Picture: monarch butterfly
Butterfly caterpillars are the larval stage of butterflies, belonging to the order Lepidoptera. After hatching from eggs laid on host plants, their main purpose is to eat, grow, and store energy for the next stage of their life cycle. This stage is crucial for their development into adult butterflies.
These caterpillars typically have soft, elongated bodies divided into segments, with a distinct head and multiple legs. In addition to three pairs of true legs, they possess several fleshy prolegs that help them grip leaves and stems. Their appearance can vary widely, with some being smooth and green, while others are brightly colored or patterned.
Feeding is a major part of a butterfly caterpillar’s life. Most species are herbivores and feed on specific host plants, such as milkweed for monarch caterpillars. This close relationship with plants helps determine where adult butterflies lay their eggs, ensuring the young have immediate access to food.
As they grow, caterpillars shed their outer skin through a process called ecdysis. Each stage between molts is known as an instar, and with each one, the caterpillar increases in size and may even change color or markings.
Once fully grown, the caterpillar forms a chrysalis and enters the pupal stage. Inside this protective casing, it undergoes metamorphosis, transforming its body structure into that of an adult butterfly. This process can take days or weeks depending on the species.
Butterfly caterpillars are a key food source for birds and other animals, while also contributing to plant population control. Despite occasionally being seen as garden pests, they are essential for maintaining biodiversity and supporting the life cycle of butterflies.
Picture: Spicebush Swallowtail Butterfly
Butterfly caterpillars
Monarch Caterpillar (Danaus plexippus)
One of the most recognisable caterpillars in the world, the Monarch is banded in bold stripes of yellow, black, and white. It feeds exclusively on milkweed, absorbing toxic cardenolides that make both the caterpillar and the adult butterfly unpalatable to predators. It grows through five instars before forming its iconic jade-green chrysalis speckled with gold.
Painted Lady Caterpillar (Vanessa cardui)
This spiny, dark-coloured caterpillar is covered in branched black spines and displays yellowish lateral stripes along its sides. It builds a silken tent on its host plant — most commonly thistles — and feeds within this shelter. Found on every continent except Antarctica, it eventually gives rise to one of the world’s most widespread butterflies.
Black Swallowtail Caterpillar (Papilio polyxenes)
Young instars mimic bird droppings — brown and white — as camouflage. Later instars transform into plump, bright green caterpillars with black bands dotted with yellow spots. When threatened, it everts an orange forked organ called an osmeterium that releases a foul smell. It feeds on plants in the carrot family, including parsley and dill.
Eastern Tiger Swallowtail Caterpillar (Papilio glaucus)
This caterpillar is a master of deception. Early instars resemble bird droppings, while mature caterpillars are vivid green with large, false eyespots near the head to mimic a snake. It feeds on cherry, tulip tree, and ash, and the eyespots are convincingly detailed, complete with a shiny, pupil-like spot.
Cabbage White Caterpillar (Pieris rapae)
Slender and velvety green, this caterpillar blends almost perfectly with the leaves of cabbages, kale, and other brassicas it feeds upon. A faint yellowish stripe runs along its back. It is one of the most common garden caterpillars in the Northern Hemisphere and is considered a pest by farmers due to its voracious appetite.
Red Admiral Caterpillar (Vanessa atalanta)
Dark and bristly, this caterpillar ranges from black to greenish-grey, adorned with rows of yellowish spines along its sides. It feeds almost exclusively on stinging nettles and is a solitary creature that folds leaves around itself with silk to form a protective tent. The striking red and black adult butterfly emerges after pupation.
Common Blue Caterpillar (Polyommatus icarus)
A small, woodlouse-shaped caterpillar coloured bright green with a dark dorsal stripe and pale yellow side stripes. It feeds on bird’s-foot trefoil and other legumes, and has a fascinating relationship with ants, which tend to it in exchange for a sugary secretion it produces from a special gland.
Spicebush Swallowtail Caterpillar (Papilio troilus)
Perhaps one of nature’s most theatrical caterpillars, the mature form is bright green with two enormous, realistic false eyespots on its thorax that give it the appearance of a small snake. Early instars, by contrast, look like bird droppings. It feeds on spicebush and sassafras, resting inside rolled leaves during the day.
