Butterfly Life Cycle & Anatomy

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The life cycle

The life cycle of butterflies and moths is divided into 4 phases.

The egg stage: the caterpillar eats it's way through the shell, many eat the whole shell to provide energy. The above movie shows the caterpillar eating it's way out of the shell.

The caterpillar stage: Feeding and growth phases, with moults to permit the body to expand. It is normally between 4-6 moults for most caterpillars.

The pupa stage: The body is extensively rearranged to form the adult moth or butterfly. Moths usually construct a protective cocoon in which to pupate. Some spin leaves to form a simple cocoon, whilst other's incorporate bark and wood to make an elaborate chamber. Butterflies are mostly suspended from leaves and stems. The caterpillar spins a silk thread to hang from.

The adult stage: As the pupa skin splits open, the adult begins to emerge and swallows air to expand the body. When fully emerged, the adult rest whilst pumping blood into the wings to expand and dry them.



The structure of a caterpillar.

The caterpillar head has simple eyes, two short antennae and strong chewing mouth parts. The body is made up of 13 segments. The first three segments behind the head are called the thoracic segments. Each of these three segments has a pair of jointed true legs. These become the legs of the adult butterfly or moth. The remaining 10 segments are the abdominal segments. These usually contain 5 pairs of false legs called prolegs. These are purely to support the growing body. Loopers have no prolegs whcih is why they have the characteristic "inchworm" method of moving. Small hooks called crochets at the bottom of the prolegs act as grippers. Spiracles are circular openings on each side of the body through which air passes in and out.

In order to survive many species have adapted behaviours in defence.Certain caterpillars have structures like fierce horns, which when disturbed will adapt an alarming 'stand up and stare' approach. Most swallowtail caterpillars possesss a protrudable forked scent gland called an osmeterium which emits a foul smell. Others ave spines which can cause rashes, these contain toxins, and although not fatal, can be very irritating. Some caterpillars have lumps called tubercles.




Britains Butterfly Year






Claspers The abdominal and anal segment legs.
Cocoon Protective casing around the pupa.
Dorsal Pertaining to the back.
Instar Stage between larval moults.
Larva (pl larvae) Second stage in a moth or butterfly's life-cycle during which all feed and grow, shedding skins about four or five times, until fully developed.
Pinacula Warts.
Prolegs Abdominal legs situated on the sixth to ninth and anal segments.
Prothoracic plate Structure on the top of the first segment.
Pupa (pl pupae) Third stage in a moth or butterfly's life-cycle, during which no feeding takes place and bodily liquids break down to reconstruct as the adult insect. Also known as the chrysalis.
Rings Body divisions or segments.
Segment Body divisions, the first three being the thorax, the others abdominal.
Seta (pl setae) Larval hair or bristles.
Spiracles Breathing holes along the sides of the larvae on the first and fourth to eleventh segments.
Subdorsal Pertaining to the area between the back and sides.
Subspiracular Area immediately below the spiracles.
Thoracic First three segments.
Tubercles Warts.