In certain wooded areas, it is common to notice silky structures draped over branches or clustered at the ends of twigs. These webs are not random, but carefully spun shelters created by groups of larvae as part of their survival strategy. The structures serve as protection from weather and predators, while also functioning as a central base from which the young insects emerge to feed before retreating again.
The webs can vary greatly in size, sometimes appearing as small, thin sheets, while in other cases stretching across entire sections of trees. Within these silken shelters, the larvae live communally, resting and conserving energy between feeding sessions. As they grow, the shelters are often expanded, gradually becoming more noticeable to observers. These large masses of silk may look alarming, but they are usually more unsightly than truly damaging to healthy trees.
Feeding takes place primarily on the leaves of the host plants, and the silk coverings act as both protection and a feeding chamber. In some species, the larvae stay within the web to eat, while in others they venture out in groups, leaving behind visible trails on the foliage. This coordinated feeding behavior can lead to significant defoliation during outbreak years, though many trees recover once the season passes.
Ecologically, these web-builders provide an important food source for birds, wasps, and other predators. The very shelters designed to protect them can also attract enemies that specialize in penetrating or exploiting the silk. Despite this, their ability to form large colonies ensures that at least some survive to adulthood, continuing the cycle each year. Their presence is thus both a natural part of forest dynamics and a signal of seasonal changes.
For humans, the sight of thick webs in ornamental or fruit-bearing trees can cause concern, especially in gardens and orchards. While infestations may affect yields or aesthetics, the long-term impact is usually limited unless outbreaks are severe.
Caterpillars that make web nests In Trees
Eastern Tent Caterpillar (Malacosoma americanum)
These caterpillars are among the most familiar web-builders in North America. They construct large silken tents in the forks of tree branches, often in cherry, apple, and other fruit trees. The tents serve as communal shelters where caterpillars retreat after foraging. Their webs grow larger as the colony expands, sometimes becoming highly visible and causing alarm despite usually not killing the host tree.
Forest Tent Caterpillar (Malacosoma disstria)
Unlike their eastern relatives, these do not make true tents but instead weave silken mats on tree trunks and branches. They are highly social, moving in processions and resting together on their woven sheets. They feed on a wide range of hardwoods, including aspen, oak, and maple, and can cause widespread defoliation during outbreak years.
Western Tent Caterpillar (Malacosoma californicum)
Found primarily in the western United States, these caterpillars form conspicuous silken tents in shrubs and trees, especially in chokecherry and willow. Their colonies expand the tents as they grow, using the structure for protection against predators and unfavorable weather. During population booms, they can strip host plants almost entirely of foliage.
Sonoran Tent Caterpillar (Malacosoma tigris)
This species inhabits desert and semi-desert regions, building protective silken tents in native trees like mesquite. Though less well-known than their eastern relatives, they play a similar ecological role, forming communal webs where they gather between feeding bouts. Their adaptations help them thrive in hotter, drier climates.
Fall Webworm (Hyphantria cunea)
Unlike tent caterpillars that build webs in branch crotches, fall webworms create massive silken nests at the ends of branches. They enclose leaves within these webs and feed inside, expanding the nest as they grow. They are generalist feeders, infesting over 100 tree species, and their webs can be unsightly, though usually not fatal to the host plant.
Western Tent Webworm (Malacosoma fragilis)
This species, found in certain western habitats, weaves communal webs in a variety of deciduous trees. The webs often appear thinner and more delicate than those of other tent caterpillars but still provide essential protection. Their life cycle and habits mirror those of closely related species in the same genus.
Spotted Tent Caterpillar (Malacosoma incurva)
This species is known for its web structures in certain regions of North America. Like others in its group, it uses silk to bind branches together into protective shelters. These webs provide a communal living space where caterpillars regulate their temperature and gain protection from predators.
Southwestern Tent Caterpillar (Malacosoma arizonense)
Native to southwestern areas, this species specializes in building silk tents in native hardwoods and fruit-bearing trees. Their webs are highly visible and provide safety against the intense sun and predators. Populations occasionally surge, leading to noticeable defoliation in local habitats.
Pacific Tent Caterpillar (Malacosoma constrictum)
Found on the Pacific coast, this species constructs large webs in deciduous trees and shrubs. Their colonies expand their tents daily, with the silk providing not only safety but also a communal resting area between feeding periods. They are important prey for many birds and parasitic wasps.
Large Maple Spanworm (Prochoerodes lineola)
While not a tent caterpillar, this looper species has been observed producing silken threads and sometimes creating light webbing on leaves and branches. Their silk functions more as a protective layer and less as a communal shelter, but they still contribute to the diversity of tree webbing insects.
Orchard Tent Caterpillar (Malacosoma orchestreum)
As its name suggests, this species favors orchards and builds protective silk tents in fruit trees such as apple, pear, and cherry. The webs expand as colonies grow, and infestations can affect orchard health. Despite their damage, they play a role in natural food chains as prey for birds and beneficial insects.
Texas Tent Caterpillar (Malacosoma texanum)
Native to Texas and nearby states, this species forms webs similar to those of its relatives but usually in local fruit-bearing and ornamental trees. Their silky nests are most often seen in the spring, when populations emerge in large groups, making them a notable seasonal presence in southern landscapes.