Giant Swallowtail Caterpillar (Papilio cresphontes)
Known to gardeners as the “orange dog,” this caterpillar is a convincing mimic of bird droppings — mottled brown and cream with a texture that resembles freshly deposited waste. It feeds on citrus trees and rue, deploying its osmeterium when disturbed. It is the caterpillar of North America’s largest butterfly.
Zebra Longwing Caterpillar (Heliconius charithonia)
White with black spots and long black spines branching from its body, this caterpillar is unmistakable. It feeds exclusively on passionflower vines, sequestering toxic compounds that persist into adulthood. The Zebra Longwing butterfly is unique in being able to digest pollen, and its slow, deliberate lifestyle begins here in the larval stage.
Gulf Fritillary Caterpillar (Agraulis vanillae)
Bright orange with rows of long, black branching spines, this dramatic caterpillar is a feast for the eyes — and a warning to predators. It feeds on passionflower vines, incorporating the plant’s toxins into its own tissues. Despite its fearsome appearance, the spines are soft and harmless to humans.
Question Mark Caterpillar (Polygonia interrogationis)
This caterpillar is covered in rows of orange and black branching spines, giving it a bristly, formidable look. It feeds on elm, hackberry, and nettles, sometimes gathering in loose groups on the same plant. The adult butterfly bears a silver question-mark-shaped marking on its hindwing — a detail traceable, poetically, to this spiny beginning.
Mourning Cloak Caterpillar (Nymphalis antiopa)
Jet black with a row of red-orange spots down its back and covered in branching black spines, this is a striking larva that feeds gregariously on willows, elms, and hackberry. Groups of caterpillars move together in processions, a behaviour thought to enhance their intimidating appearance to potential predators.
Viceroy Caterpillar (Limenitis archippus)
This caterpillar cleverly mimics a bird dropping, its body mottled in olive-brown, white, and cream tones. A small hump and two horn-like protuberances near the head complete the illusion. It feeds on willow and poplar, overwintering as a tiny larva inside a rolled leaf tube secured with silk. The adult is famous for mimicking the toxic Monarch butterfly.
Pipevine Swallowtail Caterpillar (Battus philenor)
Deep reddish-brown to almost black, this caterpillar is adorned with rows of fleshy, brightly coloured tubercles — orange or red — that signal its toxicity. It feeds exclusively on pipevine plants, accumulating aristolochic acids that make it, and the butterfly it becomes, poisonous. Many other butterflies mimic the adult’s iridescent blue colouration.
Zebra Swallowtail Caterpillar (Eurytides marcellus)
Pale green with yellow and black banding near the head, this elegant caterpillar feeds solely on pawpaw trees. It is found in moist, forested areas where pawpaw grows along stream banks. Resting in plain sight on leaves, it relies on its colour to blend with the dappled light of the forest understorey.
Cloudless Sulphur Caterpillar (Phoebis sennae)
This caterpillar varies in colour from yellow to green, with a lateral yellow stripe and small blue-black spots. It feeds on senna plants and is particularly active during migration seasons in the southern United States. Its bright yellow adult butterfly is a familiar sight in open fields and gardens.
Brimstone Caterpillar (Gonepteryx rhamni)
Smooth, pale green, and highly cryptic, this caterpillar lies flat along the midrib of buckthorn or alder buckthorn leaves, aligning its body with the leaf’s central vein. It is extraordinarily well camouflaged and extremely difficult to spot. The adult Brimstone is celebrated as one of the first butterflies to appear in European spring.
Peacock Butterfly Caterpillar (Aglais io)
Velvety black with rows of white dots and branching black spines, the Peacock caterpillar is a gregarious species, feeding communally on stinging nettles in a silken web. The young larvae remain together in a tight group for warmth and protection, only dispersing as they reach their final instar.
Small Tortoiseshell Caterpillar (Aglais urticae)
Another nettles specialist, this caterpillar is dark and spiny, with yellowish-green markings and rows of branched black spines. Groups of young larvae spin communal webs over the tops of nettle patches, basking in the sun to raise their body temperature. They are an incredibly common and beloved sight in European gardens.
