23 Types of Caterpillars in Maryland and How to Identify Them
October 17, 2026
Walk through a Maryland backyard in late spring and you’re almost guaranteed to find a caterpillar munching on something, whether it’s a tomato plant, an oak leaf, or a patch of milkweed. The state’s mix of forests, farmland, and suburban gardens supports an unusually wide range of caterpillar species, some prized by gardeners and others considered serious pests. Knowing the different types of caterpillars found in Maryland helps homeowners decide which ones to protect and which ones need to go.
This rundown covers 23 caterpillars commonly reported across the state, from the iconic monarch to lesser-known species like the mimosa webworm. Each entry includes identifying features, host plants, and practical notes for anyone who spots one crawling across a leaf or a porch railing.
Pro Tip: Most caterpillars in Maryland are harmless to touch, but a handful have stinging spines. When in doubt, observe without handling until you’ve confirmed the species.
1. Monarch Caterpillar
The monarch caterpillar (Danaus plexippus) is one of the most recognizable insects in North America, with bold yellow, white, and black bands running the length of its body. According to Butterflies and Moths of North America, caterpillar hosts include milkweeds such as common milkweed, swamp milkweed, and showy milkweed, along with milkweed vine in tropical regions. These plants contain toxic compounds that the caterpillar stores in its body, which is why most milkweeds contain cardiac glycosides that are stored in the bodies of both the caterpillar and adult, making them distasteful and emetic to predators.
Monarch larvae feed exclusively on milkweed leaves, making the plant essential to their survival. Gardeners who want to support monarchs can plant native milkweed species, and the National Park Service notes that the monarch butterfly species has existed for an estimated one million years. Maryland sees monarchs most heavily during their fall migration south, when adults stop in gardens and meadows to feed before continuing their multi-generational journey.
2. Spicebush Swallowtail Caterpillar
The spicebush swallowtail caterpillar (Papilio troilus) is a master of disguise. Young caterpillars are mottled brown and white, closely resembling bird droppings on a leaf, while older instars turn bright green with two large orange-and-black eyespots on the swollen thorax that mimic a small snake’s head.
This species feeds almost exclusively on spicebush (Lindera benzoin) and sassafras, both common understory shrubs in Maryland’s hardwood forests. The caterpillar folds a leaf into a protective shelter during the day and emerges at night to feed, a behavior that makes it tricky to spot even on a heavily used host plant. Gardeners interested in native plantings often compare notes with growers in Virginia, where spicebush grows along similar forest edges.
3. Imported Cabbageworm
The imported cabbageworm (Pieris rapae) ranks among the most familiar garden pests in the state. Coloring is light green with small yellow dots along the sides, and the species is small, relatively thin, and appears velvety, making it easy to miss among cabbage and kale leaves until the damage is already visible.
Cabbageworms grow into cabbage white butterflies, which are one of the most abundant butterflies in Maryland, and if you see a white butterfly in the spring, chances are it’s a cabbage white. This caterpillar targets brassica-family crops almost exclusively, including broccoli, collards, and brussels sprouts, chewing irregular holes through leaves and sometimes boring into developing heads.
4. Milkweed Tussock Caterpillar
The milkweed tussock caterpillar (Euchaetes egle) shares its host plant with the monarch but looks nothing alike. Instead of smooth bands, this species is covered in dense tufts of black, white, and orange hair-like setae arranged in rows down its back.
Young milkweed tussock caterpillars feed in tight groups, often stripping entire milkweed leaves down to the veins before dispersing as they mature. Because they compete with monarchs for the same food source, gardeners managing milkweed patches for butterfly conservation sometimes have to decide how much tussock moth activity to tolerate. The caterpillar’s hairs can cause mild skin irritation in sensitive individuals, though it isn’t considered dangerous.
5. Eastern Tent Caterpillar
The eastern tent caterpillar (Malacosoma americanum) is impossible to miss once its silk tents appear in the forks of cherry and crabapple branches each spring. The Maryland Department of Agriculture describes fully grown caterpillars as about 2 inches long, black with solid white stripes down the middle of the back and a row of pale blue oval spots on each side.
According to the University of Maryland Extension, eastern tent caterpillars are native insects to Maryland and can be found all over the eastern United States and southern Canada. These caterpillars feed in groups and can grow as large as 2 inches, boldly patterned with black, orange, white, and blue colors. While the webbing looks alarming, healthy trees generally recover from a season of defoliation.
