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A talk by Dr. Ian Bedford.
(The John Innes Centre, Norwich)
Dr. Ian Bedford.
For our March meeting we welcomed Doctor Ian Bedford. Ian has worked at the John Innes Centre at Norwich for 42 years and now heads the entomology department there. His interest in insects started when he was a child, collecting butterflies.
Butterflies, together with moths, are members of the family Lepidoptera, insects having scaled wings. Fossil evidence reveals that they originated about 200 million years ago. Their life cycle is from egg to caterpillar, then chrysalis, and finally to adult. While in the chrysalis stage, true metamorphosis takes place where the cells completely disassemble and are then reformed into the adult. The caterpillar can eat between 27 and 29 thousand times its own weight.
What is the difference between butterflies and moths? Butterflies have club antenna, moths antenna are branched and feathery. Other differences: fly by day/fly at night; usually colourful/usually brown; lay eggs singly/lay eggs in groups; wing resting position folded above their backs/open at the side of the body; chrysalis hangs from a thread/spins a cocoon; bodies slender and smooth/stout and hairy. Just when you thought you’d cracked it – there are exceptions to all these comparisons.
It difficult to breed some species in captivity, but Ian mentioned that pushing them together had achieved encouraging results.
Butterflies communicate using visual and chemical signals. They see well in ultra violet and can signal by flashing their wings. The chemical pheromones can be detected by the antenna of the male from distances of up to six miles. Having mated, the female lays her eggs and then dies. In order to synthesise pheromones the butterfly needs to collect certain precursor chemicals, usually from decaying substances. The Purple Emperor is a particularly fine creature: there are groups of people known as Purple Emperor Fanatics, who have a special interest in that particular butterfly. In a kind of sport they concoct various ingenious attractants to lure the males. These have included a variety of dead animals, fox poo and the contents of a baby’s nappy – matured for a suitable period.
There are 58 British butterflies plus some migrants. Groups include, swallowtails, skippers, whites and yellows, browns and fritillaries, metalmarks, and coppers, hairstreaks and blues. One of the migrants, the painted lady, starts the breed season in North Africa, then, by a series of breeding cycles, migrates northwards through Europe into the arctic. Towards the end of the year kaleidoscopes of the species have been tracked by radar travelling in a southerly airstream at altitudes of between 3,000 and 5,000 feet back to Africa ready to repeat the cycle.
With regard to habitat there are generalists and specialists. Specialist habitats include meadow, heath and grassland, woodland glades, mountain, and wetlands. The balance of a habitat can be complex and delicate: ants look after the caterpillar of the Large Blue. The caterpillar secretes a sticky substance and makes a vibration, which is thought to trick the ants into thinking it has something to do with their queen. The ants feed the caterpillar, sometimes with their own young. The ants know when the caterpillar is about to pupate and look after it underground during that period. When the butterfly hatches the ants guide adult out of nest. During the process of pumping up its wings, the wings give off a sugary substance. While the ants clean this from the wings they are also providing protection from predators. The ants build their nest on the ground at the base of grass. If the grass is too high the humidity is not right and the ants will not survive. When rabbits got myxomatosis and died out, the grass grew, the ants died and in 1979 the Large Blue became extinct in Britain. In 2000 the rabbits, ants and butterflies were re-introduced into the Southwest of Britain from European stock. All are now doing well. One of our members remarked that at a SSSI in the forest near Hockham, a similar re-introduction project was being carried out using highland cattle to maintain the habitat required for certain species of dragonfly.
Still in Thetford forest, there is a colony of butterflies, the Silver Studded Blue. During the day the common black ant collects the caterpillars from wild legumes, take them down to their nest and protect them. At night the ants take the caterpillars out for a feed and look after them, then take them back again to the nest the following day.
Silver Studded Blue
In another example, Ian noticed a Holly blue flying around his garden. From time to time it was landing at various places on the grass. On inspection, at every spot where it had landed, there was an ant. The reason for all this behavior, as with so much else regarding butterflies, is not known.
Butterflies are having problems. Numbers have halved over the last 40 years and the White Hairstreak has declined by 96%. To thrive they need nectar rich plants, warmth from sunshine, shelter from storms, caterpillar food plants and a safe place to overwinter. They have natural enemies like predators, parasites, fungi, bacteria, viruses and bad weather. Unnatural problems like habitat loss, climate change and pesticides. Neonicotinoids, being systemic, are particularly problematic as the plant retains them for extended periods. Most chemicals are non-selective killing or affecting the life cycle of both good and ‘bad’ insects. Traces of neonicotinoids have been found on garden centre plants sold specifically to benefit butterflies. Some chemicals will eventually end up in rivers. Apparently, two of the most affected in the country are the Wensome and Waverny.
So how might we make our garden butterfly friendly? The planting of nectar producing plants is well known, but to provide for a range of butterflies with their differing breeding seasons there needs to be a variety of plants coming into flower throughout the year. Spring flowering: aubretia, cowslips and violets. For summer: honeysuckle, buddleia and lavender. In autumn: goldenrod, rudbeckia and sedum. There are many others. Stinging nettles are essential for some species. Your patch should be fairly large, in a sunny position and will require feeding from time-to-time. In winter? Over ripe fruit will be very beneficial. Avoid cutting down last year’s dead plants until spring so as to provide shelter.
A few years ago Ian decided to plant a dedicated butterfly garden. His wife was not keen on the idea as she has a dislike for all things creepy-crawly. Another wildlife essential his wife was not keen on was a water feature. In spite of differences of opinion both have now been built and have become a serious alternative to television. A most informative and entertaining presentation, accompanied by a wonderful slide show, ended with a question and answer session.
Competition results for March.
1 Sue Thomas.
2 Chris Dalton.
3 Val Long.
1 Jane Dalton.
2 Sue Thomas.
3 Chris Dalton.
1 Ed Szczepanowski.
2 Eric Rogers.
3 Sue Thomas.
This was the last indoor meeting of this season. Our next meeting will be on Wednesday 10thof April and will be to Didlington Nurseries. Leave Hockham village green at 13:35 for a 14:00 arrival. Having stocked up with copious amounts of reasonably priced plants we will travel on to the Bonsai Garden at Breckles; tour, talk and refreshments.
Page Last Updated - 16/03/2019