Orange Tip Caterpillar (Anthocharis cardamines)
Long, slender, and pale bluish-green, with white sides and a dark dorsal stripe, this caterpillar is perfectly camouflaged on the seed pods of garlic mustard and lady’s smock. It feeds along the pods themselves, and if two caterpillars meet, the larger will often cannibalise the smaller — the pods cannot support more than one.
Purple Emperor Caterpillar (Apatura iris)
Cryptic and extraordinary, this bright green caterpillar bears two yellow-tipped horns on its head and a pattern of diagonal yellow-green lines that mimic a sallow leaf perfectly. It feeds on goat willow and grey willow, resting on leaf surfaces with its body aligned with the leaf’s midrib. One of Britain’s most prized butterflies begins this way.
White Admiral Caterpillar (Limenitis arthemis)
This caterpillar is mottled in brown and green, with warty tubercles along its back that give it an irregular, bark-like texture — excellent camouflage on woody stems. It feeds on honeysuckle and overwinters in a hibernaculum made from a rolled leaf. The adult butterfly has striking white-banded wings.
Silver-washed Fritillary Caterpillar (Argynnis paphia)
Dark and velvety with rows of long yellowish spines and a pale dorsal stripe, this caterpillar hatches in late summer and immediately enters hibernation before it has even eaten. Come spring, it seeks out violet plants, its sole food source, and feeds nocturnally to avoid predation.
Marsh Fritillary Caterpillar (Euphydryas aurinia)
Gregarious and conspicuous, this caterpillar is jet black with rows of white spots and stiff black spines. Groups of larvae spin communal silken webs over devil’s bit scabious, their primary food plant, and bask together in the sun. As they grow, the groups disperse. It is one of Europe’s most threatened butterfly species.
Comma Caterpillar (Polygonia c-album)
Dark brown at the head and bright orange-white towards the tail, this caterpillar uses countershading to create a broken outline that is difficult for predators to detect against the sky. It feeds on nettles, hop, and elm, and rests on the upper surface of leaves. The adult is famous for its ragged, leaf-like wing margins.
Large White Caterpillar (Pieris brassicae)
Pale yellow-green with black spots and a faint yellow lateral stripe, this caterpillar is a gregarious pest of brassica crops — cabbage, broccoli, and kale. Young larvae feed together in groups, while older ones disperse. The caterpillars are parasitised by Cotesia glomerata wasps, which lay their eggs inside the living larvae.
Green Hairstreak Caterpillar (Callophrys rubi)
Small, slug-shaped, and bright green with pale diagonal streaks along its sides, this caterpillar feeds on gorse, broom, rock-rose, and various other plants. Its woodlouse-like shape and green colouration render it nearly invisible among foliage. It too is attended by ants, which harvest a sugary secretion from its dorsal gland.
Holly Blue Caterpillar (Celastrina argiolus)
A small, flattened, and pale green caterpillar with a faint yellowish stripe, it feeds on the flowers and developing fruits of holly in spring and ivy in summer. It produces a honeydew secretion that attracts ants. The Holly Blue is unusual in alternating between two different host plants across two generations per year.
Small Copper Caterpillar (Lycaena phlaeas)
A tiny, bright green caterpillar with a subtle pink dorsal stripe, it feeds on sorrel and dock plants. Its flat body and brilliant green camouflage it perfectly among the leaves. Despite its small size and modest appearance, it develops into one of the most vivid and jewel-like butterflies of the European meadow.
Anise Swallowtail Caterpillar (Papilio zelicaon)
This caterpillar progresses through dramatic changes of appearance across its instars. Early forms resemble bird droppings; mature caterpillars are bright green with black bands dotted with orange spots. It feeds on plants in the carrot family, including fennel, anise, and wild parsley, and is common in western North America.
Pale Swallowtail Caterpillar (Papilio eurymedon)
Similar in structure to other swallowtail larvae, this caterpillar is green with a series of yellow and black eyespots along its sides and a pair of false eyes near its head. It feeds on buckthorn and coffeeberry. Found in the western United States, it is named for the pale, creamy-white colouration of the adult butterfly.
Two-tailed Swallowtail Caterpillar (Papilio multicaudata)
Stout and green, this caterpillar bears conspicuous false eyespots on its thorax that mimic the eyes of a small vertebrate. It feeds on ash, hoptree, and chokecherry. The adult butterfly, which sports two tails on each hindwing, is the largest butterfly found in much of the American West.