6. Cabbage Looper
The cabbage looper (Trichoplusia ni) moves with a distinctive arching motion because it lacks a full set of middle prolegs, forcing it to loop its body forward like an inchworm. The Baltimore-based Edible Eden Foodscapes notes that cabbage loopers are a small lime green caterpillar that turn into an unremarkable brown moth.
Important Note: Cabbage loopers and imported cabbageworms are frequently confused since both are small and green on brassica crops. Loopers move with a distinct arching gait, while cabbageworms crawl in a straight line using all their prolegs.
Cabbage loopers are named after their diet, eating cabbage but also anything else in the brassica family, including kale, broccoli, collard, and brussels sprouts. Gardeners don’t need to feel bad about removing them, since loopers tend to move in herds of hungry little caterpillars that can quickly skeletonize leaves.
7. Tomato Hornworm
Few garden pests inspire as much alarm as the tomato hornworm (Manduca quinquemaculata), a thick green caterpillar that can grow to several inches long. Edible Eden Foodscapes describes hornworms broadly, noting that hornworms are large, muscular, and green with alternating diagonal white stripes and false eyes, along with a curved horn-like projection at the rear end that gives the group its name.
Despite its size, the tomato hornworm is surprisingly well camouflaged against tomato foliage and often goes unnoticed until stems are stripped bare. It also feeds on pepper, eggplant, and potato plants, all members of the nightshade family. Adult hornworms become five-spotted hawk moths, large nocturnal fliers sometimes mistaken for hummingbirds at dusk.
8. Zebra Swallowtail Caterpillar
The zebra swallowtail caterpillar (Eurytides marcellus) is a smooth, plump green caterpillar marked with narrow black and yellow bands across its back, giving it a striped appearance unlike any other swallowtail in the region. Unlike its relatives, this species has a highly specific diet restricted almost entirely to pawpaw trees.
Because pawpaw thrives in the moist bottomland forests found throughout central and southern Maryland, zebra swallowtail populations tend to track wherever pawpaw groves grow undisturbed. Gardeners who plant pawpaw for its fruit sometimes get zebra swallowtail caterpillars as an unexpected bonus, since the tree supports no other common butterfly larvae in the area.
9. Black Swallowtail Caterpillar
The black swallowtail caterpillar (Papilio polyxenes) is a familiar sight in vegetable gardens, where it feeds on parsley, dill, fennel, and other members of the carrot family. Mature caterpillars are bright green with black bands studded with yellow dots running across each body segment.
This species is one of the easier caterpillars to raise at home since its host plants are common culinary herbs. Gardeners who want to attract black swallowtails often leave a few extra dill or parsley plants unharvested specifically for the caterpillars. Full details on butterfly species recorded across the state, including the black swallowtail, appear on the List of Butterflies of Maryland.
10. Palamedes Swallowtail Caterpillar
The Palamedes swallowtail caterpillar (Papilio palamedes) closely resembles the spicebush swallowtail, with a swollen green thorax and large false eyespots meant to startle predators. The two species are best separated by host plant and range rather than appearance alone.
Palamedes swallowtails feed primarily on redbay and sweetbay magnolia, trees concentrated in Maryland’s coastal wetlands and the lower Eastern Shore. This caterpillar is considerably less common statewide than its spicebush cousin, making sightings in Maryland’s coastal plain a treat for local butterfly watchers. Anyone comparing swallowtail populations across the mid-Atlantic might also check caterpillar activity in Tennessee, where overlapping host plants support similar species.
| Swallowtail Caterpillar | Primary Host Plant | Key Identifying Feature |
|---|---|---|
| Spicebush Swallowtail | Spicebush, sassafras | Green body with large orange-black eyespots |
| Zebra Swallowtail | Pawpaw | Narrow black and yellow stripes |
| Black Swallowtail | Dill, parsley, fennel | Black bands with yellow dots |
| Palamedes Swallowtail | Redbay, sweetbay magnolia | Nearly identical to spicebush, found in coastal wetlands |
11. Cecropia Moth Caterpillar
The cecropia moth caterpillar (Hyalophora cecropia) is the largest native caterpillar found in Maryland, reaching lengths of nearly 4 inches at maturity. Its blue-green body is studded with rows of colorful tubercles, red and orange near the head and blue further down the body, each tipped with small black spines.
