How Many Legs Does a Caterpillar Have? True Legs vs. Prolegs

A caterpillar has six true legs, the same three pairs every insect carries, tucked up at the front just behind the head. The plump, fleshy stubs running down the rest of the body are not legs at all. They are prolegs, and only the six true legs carry through to the adult butterfly. Everything else falls away in the transformation.

Here is the short version:

• True legs: six total, three pairs on the thorax (the front section), jointed and hard, the same legs found on every insect.
• Prolegs: soft, fleshy false legs on the abdomen, tipped with rows of tiny hooks that grip the plant.
• What lasts: only the six true legs make it to adulthood. The prolegs are a caterpillar-only feature.

The caterpillar in these photos is an eastern black swallowtail, one of a crew Mandi (@mrsmandivaughn) raised on dill in our backyard container garden this year. She caught the leg detail up close on video, and you can watch the prolegs grip the dill to see exactly what we mean. The front "hands" everyone points at are the only legs this caterpillar will ever keep.

How many legs does a caterpillar have?

Every insect, caterpillars included, has six true legs arranged as three pairs on the thorax, the segment right behind the head. On a caterpillar those are the small, pointed, jointed legs clustered up front. They are hard-shelled like the legs of a beetle or a bee, because they are built on the exact same body plan.

Those front legs do real work. The caterpillar uses them to hold onto a leaf edge and guide food to its mouth while it feeds. That is worth remembering, because the caterpillar is the only life stage that eats solid food. The adult butterfly only sips nectar through a coiled tongue, so all of the eating and growing has to happen now, in this stage, on the host plant.

What are prolegs?

The chubby legs running down the middle and back of the body are prolegs, and they are a completely different structure. Prolegs are not jointed like true legs. They are soft, fleshy extensions of the body wall, more like little stumps that inflate and grip as the caterpillar moves.

Look closely at the bottom of each proleg and you will see rows of tiny hooks called crochets. They work almost like microscopic grappling hooks, catching into the surface of a leaf or stem so the caterpillar can hang on tight, even upside down. Most caterpillars carry up to five pairs of prolegs, including a pair at the very tail end that acts like a set of rear clampers. That combination of front true legs pulling and prolegs gripping is what gives a caterpillar its smooth, rolling, wave-like walk.

Why only the true legs make it to adulthood

Here is where it gets interesting. Prolegs are a larval feature, built for one job: holding onto the host plant while the caterpillar eats and grows. The adult butterfly does not need them. It walks, perches, and clings with its six true legs and feeds on nectar instead of leaves.

So when the caterpillar finishes growing, forms its chrysalis, and later emerges as a butterfly, the body is completely rebuilt. The six true legs stay. Every proleg is gone. (Butterflies emerge from a chrysalis, by the way. They do not hatch. Hatching is for eggs.) The next time you see a caterpillar waving those front legs around, you are looking at the only legs it will ever keep.

Those true legs matter later on, too. A female black swallowtail actually tastes plants with her feet, drumming her front legs on a leaf to read its chemistry before she lays an egg on it. The legs a caterpillar keeps are the same ones the adult uses to find the next dill plant to raise a family on.

Meet the caterpillar behind the "hands"

Black swallowtails are picky about where they grow up. Females lay eggs only on plants in the carrot and parsley family (Apiaceae): dill, fennel, parsley, cilantro, and carrot tops. Those plants are loaded with natural compounds that deter most insects, and black swallowtail caterpillars are one of the few that evolved to detox them and eat freely.

That is why we grow dill on purpose a few feet from the back door and let it bolt. It becomes a host buffet for the caterpillars. Our whole backyard container garden is grown with no sprays of any kind, which is what lets butterflies, bees, spiders, and beneficial predators do their thing without us interfering. If you want to see the full journey from egg to emergence, we walk through all of it in our guide to raising black swallowtail butterflies in a container garden.

If you want caterpillars like this in your own space, the move is simple: plant their host plants. A single container of dill or fennel is enough to invite a female to lay, and a few zinnias nearby give the emerged adults something to nectar on. You can grow the host plants right from seed, and they do great in fabric grow bags or containers if you are short on ground space. We started ours indoors in plug trays before moving them out. For the bigger picture on planting for pollinators in our area, our post on pollinator-friendly gardens for North Texas covers what to plant and why.

What it turns into

After a couple of weeks of eating, the caterpillar empties its gut, wanders off the plant, and forms its chrysalis. Somewhere between about nine and eighteen days later in summer, an adult black swallowtail emerges, wings soft and crumpled at first, then pumped full and hardened over a few hours before its first flight. Six legs. No prolegs. Ready to nectar and start the cycle over.

Watching that whole transformation play out on a plant you grew yourself is one of the best parts of keeping a garden built for bugs. It also fits neatly with the same grow-your-own mindset behind growing your own food indoors and using the empty pots you already have.

Frequently Asked Questions

How many legs does a caterpillar have?

A caterpillar has six true legs, arranged as three pairs on the thorax right behind the head, plus several pairs of fleshy prolegs on the abdomen. The six true legs are the same three pairs every insect has. Only those six carry over to the adult butterfly.

What is the difference between true legs and prolegs?

True legs are hard, jointed, and located on the thorax, and they are permanent parts of the insect. Prolegs are soft, fleshy, unjointed stubs on the abdomen tipped with tiny hooks, and they exist only during the caterpillar stage to grip the host plant.

Do butterflies have prolegs?

No. Prolegs are a caterpillar-only feature. When the caterpillar transforms inside its chrysalis and emerges as a butterfly, the prolegs are gone and only the six true legs remain.

What do the hooks on caterpillar prolegs do?

Those hooks are called crochets. They are arranged in rows on the bottom of each proleg and catch into leaf and stem surfaces like miniature grappling hooks, letting the caterpillar hold on tight even while feeding upside down.

Do all caterpillars have the same number of prolegs?

Not exactly. Most butterfly and moth caterpillars carry up to five pairs of prolegs, including a rear pair at the tail, but the count can vary by species. The six true legs, however, are consistent across insects.

Final Thoughts

The "cute little hands" that make caterpillar videos go viral are the real story here. They are the only legs the insect keeps for life, while the grippy prolegs that do all the heavy holding are temporary tools for one stage. Once you know what you are looking at, you will notice it every time.

These little details are exactly what we love watching for out in the garden. You can follow along with more macro bug photography and pollinator finds on Mandi's page, @mrsmandivaughn. For more backyard bug stories, our takes on the great North Texas pill bug invasion and the year's top gardening trends are a good next read.

Related Blogs

• How to Raise Black Swallowtail Butterflies in a Container Garden
• The Black Swallowtail Caterpillar's Osmeterium: That Orange Forked Defense Organ
• Pollinator-Friendly Gardens in Hunt County: Native Plants & Herbs for North Texas
• Fabric Grow Bags: Why We Use Them for Our Backyard Garden
• Holy Poly They're Taking Over! The Great Pill Bug Invasion of North Texas
• Worried About Brood XIX and XIII Cicadas Eating Your Garden? Grow Microgreens Indoors Instead
• Have a Few Empty Planting Pots Laying Around? Grow Microgreens in Them!
• How to Grow Your Own Food Indoors: The Best Way to Learn Microgreens
• Top 5 Gardening Trends to Watch in 2025: What's Growing This Year?

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Happy growing!