Caterpillars

Emerging from a tiny yellow/green egg a minuscule large white caterpillar (Pieris brassicae) clambers out into a world of green. As far as his compound eyes can see, a slightly hairy green carpet surrounds him. He lowers his head and uses his new mandibles to scrape off a layer. He likes it. Eating more, the tiny caterpillar continues to grow, surrounded by his brothers and sisters as they move about the leaf in a communal group. As the little caterpillar moults he grows larger and larger until eventually he sees bright orange flowers in his world. He is settled on a Nasturtium plant. He sees vague shadows of large creatures wandering by, students going about their business on the Penryn campus in Cornwall.

Large White (Pieris brassicae) caterpillar

Eventually the little caterpillar has gone through a series of life stages, called instars, and now doesn’t feel hungry anymore. He now feels like it’s time to move off the nasturtium bed and across to a nearby tree. Climbing up the tree he reaches a point at which he spins a special string of silk. With this silk he makes a small hammock for himself and attaches the ends to the trunk of the tree. He now begins the process of metamorphosis.

Knot Grass moth (Acronictus rumicus) caterpillar

Across the campus the same is happening to a lavishly decorated knot grass moth caterpillar (Acronictus rumicus) in the Walled Garden of the University.

Dot moth (Melanchra persicariae) caterpillar

On a shore path between coves near the seaside town of Falmouth, the cryptically camouflaged Dot Moth (Melanchra persicariae) caterpillar is sat on her Bracken frond, biding her time before pupating.

Eyed Hawkmoth (Smerinthus ocellata) caterpillar

Barely 5 miles from Land’s End a stocky Eyed Hawkmoth caterpillar (Serinthus ocellata) is climbing down a tree, ready to bury herself in the leaf litter until spring.

Inside each of these caterpillars, an amazing transformation is just about to occur.

During each instar the hormone ecdyson is released, triggering the caterpillar to shed its skin and grow larger. A second hormone - Juvenile hormone- prevents ecdyson from triggering full scale metamorphosis by inhibiting the ecdyson protein's active site preventing hormone receptor complexes from forming. The juvenile hormone is stimulated to be released when ecdyson levels become too high and, when ecdyson levels decrease, juvenile hormone stops being released in a process known as negative feedback. When Juvenile hormone runs out, the caterpillar undergoes full metamorphosis.

When metamorphosis begins the caterpillar's internal cells are digested by enzymes called Capases. Capases break down the caterpillar's cells into multiple copies of a single polypeptide. This polypeptide is the protein rich soup needed to fuel the rapid cell division needed to form all the features of an adult butterfly or moth.

This incredible process basically allows a caterpillar to turn itself into a protein rich soup and the reassemble itself into a creature with amazingly different characteristics and features!

The once little Large White caterpillar has now emerged as a butterfly. He fills his wings, flaps, and rises above his nasturtium filled world. He can see right across the landscape. From the university campus to the twin lakes to the glistening sea in the distance. He sets off to find a mate and to begin the cycle of the Large White butterfly again.

Large White - Pieris brassicae