Head to head
Tadpole vs Caterpillar
A tadpole and a caterpillar are both juveniles that look nothing like the adult they will become, and both go through a dramatic transformation. But one is a vertebrate rebuilding its body in a pond, and the other is an insect that will effectively be taken apart and reassembled inside a case.
| Tadpole | Caterpillar | |
|---|---|---|
| Becomes a | Frog or toad | Moth or butterfly |
| Animal group | Vertebrate (amphibian) | Invertebrate (insect) |
| Lives in | Water | On land, on its food plant |
| Breathes with | Gills, then lungs and skin | Holes down the sides (spiracles) |
| Legs | None at first, grows four | Three pairs of true legs plus prolegs |
| Transformation | Gradual remodelling in the open | Rebuilt inside a pupa |
| Tail | Has one, resorbs it | No tail |
| Diet | Mostly algae; some are carnivorous | Leaves, in almost all species |
Tadpole vs Caterpillar: common questions
Do both a tadpole and a caterpillar undergo metamorphosis?
Yes, but of different kinds. A caterpillar undergoes complete metamorphosis, with a distinct pupal stage during which the larval body is largely dismantled and an entirely new adult body is built, so the larva and adult can look and live completely differently. A tadpole also undergoes a true metamorphosis, but it is more gradual and there is no pupa; the animal stays active and mobile throughout while its body is progressively rebuilt over days to weeks. Both processes are triggered by hormones and both convert an eating, growing juvenile into a mobile, reproducing adult.
Which one is further from its adult form?
The caterpillar, by most measures. A caterpillar has no wings, no compound eyes in the adult sense, no reproductive organs, a completely different mouth, a different gut, and a different way of moving, and inside the pupa its tissues are broken down so thoroughly that only small clusters of cells carry through to build the adult. A tadpole is closer, since it keeps the same spine, skull framework, and major organs and mostly adds legs and lungs while subtracting the tail and gills. So a frog is a heavily modified tadpole, whereas a butterfly is closer to a new animal grown from the spare parts of a caterpillar.
Are tadpoles and caterpillars important as food?
Very. Tadpoles can reach enormous densities in ponds and streams, where they graze algae and in turn feed fish, wading birds, snakes, turtles, diving beetles, and dragonfly larvae, transferring energy from plants up the food web. Caterpillars are the single most important food for most nesting songbirds, which time their breeding to the spring flush of caterpillars, and they also feed wasps, beetles, spiders, and small mammals. Because both are soft, abundant, and packed with protein and fat, whole communities of predators depend on the larval stage rather than the adult.