This species feeds on a wide range of hardwood trees, including maple, cherry, and birch, and spins a tough, papery cocoon attached lengthwise along a twig for winter. Because cecropia moths are among the largest insects in North America, hobbyists interested in raising moths at home often start with this species, a practice covered in more detail in guides to keeping insects as pets.
12. Buck Moth Caterpillar
The buck moth caterpillar (Hemileuca maia) demands caution. This dark, spiny caterpillar feeds on oak trees in groups and carries urticating spines that deliver a painful sting similar to a nettle or bee sting if touched.
Important Note: Buck moth caterpillars should never be handled bare-handed. Their spines can cause localized swelling, burning pain, and occasionally an allergic reaction in sensitive individuals.
Buck moths are unusual among Maryland’s moths because the adults fly during the day in late fall, well after most other moth species have finished their yearly cycle. Readers researching which species pose a genuine risk often cross-reference poisonous caterpillars found across North America, since the buck moth is one of the few truly stinging species in the mid-Atlantic.
13. Spongy Moth Caterpillar
The spongy moth caterpillar (Lymantria dispar) is a hairy, dark caterpillar marked with paired blue and red spots running down its back. This species was formerly known by a different common name until the Entomological Society of America renamed it “spongy moth” in 2022, a reference to the sponge-like texture of its egg masses.
Spongy moth caterpillars are invasive and capable of defoliating large stretches of oak and hardwood forest during outbreak years, a problem Maryland foresters monitor closely each spring. Populations fluctuate significantly from year to year depending on natural predators and weather conditions, with some seasons producing dramatic, visible defoliation and others passing with little noticeable impact.
14. Cankerworm
Cankerworms, including both the spring cankerworm and fall cankerworm, are slender, inchworm-style loopers that emerge in large numbers on shade trees in early spring. Like true inchworms, cankerworms lack a full complement of middle prolegs and move with a characteristic looping gait.
Heavy cankerworm infestations can strip oak, elm, and maple trees of their leaves within a few weeks, though healthy trees typically push out a second flush of foliage by midsummer. Maryland’s hardwood defoliator monitoring programs track cankerworm populations alongside eastern tent caterpillars and spongy moths, since all three can appear in the same forest stands during a bad outbreak year.
15. Bagworm
The bagworm (Thyridopteryx ephemeraeformis) is easy to overlook because the caterpillar spends its entire larval life inside a spindle-shaped bag built from silk and bits of the host plant, dragging the structure along as it feeds. From a distance, the bags look like small pinecones dangling from branch tips.
Pro Tip: Hand-pick and destroy bagworm cases on arborvitae and junipers in late winter before eggs hatch in spring. Once the caterpillars disperse, chemical treatment becomes far less effective.
Bagworms favor evergreens such as arborvitae, juniper, and cedar, though they will also feed on many deciduous trees when evergreen hosts are scarce. A heavy bagworm infestation can kill an ornamental evergreen outright, since conifers don’t regenerate lost foliage the way broadleaf trees do.
16. Fall Webworm
The fall webworm (Hyphantria cunea) builds large, loose silken webs at the ends of branches in late summer and early fall, a habit that often leads to confusion with the spring-active eastern tent caterpillar. Fall webworm caterpillars are pale with tufts of long hair and feed communally inside their web for protection.
This species attacks a wide variety of hardwood trees, including walnut, birch, and wild cherry, expanding its web as the colony grows and consumes nearby foliage. Because fall webworm activity occurs late in the growing season, the damage rarely threatens tree health the way earlier-season defoliators can.
17. Red-Humped Caterpillar
The red-humped caterpillar (Schizura concinna) is named for the bright red-orange hump located just behind its head, paired with black spines running the length of a yellow-striped body. Young caterpillars feed in groups, often lined up along a leaf edge, before dispersing as they mature.
This species targets fruit trees and ornamental shade trees alike, including apple, cherry, and birch. Infestations tend to be localized to a single branch or two rather than spreading across an entire tree, making hand removal a practical control option for homeowners who spot the colorful colonies early.
