Parts of a Butterfly

In this guide

1. What are the parts of a butterfly?
2. Butterfly diagram: a labelled walk-through
3. The head: antennae, eyes, proboscis and palps
4. The thorax: the engine room
5. Legs: how many a butterfly has and what they do
6. The wings: veins, cells and scales
7. The abdomen: breathing, digestion and reproduction
8. Did you know?
9. Frequently asked questions

What are the parts of a butterfly?

Like every insect, an adult butterfly is built from three body regions: a head at the front, a thorax in the middle and an abdomen at the back. The head is the sensory and feeding centre, the thorax is the locomotion centre that carries the six legs and four wings, and the abdomen is the container for digestion, breathing, circulation and reproduction.

The outside of the body is an exoskeleton of chitin, hardened into plates and joined by flexible membranes; a butterfly has no bones, and its wings, legs and antennae are hollow, jointed extensions of the same shell. The framework is assembled during the pupal stage of the butterfly life cycle, when the leaf-chewing caterpillar is reorganised into an animal that drinks, flies and mates.

The diagram above labels the parts visible to the naked eye; a hand lens reveals the leg segments, the wing veins, the scales behind every colour and the breathing holes along the abdomen. The sections below take each region in turn and explain what every structure does and how it differs between the six butterfly families.

Butterfly diagram: a labelled walk-through

Reading the diagram from front to back:

• Antenna: one of the pair of slender sensory stalks on the head, ending in a swollen club. Butterflies have clubbed antennae; most moths do not.
• Compound eye: the large rounded eye on each side of the head, built from thousands of tiny lenses that give an almost all-round view.
• Proboscis: the drinking tube beneath the head, coiled like a watch spring until it uncoils to reach nectar.
• Head: the small front region carrying the antennae, eyes, proboscis and a pair of furry palps.
• Thorax: the thick, muscular middle region to which all six legs and all four wings attach.
• Legs: three pairs of jointed legs, one pair per thoracic segment; in the brush-footed family the front pair is tiny and tucked against the body.
• Forewing: the larger, more triangular front wing, attached to the middle segment of the thorax.
• Hindwing: the rounder rear wing, attached to the third thoracic segment and overlapped by the forewing.
• Abdomen: the soft, ringed rear region of ten segments, with breathing holes along its sides and the reproductive organs at its tip.

The same layout applies to a monarch, a tiny blue or a huge birdwing; only the proportions change.

The head: antennae, eyes, proboscis and palps

The head is a small, hard capsule carrying every major sense organ and the mouthparts.

Antennae

The two antennae are the butterfly's nose and part of its balance system. Each is a chain of small segments ending in a club, and its surface is packed with chemoreceptors that pick up floral scent, the pheromones of a mate and the odour of a host plant. At the base of each antenna, a cluster of sense cells called Johnston's organ registers how the antenna bends in the airflow, helping the insect judge its speed and orientation. The antennae also house part of the clock behind the sun compass of migrating monarchs, which lose their bearings when the antennae are painted over.

Compound eyes

Each compound eye is a dome of thousands of visual units called ommatidia, each with its own lens; depending on the species there are several thousand to about seventeen thousand per eye. The image they build is a coarse mosaic rather than a sharp picture, but it covers almost a full circle and is extremely sensitive to movement. Butterflies also see ultraviolet light, which reveals nectar guides on flowers and wing patterns invisible to us; a male cabbage white looks plain to our eyes but strikingly different from the female in UV.

Proboscis

The proboscis is the drinking straw: two half-tubes, the galeae, zipped together into a single channel and held coiled under the head by their own elasticity. Blood pressure and small muscles extend it when the butterfly lands on a flower, and a pump in the head draws nectar, sap, fruit juice or mineral-rich water up the tube. Its length is matched to the flowers a species visits, and the guide to what butterflies eat explains why an insect with this mouthpart cannot chew or bite.

Labial palps

Two furry, forward-pointing palps flank the base of the proboscis. Their sensory hairs sample the air and shield the coiled proboscis, and in a few families they are long enough to look like a snout.

The thorax: the engine room

The thorax is the box between head and abdomen, built from three fused segments, the prothorax, mesothorax and metathorax, each carrying one pair of legs. The second and third segments also carry the forewings and hindwings, so all four wings and all six legs are anchored to this one region.

