weevils
birch aphid Updated
black stem borer
bluegum psyllid
branch and twig borer
brown marmorated stink bug

bronze birch borer
boxwood leafminer
boxwood psyllid Updated
bulb flies
cabbage whitefly new
carpet beetle (images)
Calligraph californica

Ceanothus stem gall moth
cereal leaf beetle
cherry ermine moth
chilli thrips
cinnabar moth
clay colored weevil
cottony camellia scale
cypress tip moth

dogwood sawfly
Douglas fir sawfly
Douglas fir twig weevil
dustywings New
elm leafminer
European pine shoot moth
European wool carder bee
emerald ash borer
Fall webworm
flatheaded cedar borer
ground beetle gallery New
hollyhock weevil
honeylocust plant bug
honeylocust pod gall midge
Heliothis phloxiphaga
holly bud moth
huckleberry root aphids
ground mealybug
lacewings New
lady beetle gallery Updated
leaf weevil
light brown apple moth
maple aphids Updated
maple tip moth
maple midge
March flies Updated
mountain ash sawfly
Narcissus bulb fly Updated
Natural enemies gallery new
spruce twig aphid
oak ambrosia beetle
oak slug
obscure root weevil
Pacific flatheaded borer
peach tree borer
peach twig borer
pear blight beetle Updated
pear psylla
pear leaf-curling midge
pear sawfly
pine needle scale
pine and cone spittlebug New
poplar and willow borer
rose curculio weevil
rose midge
rove beetle gallery New
sequoia pitch moth
soldier beetle gallery New
snakefly gallery New
speckled green fruitworm
meadow spittlebug updated
tent caterpillars
viburnum leaf beetle
violet gall midge
western poplar clearwing
western spotted cucumber beetle
white pine weevil Updated
woolly ash aphid
woolly beech aphid Updated

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Western tent caterpillar

There are several subspecies of western tent caterpillar, Malacosoma californicum (Packard) (Lepidoptera: Lasiocampidae), M.californicum pluviale is found in the Pacific Northwest (Ciesla & Ragenovich, 2008).

The is a wide range of hosts for western tent caterpillar including red alder, crabapples, madrones, and roses.

In a central Oregon study of western tent caterpillar (Mitchell, 1990) there was one generation a year and they overwintered in the egg stage. Each female lays only one egg mass. Egg massess are found more commonly on the sunny side of trees. The eggs are laid together in a mass and covered with spumaline, a frothy substance that dries to a hard covering which protects the eggs from low temperatures and dessication. Egg hatch occured at 50 degree days. There were 5 larval stages. Dispersal of the caterpillars occurred around 300 degree days. Pupation began a week later (400 degree days). First moths occurred around 500 degree days. At 800 degree days (in July), peak moth flight was observed.

Outbreaks of tent caterpillars tend to be cyclic. Western tent caterpillars in southwestern British Columbia, Canada, were found to fluctuate in 6-11 year cycles (Myers, 2000).

Damage from western tent caterpillar is considered primarily aesthetic and not damaging the vitality of the trees. Chemical control is rarely recommended. Pruning off infested limbs can be done when they are within reach.

Biological control does occur with these caterpillars. Insect predators such as yellowjackets and parasitic wasps do attack tent caterpillars. Birds generally find the caterpillars repellent in flavor. Mortality and sublethal disease also occurs from a nuclear polyhedro virus (NPV).


Anon. 2011. Western Tent Caterpillar. Washington, DC: U.S. Department of Agriculture, Forest Service. Rocky Mountain Region. <11 March 2016>

Bentley, W.J., Day, K.R., and R.E. Rice. Tent Caterpillars. UC IPM Pest Management Guidelines: Plum. UC ANR Publication 3462

Brunner, J. 1993. Tent Caterpillars. Orchard Pest Management Online. Washington State University.

Carmona, Alejandro Segarra, and Pedro Barbosa. 1983. “Overwintering Egg Mass Adaptations of the Eastern Tent Caterpillar, Malacosoma Americanum (fab.) (lepidoptera: Lasiocampidae)”. Journal of the New York Entomological Society 91 (1). New York Entomological Society: 68–74. <18 March 2016>

Ciesla, W.M.; Ragenovich, I.R. 2008. Western tent caterpillar. Forest Insect and Disease Leaflet 119. Washington, DC: U.S.
Department of Agriculture, Forest Service. 8 p. <11 March 2016>

Mitchell, R. 1990. Seasonal History of the Western Tent Caterpillar (Lepidoptera: Lasiocampidae) on Bitterbrush and Currant in Central Oregon

Journal of Economic Entomology Aug 1990, 83 (4) 1492-1494; DOI: 10.1093/jee/83.4.1492

Myers, J. 2000. Population fluctuations of the western tent caterpillar in southwestern British Columbia. Popul Ecol (2000) 42:231–241. <18 March 2016>

Townsend, L. 2003. Checking Eastern Tent Caterpillar Egg Masses. UK Cooperative Extension Services. Entfact 449. <18 March 2016>




Orginal publication 8/12/07
Lastest revision <18 March 2016>

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University/NWREC.


Western tent caterpillars
Western tent caterpillars


Western tent caterpillar web

Western tent caterpillar egg mass
egg mass of western tent caterpillar

Western tent caterpillar egg mass
western tent caterpillar egg mass

Western tent caterpillar larvae, molted skins, and feces on their communal web
western tent caterpillar larvae, cast skins, and feces

Western tent caterpillar larvae
western tent caterpillar larvae

Forest tent caterpillar
forest tent caterpillar larva

Website editor:
Robin Rosetta

Page last modified 3/18/16


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