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Tent-Making Caterpillars

The western and sonoran tent caterpillars along with fall webworm and tiger moths are the four tent-making caterpillars that inhabit the state of Colorado.  The time frames in which these caterpillars create their tents vary from spring through mid-summer; however, a majority of the tents seen after mid-summer belong to fall webworms.  Although the silken shelters themselves rarely cause damage to the trees, the caterpillars that call the tents home may cause damage and even dieback or death of the tree as they consume foliage.  The most damage typically occurs with the western tent caterpillar which has been known to kill off large stands of Aspen trees.  In general however, it is the tent itself that creates the most attention to these caterpillars.  The tents are used for daytime shelter where they rest and shed their molted skins.  The caterpillars feed primarily at night.  Depending on the infesting species, tents are commonly found on aspen, chokecherry, gamble oak and cottonwood.  Single generations of these species are produced each year.  In addition to tent-making caterpillars, other insects create similar tent like masses including certain species of sawflies, pine webworms and uglynest caterpillars.  Control is typically by natural predators; however, contact and microbial insecticides are also available.