Wednesday 2 September 2009

Butterflies and Buddleia

September is upon us and another summer is gradually drawing to a close. One of the memories I shall take from this summer is the number of butterflies that have visited the garden. Despite the amount of wet weather we have experienced in recent months, the butterflies have not only survived but thrived. Several years ago we planted two buddleia bushes in the garden, with the sole intention of attracting butterflies and they have been arriving ever since. We all see and enjoy butterflies but do we know much about them? Here are some interesting facts:

Butterflies are notable for their unusual life cycle with a laval caterpillar stage, an inactive pupal stage and a spectacular metamorphosis into a familiar and colourful winged creature. Butterflies are important as agents of pollination, whilst a few species are pests, because they can damage domestic crops and trees in their larval stage. The lift generated by a butterfly is achieved by using a wide variety of aerodynamic mechanisms, these include wake capture, vortices at the wing edge, rotational mechanisms and clap-and-fling mechanisms. They are able to change from one mode to another very rapidly.
It is a popular belief that butterflies have very short life spans. However, depending on the species some butterflies can live for up to a year. Butterflies may have one or more broods per year.
Butterfly eggs consist of an outer shell containing a thin lining of wax to prevent the egg from drying out before the lava has developed. Each egg is fertilized through tiny funnel-shaped openings at one end of the egg. Butterfly eggs are fixed to a leaf with a special glue. The egg stage lasts for a few weeks. Depending on the species eggs may be laid just prior to winter, to hatch in spring. Others lay their eggs in spring to hatch during the summer. From the eggs emerge caterpillars, which mainly spend their time consuming plant leaves although some species are insect eating. Caterpillars mature through a series of instars. Near the end of each instar the caterpillar undergoes a new change in its development as a butterfly. Development of butterfly wing patterns begins by the last larval instar. When the caterpillar is fully grown it stops feeding and begins wandering in its quest to find a suitable pupation site, often under a leaf. The caterpillar transforms into a pupa or chrysalis by moulting for the last time. The pupal transformation into a butterfly through metamorphosis has held great appeal to mankind.
The adult butterfly has four wings covered with tiny scales. The fore and hind wings are separate, permitting a more graceful flight. As the butterfly emerges from the pupa it has to unfold and inflate its wings before it can fly.
The body of the butterfly is made up of three segments. The head, thorax and the abdomen. They have two antennae, two compound eyes and a proboscis. The coloration of butterfly wings is created, not by pigment, but by the microstructure of the scales. This structural coloration is the result of coherent scattering of light by the photonic crystal nature of the scales.
Butterflies feed primarily on nectar from flowers. Some derive nourishment from pollen, tree sap, rotting fruit, dung and dissolved minerals in wet sand or dirt. Some species are attracted to sodium in salt and will sometimes land on people attracted by human sweat.
Many butterflies, such as the Monarch, are migratory and capable of long flight. They migrate during the day, using the sun to orientate themselves. The Monarch butterfly will migrate from Mexico to North America, over 2,500 miles. Butterflies are also territorial and will attack other butterflies invading their patch. Basking is common in the cooler hours of the morning. Many species will orient themselves to gather heat from the sun.
Perhaps after reading this article you may see butterflies in a different light. Don't forget to plant those Buddleia shrubs in your garden, they grow very quickly, I guarantee next summer you will have a garden full of butterflies.
Butterflies Pictured (from the top): Cabbage White, Giant Swallowtail, Red Admiral, Regal Fritillary.
Photographs reproduced by kind permission of Jay Cossey http://www.photographsfromnature.com/