Invertebrate Identifier: Name Creepy-Crawlies by Photo

What to look at when identifying an invertebrate

A collage contrasts a spider’s and beetle’s body regions, a millipede’s repeated rings, and the soft bodies of a slug and snail.

Body segmentation

Start by looking for repeated body sections. A spider has two main body regions, insects have a head, thorax and abdomen, and centipedes and millipedes repeat similar trunk segments. Clear segments help separate a many-legged arthropod from a slug, snail or smooth-bodied larva.

Multiple panels compare the legs of a centipede, grasshopper, spider, millipede, and caterpillar with a legless slug and earthworm.

Legs, many legs or none

Leg count is one of the quickest filters, as long as you can see the legs. Adult insects have six, adult arachnids usually eight, centipedes and millipedes many, and slugs, snails and worms none. Check where the legs attach and whether they run the length of the body.

Four close views show a snail’s spiral shell, a beetle’s hard wing covers, a slug’s mantle, and a caterpillar’s soft segmented body.

Shells, plates and soft coverings

A shell, plates or a hard outer surface changes the shortlist right away. Snails carry an external shell, slugs usually don't, beetles have hard wing covers, and many crustaceans look armored. Soft skin still has useful features, like a slug's mantle or a caterpillar's fleshy prolegs.

Three habitat panels show a caterpillar on a leaf, a snail and small crustacean among pond plants, and shore animals on wet rocks.

Land, freshwater or sea

The same shape means different things on a leaf, in pond water or on a beach rock. Freshwater finds are often insect larvae, snails and small crustaceans. Sea creatures may show tube feet, arms arranged like a star, or shells you'll never meet in the garden.

Compare real field-guide examples: Octopus · Horseshoe Crab · Blue Crab

Common invertebrate mix-ups

Insect versus arachnid: Don't use “insect” as a catch-all. Spiders, harvestmen, mites, ticks and scorpions are arachnids. Adult insects have six legs and usually a distinct thorax and abdomen. Adult arachnids usually have eight legs and no antennae, though young ticks and mites can have six. A clear front or side view often settles it fast.
Centipede versus millipede: Centipedes have one pair of legs per trunk segment, a flatter body and legs held out to the sides. Millipedes have two pairs on most segments and a rounder, slower-looking body. Count carefully from a sharp photo, since overlap and angle can hide legs.
Slug or snail versus worm: Slugs and snails glide on a broad muscular foot and often show tentacles or a saddle-like mantle near the front. Worms have no foot. Earthworms show repeated rings, while many fly larvae are smooth, tapered and clearly not mollusks. A shell makes a snail easy, but shell-less slugs are common.

When it looks like a worm or larva

Three close views compare a ringed earthworm in soil, a caterpillar with small legs on a leaf, and a pale legless larva on damp organic matter.

A long, soft body doesn't automatically mean worm. Many insect larvae are legless or have tiny legs near the head, and some fly larvae look like smooth, tapered tubes. Earthworms show repeated rings along the body, while caterpillars usually have a distinct head and a few fleshy prolegs.

Look closely at both ends. A hardened head capsule, obvious mouthparts or several small legs point to a larva. An evenly ringed body, especially in damp soil or compost, fits an earthworm better. In water, a wormlike animal may be a midge larva, a leech (an earthworm relative) or a flatworm.

Clues from gardens, ponds and shorelines

A habitat collage shows a spider, slug, and beetle on land; aquatic insects, a snail, and shrimp in water; and shellfish and crabs on shore rocks.

Tiny garden invertebrates make more sense once you notice where they were and how they move. A springy jumper on soil, a slow glider on leaves and a fast runner under a flowerpot are built differently, even at similar sizes. Region and season help when you compare with a local guide.

Water changes the shortlist. Pond photos often show insect nymphs and larvae, snails, water boatmen, scuds and other small crustaceans, or flatworms. Shoreline and sea finds may have shells, pincers or lots of small swimming legs. If you have several photos, compare them yourself and upload the clearest view.

Photo tips for small creatures

Show the whole body shape
Fill the frame with the animal, but keep enough in view to show its overall shape. For many-legged creatures, a side view often shows body height and leg placement better than a straight top view.
Focus on the front half
If the creature is tiny, tap to focus on the head or front half. Antennae, eyes, mouthparts or a slug's mantle are more useful than a distant full scene.
Keep some habitat in view
Include the surface or setting when it helps: leaf, soil, pond water, rock pool or web. That context can separate freshwater, land and sea candidates from one image.

Invertebrate identification FAQ

I found a bug with lots of legs. What is it?

It's most likely a centipede or a millipede, and the leg pairs tell them apart. Centipedes have one pair of legs per body segment and often look flatter. Millipedes have two pairs on most segments and a rounder body, though not every segment is easy to read in a photo.

What's the difference between a slug and a snail?

A slug is basically a snail without an obvious shell. Both are mollusks, not worms. Most slugs have no external shell, though some keep a small internal one. Look for a broad gliding foot, tentacles on the head and a saddle-like mantle just behind it.

How do I identify a creature from a pond or ditch?

Start with the broad group: a clear photo can often separate snails, insect larvae, crustaceans, flatworms and leeches. Try to capture the whole body, including tails, gills, legs or shell. Whether it came from fresh or salt water also helps when you compare it with a regional guide.

What details matter for a tiny creature in the garden?

Body shape matters more than size, since lots of unrelated invertebrates are tiny. Look at the outline, legs, antennae, wings or no wings, and whether the body looks soft, armored or segmented. Upload your clearest close-up rather than a wide garden scene.

How can I tell a worm from an insect larva?

Check the head end. A distinct head, mouthparts or small legs near the front point to an insect larva. Earthworms have repeated ring-like segments and no legs. Some fly larvae are smooth and legless, so a sharp view of the head end helps most.

Is there an app for identifying bugs and creepy-crawlies with kids?

Yes. Snappit – Identify Anything for iPhone and Android identifies insects, spiders, snails and other wildlife from a photo, with short facts kids can follow. When a photo isn't clear enough for a species, it may still name the broad group, like slug or millipede. Each find becomes a collectible card with a rarity tier in a private family collection. No ads or chat; free to download with free daily IDs and an optional subscription for unlimited snaps.

Is a spider an insect?

No, spiders are arachnids. Adult insects have six legs and antennae; spiders have eight legs and no antennae. If your photo clearly shows the front of the body and the legs, that difference is usually easier to see than color or pattern.

Can an empty shell, shed skin or case be identified?

Sometimes. A snail shell, a shed exoskeleton or a portable case built by a larva can narrow the group a lot, especially when the shape and surface texture are clear. A species-level match is harder without the animal, so photograph the object close up and from the side.

Invertebrate identifier.What creature is this?

What did you find?

Upload a clear photo

Check the match

Collect and keep exploring

Meet the creepy-crawlies

How to identify an invertebrate from a photo

What to look at when identifying an invertebrate

Body segmentation

Legs, many legs or none

Shells, plates and soft coverings

Land, freshwater or sea

Common invertebrate mix-ups

When it looks like a worm or larva

Clues from gardens, ponds and shorelines

Photo tips for small creatures

Show the whole body shape

Focus on the front half

Keep some habitat in view

Invertebrate identification FAQ

Further reading

A discovery is just the beginning

Keep your discoveries together

Facts for curious families

Find a reason to look again

Take your curiosity somewhere new

Maria Mitchell Aquarium

Heal the Bay Aquarium

Cabrillo Marine Aquarium