Field Entomological Key • Filter by texture, markings and host

Visual Caterpillar & Chrysalis Identifier

Found a mystery caterpillar in your garden or schoolyard? Select its physical texture, color patterns, or host plant below to instantly match species, verify safety, and access rearing protocols.

Uncertain What You Found on the Trail?New Diagnostic Key

Answer 3 visual questions (Life Stage, Physical Traits, Host Plant) to identify wild eggs, larvae, cocoons, and butterflies with instant sting/toxicity flags, look-alike comparisons, and ethical husbandry guidelines.

1Physical Texture & Form

2Dominant Colors & Patterns

3Host Plant Discovered On

Matches Found: 16 species

PLATE V • FIG. 1 — LARVAL MORPHOLOGYMonarch Caterpillar (5th Instar)

Host:Asclepias Milkweed ONLY

Illustration, not to scale

Smooth skin, no spines

Monarch Caterpillar

Adult: Monarch Butterfly (Danaus plexippus)

Field Diagnostic Clues:

•Found EXCLUSIVELY on Asclepias Milkweed species
•2 pairs of black filaments (front pair is longer)

Host Plants:

Common MilkweedSwamp MilkweedButterfly Weed

PLATE V • FIG. 2 — LARVAL MORPHOLOGYBlack Swallowtail Caterpillar

Host:Apiaceae (Dill, Fennel, Parsley, Carrots)

Illustration, not to scale

Extrudes an osmeterium when handled

Parsley Worm / Black Swallowtail Caterpillar

Adult: Eastern Black Swallowtail (Papilio polyxenes)

Field Diagnostic Clues:

•Found eating garden culinary herbs (Dill, Fennel, Parsley) or native Golden Alexanders
•Orange osmeterium scent organ protrudes if touched gently behind head

Host Plants:

DillFennelParsley

PLATE V • FIG. 3 — LARVAL MORPHOLOGYEastern Tiger Swallowtail Caterpillar

Host:Tulip Poplar, Cherry, Sweetbay Magnolia

Illustration, not to scale

Extrudes an osmeterium when handled

Tiger Swallowtail Caterpillar

Adult: Eastern Tiger Swallowtail (Papilio glaucus)

Field Diagnostic Clues:

•Found on tree foliage (Cherry, Magnolia, Tulip Poplar)
•Two prominent yellow false eyes with blue pupils on enlarged thorax

Host Plants:

Tulip PoplarBlack CherrySweetbay Magnolia

PLATE V • FIG. 4 — LARVAL MORPHOLOGYGulf Fritillary Spiny Larva

Host:Passionflower Vines (Passiflora incarnata)

Illustration, not to scale

Soft branching spines, not urticating

Passionvine Spiny Caterpillar

Adult: Gulf Fritillary (Agraulis vanillae)

Field Diagnostic Clues:

•Found feeding vigorously on Passionflower (Passiflora) vines in southern and coastal regions
•Bright orange body with intimidating (yet soft) branching black spines

Host Plants:

Purple Passionflower / MaypopCorkystem PassionflowerYellow Passionflower

PLATE V • FIG. 5 — LARVAL MORPHOLOGYPipevine Swallowtail Caterpillar

Host:Dutchman’s Pipe & Snakeroot (Aristolochia)

Illustration, not to scale

Soft tubercles; sequesters aristolochic acids

Pipevine Caterpillar / Red-Horned Velvet Caterpillar

Adult: Pipevine Swallowtail (Battus philenor)

Field Diagnostic Clues:

•Found on native Aristolochia (Dutchman’s Pipe or Snakeroot)
•Velvety dark body with glowing orange/red fleshy horns

Host Plants:

Dutchman’s PipeVirginia SnakerootWoolly Dutchman’s Pipe

PLATE V • FIG. 6 — LARVAL MORPHOLOGYGiant Swallowtail ("Orange Dog")

Host:Citrus, Common Rue, Prickly Ash

Illustration, not to scale

Extrudes an osmeterium when handled

Orange Dog / Bird Dropping Caterpillar

Adult: Giant Swallowtail (Papilio cresphontes)

Field Diagnostic Clues:

•Looks convincingly like a fresh, glossy bird dropping on Citrus, Rue, or Prickly Ash foliage
•Erects bright red forked horns from behind head when touched

Host Plants:

Common RuePrickly AshWafer Ash / Hoptree

Soft branching spines, not urticating

Vertical J-Hang

Thistle Caterpillar

Adult: Painted Lady (Vanessa cardui)

Field Diagnostic Clues:

•Found inside silk webbed shelters on Thistles, Hollyhocks, or Sunflowers
•Spiky body with yellowish-white flecks and side stripes

Host Plants:

ThistlesMallows & HollyhocksStinging Nettle

Soft branching spines, not urticating

Vertical J-Hang

Nettle Caterpillar

Adult: Red Admiral (Vanessa atalanta)

Field Diagnostic Clues:

•Found exclusively in folded single-leaf tents on Nettle plants (Urtica or stingless False Nettle)
•Spiky body with white flecks along the side

Host Plants:

Stinging NettleWood NettleFalse Nettle

PLATE V • FIG. 9 — LARVAL MORPHOLOGYLuna Moth Caterpillar

Host:Sweetgum, Birch, Hickory, Walnut

Illustration, not to scale

Blunt knobbed tubercles, not urticating

Giant Luna Silkworm

Adult: Luna Moth (Actias luna)

Field Diagnostic Clues:

•Found on Sweetgum, Birch, or Walnut tree leaves
•Huge plump lime-green body with tiny pink dots

Host Plants:

SweetgumBirchHickory

PLATE V • FIG. 10 — LARVAL MORPHOLOGYMourning Cloak ("Spiny Elm Caterpillar")

Host:Willow, Elm, Poplar, Birch

Illustration, not to scale

Soft branching spines, not urticating

Spiny Elm Caterpillar

Adult: Mourning Cloak (Nymphalis antiopa)

Field Diagnostic Clues:

•Found feeding in large groups on Willow or Elm trees in early summer
•Black spiky body with a line of glowing red dots down the spine

Host Plants:

WillowAmerican ElmCottonwood / Poplar

Soft branching spines, not urticating

Vertical J-Hang

Buckeye Caterpillar

Adult: Common Buckeye (Junonia coenia)

Field Diagnostic Clues:

•Found eating common lawn Plantain weeds or garden Snapdragons
•Dark body with iridescent blue spines on bright orange bases

Host Plants:

PlantainSnapdragonsWild Petunia

Smooth skin, no spines

Silk Girdle / Twig Sling (45°)

Senna Caterpillar / Sulphur Larva

Adult: Cloudless Sulphur (Phoebis sennae)

Field Diagnostic Clues:

•Found on Wild Senna or Partridge Pea foliage
•Changes color to match yellow flowers or green leaves

Host Plants:

Wild SennaPartridge PeaSicklepod

Extrudes an osmeterium when handled

Silk Girdle / Twig Sling (45°)

Zebra Swallowtail Caterpillar

Adult: Zebra Swallowtail (Protographium marcellus)

Field Diagnostic Clues:

•Found EXCLUSIVELY on Pawpaw foliage (Asimina spp.)
•Smooth pea-green body with a crisp yellow and black collar stripe

Host Plants:

PawpawSmallflower PawpawDwarf Pawpaw

Extrudes an osmeterium when handled

Silk Girdle / Twig Sling (45°)

Spicebush Caterpillar / Snake Mimic

Adult: Spicebush Swallowtail (Papilio troilus)

Field Diagnostic Clues:

•Found tucked inside folded leaf tents on Spicebush or Sassafras
•Massive cartoon snake false eyes with luminous blue pupils

Host Plants:

Northern SpicebushSassafrasSweetbay Magnolia

Blunt knobbed tubercles, not urticating

Vertical J-Hang

Viceroy Caterpillar

Adult: Viceroy Butterfly (Limenitis archippus)

Field Diagnostic Clues:

•Found feeding on Willow or Cottonwood/Aspen leaves
•Two clubbed bristly horns on the upper thorax

Host Plants:

Black WillowSandbar WillowEastern Cottonwood

Blunt knobbed tubercles, not urticating

Ground Leaf Litter Cocoon

Giant Cecropia Caterpillar

Adult: Cecropia Silkmoth (Hyalophora cecropia)

Field Diagnostic Clues:

•Giant 4-inch sea-green caterpillar on Maple, Cherry, or Willow
•Bright coral-red tubercles on front segments

Host Plants:

Black CherrySilver MapleSugar Maple

Taxonomic & Field Husbandry Manuals

Related Master Guides & Larval Pathology

Diagnostic Keys

Larval Stages & J-Hang

Monarch Instars & Ecdysis Timeline →

Millimeter growth rates, head capsule slips, silk pad button spinning, and pre-pupal drop mechanics.

15 min read • Field Guide

Ecdysis Diagnostic

Molting vs. Dead Diagnostic →

24–36h motionless ecdysis markers, faceplate head capsule sheds, silk mats, and black death NPV triage.

12 min read • Diagnostic Matrix

Saturniidae Silk Moths

Luna & Giant Silk Moth Husbandry →

Deciduous branch sleeving, host tree switching rules, and 90-day winter cocoon cold-hours.

13 min read • Host & Cold Calculator

Egg Hunting & Loupe

Egg Finding & 20x Loupe Key →

Spotting female oviposition, distinguishing true vertical ribs from sap drops, and Petri dish incubation.

12 min read • 20x Loupe Simulator

Parasitoid Diagnostic

Tachinid & Wasp Diagnostic →

Identifying black ovipositor scars, silk hanging threads, and parasitoid pupation emergence.

16 min read • Diagnostic Key

Biosecurity Protocol

Host Plant Bleach Sanitization →

Neutralizing OE spores and NPV virus on wild foraged cuttings before feeding sensitive early instars.

12 min read • Field Guide

Diapause Manual

Chrysalis Overwintering Manual →

Managing overwintering silk cocoons and chrysalises: chilling units, humidity, and spring emergence.

15 min read • Master Guide

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