Picture: A Caterpillar Web In Trees
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.
Picture: A Dense Web of Caterpillar In Shrubs
Caterpillars that make web nests In Trees
Eastern Tent Caterpillar (Malacosoma americanum)
One of the most recognisable web-makers in North American woodland, the Eastern Tent Caterpillar constructs large, dense silken tents in the forks of wild cherry, apple, and crabapple trees every spring. The tent is not simply a shelter — it is a sophisticated thermal microhabitat. The caterpillars emerge in the morning to bask on the tent’s surface, raising their body temperature before venturing out to feed, then return to digest their meal in the warmth of the silk. The tent is enlarged progressively as the colony grows, and silk trails laid down by scouts act as pheromone-marked highways guiding the group to the best feeding sites. At peak infestation, a single colony can defoliate an entire tree. The caterpillars are dark with a white dorsal stripe and vivid blue spots along their sides. They become the Eastern Tent Moth, a modest, reddish-brown adult.
Forest Tent Caterpillar (Malacosoma disstria)
A close relative of the Eastern Tent Caterpillar, this species causes far greater ecological disruption across North American forests, periodically erupting in outbreaks that defoliate millions of hectares of aspen, oak, and sugar maple. Despite its name, the Forest Tent Caterpillar does not build a proper tent — it constructs a silk mat on tree trunks and large branches where the colony rests and baskets communally, rather than an enclosed structure. It is dark blue-black with a row of distinctive keyhole- or footprint-shaped white spots down its back — a reliable identification feature. Outbreaks occur on roughly ten-year cycles and, while dramatic in appearance, healthy trees usually recover by producing a second flush of leaves.
Lackey Moth Caterpillar (Malacosoma neustria)
The Lackey Moth caterpillar is the Old World counterpart of the tent caterpillars and equally conspicuous in its communal silk-weaving. Found across Europe, North Africa, and temperate Asia, it spins large silken tents in the branches of hawthorn, blackthorn, apple, and other fruit and hedgerow trees in spring. The tent serves as both a roosting site and a basking platform, and the colony follows pheromone trails to feeding areas each day before returning. The caterpillars are boldly striped in blue, orange, red, and white — classic aposematic colouration — though they are not significantly toxic. Infestations can be destructive in orchards and hedgerows. The adult moth is a drab reddish-brown with two pale diagonal lines across its forewings.
Western Tent Caterpillar (Malacosoma californicum)
The western North American representative of the tent caterpillar genus, this species builds silken tents in the forks of wild cherry, ceanothus, oak, and many other trees and shrubs across western Canada and the United States. Colouration varies considerably across its range — some populations are orange-brown, others are more brightly marked. Like its eastern relative, the colony uses the tent as a thermoregulatory base, emerging to feed and returning to rest and bask. It is an important prey species for many birds, including black-billed cuckoos, and outbreaks rarely persist for more than a few seasons before predator populations increase to suppress them.
Fall Webworm (Hyphantria cunea)
The Fall Webworm is native to North America but has spread widely across Europe and Asia, where it is considered an invasive pest. Unlike tent caterpillars, which build their webs in tree forks in spring, the Fall Webworm builds its web at the tips of branches in late summer and autumn, enclosing the foliage it intends to eat within the tent. The webs can be enormous — sometimes covering entire branch systems — and are loosely woven and untidy compared to the neat constructions of tent caterpillars. The caterpillars inside are pale yellow-green to dark, covered in long white hairs arising from dark tubercles. They feed on over 600 species of tree, making them exceptionally generalist. While unsightly, the late-season timing of their feeding means most trees suffer little lasting harm.
Pine Processionary Moth Caterpillar (Thaumetopoea pityocampa)
Found across southern Europe, the Middle East, and North Africa, the Pine Processionary is named for the remarkable nose-to-tail processions it forms when moving between feeding sites and the ground for pupation. The caterpillars live gregariously in large, conspicuous silken nests on pine and cedar trees, which act as communal shelters for the colony during the day and through cold periods. The nests are white and papery, often visible from a considerable distance on the upper branches of pines in winter. The caterpillars are covered in irritating urticating hairs that can cause severe skin rash, eye inflammation, and respiratory distress in humans and animals — dogs that investigate the processionary lines are particularly at risk of tongue and throat swelling.