Inside, the thorax is almost entirely muscle. Two sets of large flight muscles deform the thorax itself rather than pulling on the wings: one set flattens the box and lifts the wings, the other arches it and drives them down, while small steering muscles at the wing bases tilt each wing through the stroke. These muscles only work well when warm, which is why a butterfly basks before it flies. Outside, the thorax carries the first pairs of breathing holes, or spiracles, and a dense coat of hair-like scales that traps warmth and hides the segment boundaries, so the thorax of an eastern tiger swallowtail or a fritillary simply looks like a furry hump.

Legs: how many a butterfly has and what they do

A butterfly has six legs, arranged as a front, middle and hind pair on the three thoracic segments. Each leg has the standard insect sequence of segments from the body outwards: coxa, trochanter, femur, tibia, tarsus and, at the very end, the pretarsus with its pair of claws. The tarsus has five small joints, and the tibia often carries spurs and an antenna-cleaning comb.

Walking and gripping are the obvious jobs, but tasting is the surprising one. The feet carry chemoreceptors that read the chemistry of any surface the butterfly stands on, so a female drumming her forelegs on a leaf is checking that it is the right host plant before she lays.

The best-known exception concerns the largest family. In the brush-footed butterflies, which include the monarch, the admirals, the fritillaries and the common buckeye, the front pair of legs is shrunk to small brush-like stumps held against the thorax. These butterflies stand and walk on four legs, so a red admiral resting on a wall looks four-legged even to a careful observer; the reduced forelegs remain tasting organs but never touch the ground. Swallowtails, whites, blues and skippers use all six legs normally.

The wings: veins, cells and scales

A butterfly has four wings: a forewing and a hindwing on each side, both attached to the thorax. Each wing is a double sheet of transparent membrane stretched over a framework of hollow veins that carry blood, air tubes and nerves out to the tip.

Veins and cells

The vein pattern is fixed within a species and is the basis of scientific wing descriptions. From the leading edge backwards, the main veins are the costa, subcosta, radius, media, cubitus and anal veins, and the areas of membrane between them are called cells. The most important is the discal cell, a large closed cell in the centre of each wing; a dark spot "at the end of the cell" in a species profile means the far end of the discal cell.

Scales

Every colour on a wing comes from scales: tens of thousands of flattened plates, each about a tenth of a millimetre long, overlapping like roof tiles and rubbing off as coloured dust when handled. Some contain pigments (blacks, browns, yellows, reds); others carry microscopic ridges that scatter light to produce the metallic blue of a blue morpho and most greens. Scent scales, called androconia, occur only in males and release pheromones during courtship; they sit on the forewing in many whites and blues but on the hindwing in the monarch, whose black pouch is the best-known example, a detail the older version of this page oversimplified. Where scales are missing altogether, as over most of the wing of the glasswing butterfly, the membrane is transparent. More in the guide to butterfly colours.

Forewing and hindwing

The forewing is larger and produces most of the lift and thrust. The hindwing overlaps it at the base, so the pair beats as one surface; butterflies lack the bristle-and-hook coupling of moths. Butterflies whose hindwings were removed experimentally could still fly but could no longer turn sharply or accelerate, so the hindwing is essentially the manoeuvring surface. It also carries the eyespots and tails of species such as the eastern tiger swallowtail, which draw a bird's strike away from the body, a defence explained in the guide to butterflies with eyes on their wings.

The abdomen: breathing, digestion and reproduction

The abdomen is the soft, flexible rear part of the body, made of ten ringed segments that telescope slightly into one another. It has no legs or wings; it houses the organs that keep the animal alive and allow it to reproduce.

Along each side runs a row of spiracles, small valved openings leading into the tracheae, the branching air tubes that carry oxygen directly to every tissue. An adult has spiracles on the thorax and on the first seven abdominal segments; the older version of this page counted nine pairs on the abdomen alone, a figure closer to the caterpillar's total than to the adult's. Butterflies have no lungs, so the gentle pumping of a resting red admiral's abdomen is ventilation of the tracheal system.

Inside lie the crop, where nectar is stored, the midgut and hindgut, the Malpighian tubules that act as kidneys, the fat body that stores energy for migration and winter, and a tubular heart along the back that pushes clear blood, the haemolymph, forward through the body cavity. Some brush-footed butterflies also have a simple ear, Vogel's organ, at the base of the forewing, tuned to the low-frequency sounds of approaching birds.

The last two or three segments carry the genitalia: a pair of claspers in males, used to hold the female, and an ovipositor in females, through which eggs are placed one at a time on the host plant. Their shape is unique to each species and is what prevents close relatives from interbreeding, as described in the guide to how butterflies mate and reproduce.

