Butterflies & Moths

Butterflies and moths apart from birds, draw more interest than any other group of animals. Not only are these insects often very striking, but unusually for insects are easy to identify. Both butterflies and moths are insects belonging to the Lepidoptera; Lepis coming from the Greek scale and pteron meaning wing. This is the perfect description of the order, which is comprised of scaley covered winged insects.

There are no absolute characteristics that can be used to define the difference between moths and butterflies. The general rules of thumb being;

Moths fly at night while butterflies fly during the day.

Butterflies tend to be more vibrantly coloured than moths. Moths flying at night ( when it is dark ) have had minimal drive to evolve bright colours.

Butterfly antennas are club shaped, while those of moths are feathery.

It must be remembered that these are not firm rules and that there are common exceptions.

Life Cycle

Butterflies and moths have an interesting four stage life cycle; egg, caterpillar, pupa and adult. With a mortality rate, moths and butterflies have to lay a sufficient number of eggs to ensure the future of the species. The number of eggs runs into the hundreds. The eggs can be laid in large clutches or individually depending on the species.

At the egg stage it is often possible to differentiate the species, as the egg's shape and surface patterns are distinctive. However eggs by their nature are small and are laid hidden from the view of predators and are thus less often seen than the caterpillars and adults.

Eggs are generally laid in spring, near or on the food plant of the species, so on hatching the caterpillars have a readily available food supply. Caterpillars are basically eating machines, as they are required to increase their size over a hundred fold. They start eating straight away, their first meal being the remains of their egg case.

Their rapacious appetite is why, when they are in large numbers do considerable damage to plants. Numbers can be so high, that they eat out their food source and their numbers crash. Unlike the adult which like all other insects have six legs, caterpillars have additional legs, normally ten.

As the caterpillar grows it outgrows its skin and periodically has to shed it. Eventually the caterpillar will reach a stage when it has sufficient food stored in its body to carry it through its pupa stage. The caterpillar seeks a safe place hidden from predators, where it can go through the pupal stage. Then it sheds its skin for the final time and changes into a pupa. A butterfly or moth will eventually emerge from the pupa, which can be after a few weeks or in next spring depending on the species.

All moth and butterfly species have to find a way to survive the winter to breed next year. This overwintering depends on the species, it can be in the form of an egg, caterpillar, pupa or adult.

Hibernation

Some species hibernate overwinter as an adult, such as the brimstone and the small tortoiseshell.

Migration

There are butterfly species that migrate to Cornwall, a typical example being the painted lady and the large white. These migrate over the English Channel from Europe however this is not a true migration as it is only a one way trip, so really it’s an emigration.

Defence Strategies

Butterflies and moths like all creatures have their place in the food chain and hence have their predators. To reduce predation, differing strategies have evolved depending on the species;

Reducing the chances of being seen; by camouflage for example the scallop oak moth caterpillar which looks like a twig; or by the breaking up of their outline such as the ragged wings of the comma.

Some species do the opposite, having bright colours appearing to advertise themselves. These colours are a warning to potential predators, that they are toxic or bad tasting, good examples of this being the caterpillars of the cinnabar moth and adult tiger moths.

There are markings on some species that make them appear to be a creature that is more intimidating that they really are, for example two false eye markings on the elephant hawk moth caterpillar or the spine on the rear of a privet hawk moth.

Some caterpillars possess hairs that irritate predators and can even affect humans if handled, such as the caterpillar of the wooley bear tiger moth.

Butterflies such as the skippers have a fast and erratic flight, making it harder for predators to catch them.

Some caterpillars form a nest out of a rolled leaf and remain hidden, for example those of the mother of pearl moth.

Moths such as the red underwing have brightly coloured hindwings, which the moth when disturbed will quickly flash. This momentarily startles potential predators providing time to escape. When the moth lands it swiftly covers the bright hindwings, with only its camouflaged forewings showing, it appears to have suddenly disappeared.

Food Plants

Most species of moths and butterflies will only feed on a limited number of plant types, some only one plant. This limits the species to the ecological niche that the plant is found in. This excludes many species from this part of Cornwall. For example many plants require alkali soil types such as chalk downs, which are not found in the geology of Cornwall, hence excluded are the many species that solely rely on lime loving plants.