Lepidoptera (butterflies and moths)

Lepidoptera fast facts

  • Lepidoptera (butterflies and moths) are holometabolous insects; that is they have four distinct stages in their lives, egg, larva, pupa and adult
  • In each stage they look very different, and two of the stages are largely immobile, resting stages
  • There are around 165,000 species known worldwide, but it is believed that there could be double this number as many are waiting to be discovered and many to be described. There are 8,500 species in Europe and 2570 in the British Isles, but only 67 of these British species are butterflies; the rest are moths. Click here for species featured on this site.
  • Of all the species in the world only around 2000 are butterflies; the rest are moths
  • The adults are clothed with scales often of bright colours. The scales are modified, flattened hairs.
  • Most adults have a suctorial proboscis (tongue), and biting, chewing mouthparts in larva
  • They have chemoreceptors for taste and smell on their legs as well as on their mouthparts
  • Adults have large compund eyes
  • Jumping beans are actually milkweed seeds with the caterpillar of Carpocapsa saltitans, also known as Cydia deshaisiana, inside. The convulsive movements of the caterpillar to avoid heat cause the jumping.
  • The tequila worm is actually a caterpillar in the Megathymidae family. The worm acts as a simple form of quality control. If the worm is well preserved then the alcohol concentration of the tequila is sufficiently high, if not then the tequila has a weak alcohol concentration, or has been adulterated in some way.

Main differences between butterflies and moths

The differences above are rough guides. There are day flying moths (e. g. the 6 spot burnet), and there are butterflies that rest with their wings open (e. g. the Goliath birdwing).

Butterfly and moth eggs

The drawings below show the eggs of:

1 Catocala nupta, the red underwing moth. The eggs are laid either singly or in small groups in crevices on the bark of willow, poplar and plum trees. They hatch the following spring and the caterpillars feed at night hiding on the bark during the day. They are fully grown by June or July; pupate in cocoons spun between leaves or in bark crevices and the adults emerge in August or September.

2 Pieris brassicae, the large white butterfly. In the UK there are two generations a year. The eggs are laid in batches on the underside of the food plant; cabbage, and other related plants. The eggs hatch in about a week, and initially the caterpillars feed together.

3 Catocala fraxini, the Clifden nonpariel. Rare in the UK, but found widely in Eurasia. The eggs are laid on poplar, the larval food plant.

moth and butterfly eggs


Below is the typical caterpillar body plan usually there are 13 segments including the head. The head segment is the only part encased in hard chitin. Caterpillars do have antennae, but they are so small as to be barely visible.

caterpillar digestive tract

The foregut is where the food is mixed with the swallowed saliva, and where the salivary enzymes start the digestive process. The midgut is the main site of digestion and absorption.

The hindgut resorbs water from the faeces. Because plant cell walls have a high proportion of indigestible tissues, e.g. cellulose and lignin, and a low nutritive content, the digestive tract occupies a large proportion of the body cavity.

caterpillar body

The spiracles are the openings through which the caterpillar breathes, below is a close up of a spiracle of an Elephant hawkmoth caterpillar.

spiracle of caterpillar

Caterpillars are eating machines. They are little more than a mouth and an anus connected by a bag containing the gut. From hatching from the egg to the resting stage just before pupation a caterpillar can increase its weight by as much as 10,000 times.

Caterpillar legs

caterpillar legs

A caterpillar has three pairs of true legs at the front of the body and the other legs which are called prolegs towards the rear.

The number of pairs of prolegs varies according to species. Above is a drawing showing the differences between the two types of leg. The proleg is soft, fleshy and surrounded by a circle of hooks.

Eyes. Caterpillars do not have compound eyes; they have a number of simple eyes (ocelli) on the sides of their head. These eyes can probably just detect light, dark and movement.

Chrysalis, pupa, cocoon

chrysalis of butterfly

Above is the typical chrysalis. This is of a cabbage white butterfly.

Silver y cocoon

Above is the cocoon of the Silver Y moth.

Ghost swift moth cocoon, Hepialus humuli cocoon

Above the cocoon of the ghost moth.

Before the caterpillar moults into the chrysalis stage it will stop feeding and search for a suitable place, this may be on the food plant or underground or on a wall. This is why you may find a large caterpillar wandering around far from its food plant.

When the adult emerges from the chrysalis and is drying off a drop of red/vermillion fluid is often secreted from the anus. This is called the meconium, and is the stored excretory products of the chrysalis with much of the water removed. Drops of meconium produced in great numbers from butterflies in trees have given rise to legends of "showers of blood".

adult butterflies and moths - caddis flies and moths

Related pages