Western Tiger Swallowtail Caterpillar (Papilio rutulus)
Green and smooth with striking blue and yellow eyespots, this caterpillar rests in a rolled leaf shelter during the day and emerges to feed at night. It consumes the foliage of willows, cottonwoods, and alder. The eyespots serve to deter birds by mimicking the eyes of a much larger animal.
Canadian Tiger Swallowtail Caterpillar (Papilio canadensis)
A northern counterpart to the Eastern Tiger Swallowtail, this caterpillar is smooth and green with a pair of large eyespots. It feeds on aspen, birch, and cherry in boreal forests across Canada and the northern United States. It produces only a single generation per year due to the short northern summer.
Orange Sulphur Caterpillar (Colias eurytheme)
Slender and pale green with a whitish lateral stripe edged in darker green, this caterpillar blends perfectly into alfalfa and clover foliage. It feeds slowly and methodically, moving little between meals. It is the caterpillar of the familiar “Alfalfa butterfly” or “Orange Sulphur,” abundant in open fields across North America.
Cloudless Giant Sulphur Caterpillar (Phoebis agarithe)
Green or yellow with black spots and a pale lateral stripe, this caterpillar feeds on cassia and senna plants in tropical and subtropical regions. It is found across Central America and the Caribbean, extending into southern Florida and Texas. The adult is a large, vivid yellow butterfly.
Gulf Coast Buckeye Caterpillar (Junonia genoveva)
Spiny and dark, banded with orange and black, this caterpillar feeds on plantain and snapdragon-family plants in coastal and tropical habitats. It bears a strong resemblance to its relative the Common Buckeye caterpillar but is associated with warmer, more humid environments along the Gulf of Mexico.
Common Buckeye Caterpillar (Junonia coenia)
Dark blue-black with rows of orange spots and bristling with forked black spines, this caterpillar feeds on plantain, snapdragon, and toadflax. Despite its menacing appearance, the spines are harmless. The adult butterfly has stunning eyespot patterns on its wings, which are used to startle and confuse predators.
American Snout Caterpillar (Libytheana carinenta)
This caterpillar is slender and green with subtle yellow side stripes, blending into hackberry foliage, its primary food source. It is one of the more unremarkable-looking caterpillars, but the adult butterfly is memorable for its elongated “snout” — actually its mouthparts — which resembles a dead leaf’s petiole.
Gray Hairstreak Caterpillar (Strymon melinus)
A short, compact, slug-shaped caterpillar that ranges from green to pinkish, depending on the host plant — it is generalist, feeding on beans, cotton, mallow, and many other plants. It has a honeydew gland and is frequently tended by ants. It is one of the most widespread hairstreak butterflies in North America.
Eastern Tailed-Blue Caterpillar (Cupido comyntas)
Tiny and woodlouse-shaped, this caterpillar is green to yellowish with a faint dark stripe along the back. It feeds on the flowers and seeds of clovers and vetches, often burrowing into the flower head. Like other lycaenid larvae, it is associated with ants and produces secretions that encourage tending behaviour.
Spring Azure Caterpillar (Celastrina ladon)
Small and pale green to pinkish, this caterpillar feeds on the flowers and fruits of dogwood, blueberry, and wild cherry. It is one of the earliest caterpillars to appear in spring, timing its emergence with the flowering of its host plants. Ants frequently attend it, drawn to its dorsal nectary organ.
Harvester Caterpillar (Feniseca tarquinius)
Unique among North American butterflies, the Harvester is the only carnivorous species. Its caterpillar feeds exclusively on woolly aphids, camouflaging itself among the aphid colonies by covering its body with their waxy secretions and remains. Found near alder and beech trees where aphid colonies thrive, it is a remarkable evolutionary curiosity.
Silvery Blue Caterpillar (Glaucopsyche lygdamus)
A small, flattened, green caterpillar that feeds on the flowers and seeds of lupines and vetches. Like other blues, it produces secretions for attending ants. It is associated with open, flower-rich habitats including meadows, clearings, and roadsides, and is one of the earliest blue butterflies to appear in western North America.
