In a flutter over pink
QUESTION Earlier this year, I believe I saw a pink butterfly. The Woodland Trust said this was biologically impossible. Was I mistaken?
IT’S not impossible, but highly unusual. In 1994, Stratford Butterfly Farm made headlines when it successfully bred 20 pink specimens of the cabbage white, Pieris
brassicae. This was the first confirmed case of a pink British butterfly. In this case, the pink colour appeared to be the result of a natural mutation.
There had been unsuccessful attempts in the past to produce pink butterflies artificially by exposing the insect’s chrysalis to chlorine vapour or by adding dye to the food of the caterpillars.
David Carter, an entomologist at the Natural History Museum who was in charge of the nation’s butterfly collection at the time, was surprised. ‘At the museum we have about half a million specimens of British butterflies and moths and we have no pinks,’ he said.
It was surmised the butterfly was the result of a rare mutation that produces the pink coloration only when a butterfly has two copies of the defective gene.
The mutation did not affect the caterpillars, which were the normal green/ yellow. The chrysalis, however, were a deep reddish pink, rather than the usual greenish white.
Given the rarity of such mutations, it is possible that you saw a moth rather than a butterfly. A good candidate would be the rosy footman ( Miltochrista miniata), a very attractive moth, almost butterflylike in appearance with orange or pinkish forewings, crossed by a curious black wavy line. It appears in woodland in the southern half of Britain, but is more common in the southern seaboard counties in July and August. Another is the ruby tiger ( Phragmatobia
fuliginosa), common across Britain. It displays more vibrant colours in the South, where it flies in April to June, and again in August and September. Other moths that display some pink on their wings are the elephant hawk-moth ( Deilephila elpenor) and the small elephant hawk-moth ( Deilephila porcellus), but you are unlikely to mistake these for a butterfly.
Gareth Maybe, Frome, Somerset.
QUESTION In the 1953 western Shane, the farmers celebrate Independence Day with a dance in which they sing: ‘Goodbye Old Paint, we are leaving Cheyenne, we are going to Montan(a) . . .’ What were the origins of this song and what was Old Paint?
THIS is a variant of the traditional cowboy song I’m A-Riding Old Paint: ‘I’m a-riding old Paint, I am a-leading old Fan / I’m goin’ to Montana to throw the hoolihan.’
Old Paint is the name of the cowboy’s saddle horse, and Fan is his pack horse carrying all his belongings.
In Britain, we call black-and-white horses piebald and brown and whites are skewbalds. In the southern U.S., a piebald is often referred to as a Pinto, from the Spanish for paint.
‘Hoolihan’ refers to bringing down young cattle to be ‘ thrown’ — i. e. restrained for branding. Paint refers to the horse’s two colours. Andrew Perrins, Upton-upon-Severn, Worcs.
QUESTION Would World War II planes such as the Spitfire and Lancaster have gained extra performance if they had the upturned wing tips seen on many modern aircraft?
THe Lancaster probably would have gained slightly from upturned wingtips, also known as tip fins, but not enough to make them worthwhile. They would not have been beneficial on the Spitfire and could have been a disadvantage.
Wingtips are a problem because of the difference in air pressure between the upper and lower surfaces of the wing. At the tips this pressure difference causes air to flow from the underside of the wing to the upper surface.
This reduces the lift generated by the outer section of the wing and creates a vortex that can be seen under humid weather conditions streaming back from the wingtips. They also show up well if the aircraft flies through a cloud. The simplest way to improve the performance of the wing is to make it longer so that the inefficient tips are a smaller proportion of the whole wing. Modern airliners have noticeably longer and thinner wings than older models.
Longer wings need stronger materials and there is the practical problem that the aircraft takes up more space on the ground and needs a larger hangar.
An alternative solution is to fit fins to the wingtips. These reduce the amount of air flowing around the tip, increasing the efficiency of the wing and reducing the strength of the vortex. On a modern airliner, this can result in a fuel saving of 5 per cent, significant on long routes.
A Lancaster bomber with its piston engines and gun turrets is not as streamlined as a modern jet airliner, so the drag from the wingtips is a smaller proportion of the total drag, and fitting tip fins would not be so beneficial.
Tip fins have to be designed using lots of mathematics — if the designer gets it wrong, then the performance of the aircraft can be degraded.
The Spitfire and similar aircraft have to be extremely manoeuvrable and fast — long, thin wings or the weight of tip fins would reduce its rate of roll. In redesigns, the wings were reduced in span to improve its speed and rate of roll.
With small aircraft, ground handling or hangar size is not usually a problem, except on aircraft carriers, where the usual solution is to make the wings capable of being folded.
No modern fighter aircraft have been designed with tip fins.
Denis Sharp, Hailsham, E. Sussex.
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