Oak Processionary Moth Caterpillar (Thaumetopoea processionea)
A relative of the Pine Processionary but associated with oak woodland in central and western Europe, this caterpillar also builds large, silk nests on the trunks and branches of oak trees, from which it emerges at night to feed on foliage. Like its cousin, it produces urticating hairs — microscopic barbed shafts containing the protein thaumetopoein — that can cause significant health problems. The Oak Processionary has spread north and west in recent decades, reaching Britain where it is now an established and monitored pest in Greater London and surrounding counties. Management involves specialist removal of nests by protected workers wearing full protective equipment.
Buff-tip Moth Caterpillar (Phalera bucephala)
The Buff-tip Moth caterpillar is not primarily a web-spinner, but in its early instars the young colony spins a loose communal silk mat on the branch where they were hatched, feeding and resting together in a tight group. They are strikingly marked in yellow and black, and en masse on a branch they form a conspicuous, patterned mass. As they grow, they disperse and abandon communal silk-making, feeding individually on oak, lime, hazel, and many other deciduous trees. Large caterpillars can defoliate significant sections of a tree in a short time. The adult moth is a brilliant bark and broken-birch-twig mimic, one of the most convincing camouflage artists among British moths.
Small Eggar Moth Caterpillar (Eriogaster lanestris)
A close relative of the oak eggar, the Small Eggar is one of the earliest spring caterpillars in Europe, hatching in late winter when the hawthorn and blackthorn buds are just beginning to open. It lives in large communal silken webs that completely envelop sections of the host shrub, sometimes resembling tattered white bunting strung across a hedgerow. The caterpillars are dark and bristly, with orange-brown tufts, and the colony grows rapidly, the web expanding as they consume all foliage within reach. The adult female has rudimentary wings and cannot fly, laying her eggs in a ring around a twig, covered in scales from her abdomen for insulation.
Hawthorn Moth Caterpillar (Scythropia crataegella)
This small, pale grey caterpillar is a specialist feeder on hawthorn and spins a distinctive communal silken web over the developing leaf buds in early spring. The web is modest compared to the large tents of processionary or tent caterpillars, but groups of caterpillars inside can cause significant local defoliation of young growth. Found widely across Europe, it is a minor but noticeable pest of hawthorn hedges. As caterpillars mature, they disperse from the web and feed individually. The adult is a small, subtly patterned micro-moth.
Ermine Moth Caterpillars (Yponomeuta species)
The Ermine Moths comprise a genus of small moths whose caterpillars are notorious for producing vast, billowing silk webs that can envelop entire hedgerows, shrubs, and small trees in a ghostly white gauze. Different species specialise on different host plants — Yponomeuta malinellus attacks apple, Y. evonymellus attacks bird cherry, and Y. padellus favours hawthorn. Hundreds of small, pale caterpillars with black spots feed gregariously within the protective silk structure, stripping the host plant of its leaves while sheltered from most predators and parasitoids. Though the silk spectacle is dramatic and alarming, most plants recover fully once the caterpillars pupate and the webs dry out and fall away.
Brown-tail Moth Caterpillar (Euproctis chrysorrhoea)
The Brown-tail Moth caterpillar spends winter in a communal silken hibernaculum — a dense, tough tent spun at the tips of branches of hawthorn, blackthorn, and fruit trees. The tent serves purely as a winter refuge; in spring the caterpillars emerge, disperse across the tree, and feed individually. The caterpillars are dark brown with red spots and tufts of white hair, but it is their microscopic barbed setae that make them notorious — these hairs can cause severe skin rash, asthma attacks, and eye irritation in humans. Coastal populations in the UK and established colonies in New England can reach densities that trigger public health advisories.
Yellow-tail Moth Caterpillar (Euproctis similis)
Related to the Brown-tail, the Yellow-tail Moth caterpillar also constructs a communal silken web in which the colony overwinters. The web is built among the leaves and shoots of hawthorn, oak, and blackthorn and is less robust than that of the Brown-tail but serves the same protective function through cold months. The caterpillars are dark with red and white markings and carry urticating hairs, though their effect is generally milder than those of the Brown-tail. In spring the group disperses, and the caterpillars complete their growth individually. The adult female covers her egg batch with a tuft of yellow hairs from her tail.