Acmon Blue Caterpillar (Plebejus acmon)
Green and slug-like, this small caterpillar feeds on buckwheat and deerweed in western North America. It is attended by ants and hides during the heat of the day, feeding primarily in the cool morning hours. The adult male butterfly has a brilliant blue upperside, while the female is predominantly brown.
Karner Blue Caterpillar (Plebejus melissa samuelis)
An endangered subspecies, this small green caterpillar feeds exclusively on wild blue lupine. Loss of its habitat — oak savannas and pine barrens — has made it critically rare. Conservation efforts focus on maintaining open lupine-rich habitats, and the caterpillar’s survival is inextricably linked to that of its single host plant.
Meadow Brown Caterpillar (Maniola jurtina)
Pale green and hairy, this caterpillar feeds nocturnally on grasses such as fescues and bents, hiding at the base of grass clumps during the day. It overwinters as a small larva and completes its growth in spring. One of the most abundant butterfly species in European grasslands, it begins life in remarkable anonymity.
Gatekeeper Caterpillar (Pyronia tithonus)
Pale green and finely hairy, this caterpillar feeds on fine-leaved grasses in hedgerows and woodland edges. Like the Meadow Brown, it feeds at night and rests concealed in vegetation during the day. Its slender, cryptic form is entirely suited to life among grass blades, where it is virtually invisible.
Ringlet Caterpillar (Aphantopus hyperantus)
Straw-coloured or pale brown, this caterpillar feeds on grasses including cock’s-foot and couch grass. It overwinters twice before pupating — one of the slower-developing British butterfly caterpillars. It inhabits damp meadows, woodland rides, and hedgerows, emerging as a subtly beautiful dark brown butterfly.
Marbled White Caterpillar (Melanargia galathea)
Pale yellowish-green with a dark dorsal stripe and a forked tail, this slender caterpillar feeds on red fescue and other grasses. It is notable for feeding from the tip of grass blades downwards — the reverse of most other grass-feeding caterpillars. It overwinters while still tiny, completing most of its growth in spring.
Chalkhill Blue Caterpillar (Polyommatus coridon)
A short, green, woodlouse-shaped caterpillar with a dark dorsal stripe and pale sides, it feeds on horseshoe vetch in chalk downland habitats. It is attended by several species of ant, which protect it from parasitoids in exchange for honeydew. The adult male is a striking pale sky-blue.
Adonis Blue Caterpillar (Polyommatus bellargus)
Almost identical in shape to the Chalkhill Blue caterpillar, this green larva is also dependent on horseshoe vetch and chalk downland. It is more strictly ant-dependent, often being carried by ants into their nests for protection. The adult male displays an extraordinarily vivid electric blue that is considered one of the most striking colours in the butterfly world.
Silver-studded Blue Caterpillar (Plebejus argus)
Small and pale green, this caterpillar feeds on heather, gorse, and bird’s-foot trefoil on heathland and downland. Its relationship with black ants (Lasius niger) is obligate — the ants carry newly hatched larvae into their nests, tending them underground, then escort them to feeding plants each morning.
Dingy Skipper Caterpillar (Erynnis tages)
This caterpillar is pale green with a darker dorsal stripe and a dark head, feeding on bird’s-foot trefoil. It lives inside a folded-leaf tent secured with silk and is secretive and difficult to find. Despite its unremarkable larval appearance, it develops into one of the most moth-like of European butterflies.
Grizzled Skipper Caterpillar (Pyrgus malvae)
Pale green with a darker dorsal stripe, this caterpillar feeds on wild strawberry, cinquefoils, and agrimony. It constructs shelters by folding or rolling leaves with silk and feeds within them. It is associated with early-successional habitats with short, broken vegetation and warm, bare ground for basking.
Chequered Skipper Caterpillar (Carterocephalus palaemon)
Pale greenish-cream with a dark head and subtle lateral stripe, this caterpillar feeds inside a tube made from rolled purple moor-grass or other grasses, secured with silk. Extinct in England by 1976 but surviving in Scotland, it has since been successfully reintroduced in Northamptonshire.
Large Skipper Caterpillar (Ochlodes sylvanus)
Green with a darker dorsal stripe and a bluish-white waxy coating, this caterpillar feeds on cock’s-foot and other broad-leaved grasses. It constructs a characteristic shelter by drawing a grass blade into a tube and securing it with silk. It overwinters as a small larva and completes its growth in spring.