Did you know?

Facts that surprise most people:

• Butterflies taste with their feet, smell with their antennae and hear, in a few species, with an organ at the base of the wing.
• A butterfly's blood is not red: it carries no haemoglobin and delivers nutrients rather than oxygen, which arrives through the spiracles.
• The wings, legs and antennae are fully formed inside the chrysalis before the adult emerges; they only expand.
• The same three-part body plan is shared by all of the more than 17,000 butterfly species, from the 58 recorded in the United Kingdom to the birdwings of New Guinea.

In summary

A butterfly's body is divided into a head, a thorax and an abdomen. The head carries two clubbed antennae for smell and balance, two compound eyes with UV vision, a coiled proboscis for drinking and a pair of sensory palps. The thorax, packed with flight muscle, carries the six jointed legs, reduced to four working legs in the brush-footed family, and the four scale-covered wings whose veins, cells and scales underpin every identification. The ten-segment abdomen breathes through paired spiracles and houses the digestive organs, the heart and the genitalia.

Frequently asked questions about the parts of a butterfly

What are the three main parts of a butterfly?

The head, the thorax and the abdomen. The head carries the antennae, compound eyes, proboscis and palps. The thorax is the muscular middle section to which all six legs and all four wings attach. The abdomen is the soft, ten-segmented rear section that holds the digestive, breathing, circulatory and reproductive organs.

How many legs does a butterfly have?

Six, in three pairs attached to the three segments of the thorax. In the brush-footed family, which includes monarchs, admirals, fritillaries and buckeyes, the front pair is reduced to small brushes held against the body, so these butterflies stand and walk on only four legs. Swallowtails, whites, blues and skippers use all six.

How many wings does a butterfly have?

Four: a forewing and a hindwing on each side, all attached to the thorax. The forewing is larger and produces most of the lift, while the overlapping hindwing controls turning and carries many of the eyespots and tails. A butterfly can still fly with its hindwings removed, but it can no longer make sharp evasive manoeuvres.

What do butterflies use their antennae for?

Mainly for smell and balance. The clubbed antennae are covered in chemoreceptors that detect flower scent, host-plant odour and mate pheromones, and Johnston's organ at their base senses airflow to help with orientation in flight. Migrating monarchs also use their antennae as part of the clock that keeps their sun compass accurate.

What is a butterfly's proboscis?

The proboscis is a hollow drinking tube formed from two half-tubes zipped together, coiled beneath the head when not in use. The butterfly extends it to draw up nectar, sap, fruit juice or mineral-rich water, since it has no jaws and cannot chew or bite. Its length is matched to the depth of the flowers each species visits.

How do butterfly compound eyes work?

Each compound eye is a dome of several thousand to about seventeen thousand tiny lenses called ommatidia, each looking in a slightly different direction. Together they produce a coarse mosaic image covering almost a full circle, with excellent movement detection. Butterflies also see ultraviolet light, revealing nectar guides on flowers and patterns on other butterflies invisible to humans.

Can butterflies taste with their feet?

Yes. The tarsi at the end of each leg carry chemoreceptors that read the chemistry of whatever surface the butterfly stands on. A female drums her front feet on a leaf to confirm it is the correct host plant before laying, and contact between a foot and a sugary liquid makes the proboscis uncoil automatically.

What gives a butterfly's wings their colour?

Tiny overlapping scales, tens of thousands per wing, each about a tenth of a millimetre long. Some contain pigments that produce blacks, browns, yellows and reds; others have microscopic ridges that scatter light to create structural blues and greens, which shimmer as the wing moves. Where scales are absent, as in the glasswing, the wing is transparent.

How does a butterfly breathe?

Through spiracles, small valved openings along the sides of the thorax and the first seven abdominal segments. They open into a network of air tubes called tracheae that deliver oxygen directly to the tissues. Butterflies have no lungs and their blood carries no oxygen, so the rhythmic pumping of the abdomen simply ventilates these tubes.

What is inside a butterfly's abdomen?

The digestive system, including the crop that stores nectar, the Malpighian tubules that act as kidneys, the fat body that stores energy, a tubular heart along the back, and the reproductive organs in the last two or three segments. Males have claspers for holding the female and females have an ovipositor for placing eggs on the host plant.

Published March 10, 2020 · Last updated September 21, 2026