Gum Leaf Skeletoniser (Uraba lugens)
Native to Australia, this caterpillar is a significant pest of eucalyptus trees, feeding gregariously in its early instars beneath a loose communal silk web on the surface of gum leaves. The young caterpillars skeletonise the leaf — consuming all tissue except the waxy cuticle — while sheltering under their silk. As they mature, they become solitary feeders and cause more significant defoliation. One of this species’ most remarkable features is that the caterpillar retains all of its shed head capsules from previous moults stacked on its head like a tower — a structure thought to deter parasitoid wasps or serve as a physical defence.
Spotted Apatelodes Caterpillar (Apatelodes torrefacta)
Found in deciduous forests of eastern North America, young Spotted Apatelodes caterpillars are gregarious and spin a loose communal silk mat on the leaves of ash, maple, cherry, and oak, feeding together before dispersing as they mature. The mature caterpillar is a dramatic sight — bright white or yellow with long, silky hair tufts and black pencil-tufts at each end, resembling a tiny, animated feather boa. Despite its striking appearance, it is entirely harmless. The adult moth is a subtly beautiful brown-and-white species.
Walnut Webworm (Acharia stimulea / Datana integerrima)
The Walnut Webworm caterpillar (Datana integerrima) produces conspicuous silken webs on walnut, butternut, and hickory trees in eastern North America. Early instar caterpillars feed gregariously within a loose web, consuming leaf tissue while the silk shelter protects them from some predators. They are dark brown to black with fine white lines along their length. A characteristic behaviour is their synchronised defensive posture — when disturbed, the whole group simultaneously arches its head and tail upward in a rigid C-shape, presenting a collectively intimidating display. As they mature, they feed without webbing.
Uglynest Caterpillar (Archips cerasivorana)
True to its name, the Uglynest Caterpillar produces one of the most untidy and visually striking silk structures found in trees — a large, messy nest of tied-together leaves, frass, silk, and shed skins on wild cherry and chokecherry trees. Colonies of yellowish-green caterpillars with dark heads live within this cluttered mass, feeding on the enclosed foliage. Found across much of North America, the nests are highly conspicuous and can cause the tips of heavily infested branches to appear completely brown and dead by midsummer. The adult is a small, mottled brown tortrix moth.
Pine Webworm (Tetralopha robustella)
Found across the eastern United States, the Pine Webworm caterpillar spins a dense, resin-studded silk tube among the needles of pine trees. Unlike the broad tents of tent caterpillars, the Pine Webworm’s nest is a tight, cylindrical structure packed with frass and dead needles that gives the infested branch tip a brown, matted appearance. The caterpillar itself is yellowish with dark longitudinal stripes. Infestations are most damaging on young pines and ornamental trees, where the loss of terminal shoots can affect the tree’s shape. The adult is a small pyralid moth.
Fall Cankerworm (Alsophila pometaria)
While not a web-maker in the true tent-caterpillar sense, the Fall Cankerworm caterpillar produces strands of silk as it feeds and moves through the canopy, and aggregations of caterpillars create a loose silk mesh over the foliage of elm, apple, maple, and oak. It feeds in spring despite its “fall” name — it overwinters as an egg laid in autumn, and the caterpillar hatches in concert with leaf-burst. The small, pale green or striped looper caterpillar can be present in astronomical numbers during outbreak years, and the silk threads they leave behind as they dangle from trees on the wind give infested woodland a gauzy, veiled appearance.
Lappet Moth Caterpillar (Gastropacha quercifolia)
A large and dramatic caterpillar found across Europe and temperate Asia, the Lappet Moth caterpillar is covered in dense, flat hair-tufts along its flanks that overlap like roof tiles or lappets — the feature that gives it its name. While older caterpillars are solitary feeders, young instars are gregarious and spin a communal silken web among the branches of hawthorn, blackthorn, sallow, and apple, resting and feeding together in the early weeks of their life. The web serves as both a shelter and a communal basking platform. The mature caterpillar is one of Europe’s most impressively camouflaged larvae, resembling a section of bark so convincingly that it is frequently overlooked.