18. Yellow-Necked Caterpillar
The yellow-necked caterpillar (Datana ministra) is black with narrow yellow or orange stripes and a bright yellow-orange band directly behind the head that gives the species its name. When disturbed, these caterpillars rear up both ends of their bodies in a defensive display meant to deter predators.
Yellow-necked caterpillars feed in groups on oak, birch, and various fruit trees during late summer, often stripping individual branches bare before moving on. Because they feed gregariously and late in the season, damage is usually cosmetic rather than a serious threat to overall tree health.
19. Mimosa Webworm
The mimosa webworm (Homadaula anisocentra) is a small gray-brown caterpillar with faint longitudinal stripes that ties leaves together with silk webbing as it feeds. Despite its small size, a heavy infestation can leave an entire mimosa or honeylocust tree looking scorched and brown by midsummer.
This species has become more common on honeylocust street trees as mimosa trees have declined in parts of the mid-Atlantic, a shift also tracked by urban foresters in states like Ohio. Repeated annual defoliation can weaken affected trees over time, even though a single season of mimosa webworm activity rarely causes lasting damage.
20. Green-Striped Mapleworm
The green-striped mapleworm (Dryocampa rubicunda) is the larval stage of the rosy maple moth, one of the most colorfully patterned moths in North America as an adult. The caterpillar itself is green with dark longitudinal stripes and small black spines, feeding almost exclusively on maple leaves.
Populations can build quickly in late summer, with large groups capable of defoliating entire maple branches in residential neighborhoods. Despite the dramatic feeding damage, mature maple trees generally tolerate green-striped mapleworm outbreaks without lasting harm.
21. Catalpa Worm
The catalpa worm (Ceratomia catalpae) is the larval stage of the catalpa sphinx moth and feeds exclusively on catalpa trees, often in large defoliating groups. The Maryland State Archives has documented catalpa sphinx caterpillars in locations such as Glen Burnie, noting their presence as part of the state’s broader caterpillar fauna.
Mature catalpa worms are typically black or dark green with yellow markings and a small curved horn near the rear, similar in general shape to a tomato hornworm but restricted entirely to catalpa foliage. In parts of the South, catalpa worms are harvested as prized fishing bait, a tradition less common in Maryland but still practiced by some anglers who maintain catalpa trees specifically for this purpose, similar to bait-gathering traditions reported in Texas.
22. Orange-Striped Oakworm
The orange-striped oakworm (Anisota senatoria) is black with bold orange or yellow stripes and two long, curved black spines projecting from just behind the head, giving it a distinctive silhouette among Maryland’s oak-feeding caterpillars. Young caterpillars feed in dense clusters, often on a single branch, before spreading out as they grow.
Outbreaks tend to appear in late summer, sometimes stripping entire oak branches of leaves within days when population numbers peak. Because the damage occurs so late in the growing season, affected oaks generally recover the following spring without lasting injury.
23. Inchworm
Inchworms describe a broad group of caterpillars in the family Geometridae, named for their distinctive looping gait that results from missing middle prolegs. Rather than crawling smoothly, an inchworm arches its body to bring its hind end forward before extending its front half again, appearing to measure the surface as it travels.
Maryland hosts dozens of inchworm species feeding on everything from oak and maple to garden shrubs, with coloration ranging from bright green to mottled brown depending on the species and its preferred camouflage. Because so many unrelated moth families produce inchworm-style larvae, accurate identification usually requires looking at the adult moth or consulting detailed guides such as the Caterpillar Identification database for Maryland.
Key Insight: The looping gait seen in inchworms, cankerworms, and cabbage loopers all stems from the same evolutionary trait: a reduced number of prolegs compared to caterpillars with a full set of six pairs.
Maryland’s caterpillar diversity reflects the state’s varied landscape, from coastal wetlands supporting Palamedes swallowtails to suburban gardens hosting cabbage loopers and tomato hornworms. Gardeners and homeowners benefit from learning to tell beneficial or harmless species, like the monarch and black swallowtail, apart from genuine pests such as the spongy moth or bagworm.
For readers curious about how Maryland’s caterpillar fauna compares elsewhere, similar identification guides exist for neighboring and distant states, including Connecticut, Wisconsin, and Iowa, along with broader overviews of how many caterpillar species exist worldwide. Those interested in the state’s wider insect and wildlife population may also want to look into Maryland’s beetles and Maryland’s snakes, both of which share habitat with many of the caterpillars described above.