Small Skipper Caterpillar (Thymelicus sylvestris)
Bright green with a pale yellowish stripe along its side, this caterpillar feeds on Yorkshire fog and other grasses inside a rolled tube of leaf. It overwinters as an egg — uniquely for British skippers — and the caterpillar’s entire life is spent within a shelter that it carefully constructs and repairs.
Duke of Burgundy Caterpillar (Hamearis lucina)
Pale greyish-brown and somewhat woodlouse-like, this caterpillar feeds on the leaves of cowslip and primrose. It feeds openly on leaf surfaces, where its colouration provides reasonable camouflage against the pale green underside of leaves. It is Britain’s only member of the otherwise tropical Riodinidae family.
White-letter Hairstreak Caterpillar (Satyrium w-album)
Pale green and flattened, with a pattern of diagonal lines that mimics the texture of elm bark and flowers, this caterpillar feeds on the buds, flowers, and leaves of elm trees. The catastrophic loss of elms to Dutch elm disease has severely reduced its populations. It is barely visible against its host plant.
Black Hairstreak Caterpillar (Satyrium pruni)
This extraordinarily cryptic caterpillar is pale green or brownish, shaped to resemble a leaf bud or bark, and feeds on blackthorn. It is considered one of the hardest British caterpillars to find. The species is confined to a small area of the East Midlands, associated with ancient blackthorn woodland.
Brown Hairstreak Caterpillar (Thecla betulae)
Bright green and flattened with diagonal yellowish stripes, this caterpillar blends perfectly with the unfolding leaves of blackthorn. It is the largest of the British hairstreak caterpillars. The adult female lays her eggs singly at the base of blackthorn twigs, and the caterpillar emerges in April to feed on fresh new growth.
Purple Hairstreak Caterpillar (Favonius quercus)
Dark brown and flattened, camouflaged to resemble an oak bud, this caterpillar feeds on oak leaves and buds. It is associated with oak woodland canopy and lives a largely secretive life high in the treetops. The adult butterfly also rarely descends below the canopy, making both larva and adult rarely observed close-up.
Pearl-bordered Fritillary Caterpillar (Boloria euphrosyne)
Black and spiny, with rows of short bristly spines and orange-tipped tubercles, this caterpillar feeds on common dog violet. It hibernates over winter and completes its development in early spring, basking in the warm sun of open woodland rides to speed its growth. One of the first fritillaries to fly in spring.
Small Pearl-bordered Fritillary Caterpillar (Boloria selene)
Very similar to the Pearl-bordered Fritillary caterpillar, this dark, spiny larva also feeds on violets. It can be distinguished by subtle differences in tubercle patterning. It favours damp meadows, woodland edges, and moorland, and overwinters in leaf litter before resuming feeding when temperatures rise in spring.
High Brown Fritillary Caterpillar (Argynnis adippe)
Dark with rows of pale spines and reddish-based tubercles, this caterpillar feeds on violets in open, bracken-rich woodland. It is one of Britain’s most endangered butterfly species, and its caterpillar requires very specific warm, south-facing slopes with both violets and bracken for shelter and basking.
Dark Green Fritillary Caterpillar (Argynnis aglaja)
Velvety black with rows of short orange-based spines, this caterpillar feeds nocturnally on dog violet and hides during the day. It is found in open habitats from coastal dunes to upland grassland. Despite its wide distribution, it is a surprisingly rarely observed caterpillar due to its nocturnal habits and dark camouflage.
Heath Fritillary Caterpillar (Melitaea athalia)
Black and spiny, feeding gregariously on plantain, cow-wheat, and foxglove, this caterpillar basks communally in the sun on exposed vegetation. Its gregarious behaviour in early instars gives way to a solitary life in the final stages. It is one of the rarest British butterflies, with a highly restricted and fragmented distribution.
Wood White Caterpillar (Leptidea sinapis)
Slim, pale green, and almost completely smooth, this caterpillar feeds on bird’s-foot trefoil and meadow vetchling. Its slender form and uniform green colouration make it virtually impossible to detect among the fine stems and tendrils of its host plant. The adult is Britain’s most delicate-looking butterfly, with soft, rounded white wings.