An even rarer dual-sex butterfly has hatched in the Natural History Museum's Sensational Butterflies exhibition, just 4 weeks after a half-male and half-female great mormon butterfly emerged.
The butterfly is a mocker swallowtail butterfly, Papilio dardanus, also known as a flying handkerchief, and comes from tropical Africa.
Volunteer Samantha Kenton found the 2nd dual-sex butterfly at Sensational Butterflies at the end of July.
It is rare enough, being a pure bilateral gynandromorph, with one side of its body female (on the left in the image above) and the other side male (on the right with the club tail).
But in addition, the female side of this butterfly is not the usual black and white colour, but a rare fully orange form.
Female mocker swallowtails have a remarkable 14 or more different forms, fully orange being one of the rarest.
These forms mimic inedible butterflies, which is a way of protecting themselves from predators.
Scientists have been studying this butterfly for nearly a century to try and find out why and how the diverse female forms occur.
Scientists at the Museum, including butterfly researcher Martijn Timmermans, are currently carrying out genetic and molecular research into these butterflies. ‘Papilio dardanus is a highly diverse and sexually dimorphic (males differ from the females) species. It’s exciting to see patterns of both sexes united in a single individual,' he says.
Butterfly house manager Luke Brown with the dual-sex great mormon butterfly, mid July 2011.
Timmermans hopes to get DNA from the butterfly. This should be quite easy as the butterfly was frozen almost immediately after it had died, which helps preserve it. ‘We will investigate the genetics that trigger the differences between the left and the right wing.’
Luke Brown, Sensational Butterflies butterfly house manager, explained how the butterfly find first came to his attention. 'I heard a squeal from the office and volunteer Samantha Kenton came running out with a butterfly cupped in her hands, rather excited.'
The specimen was found last week in the Sensational Butterflies exhibition, which is open until 11 September and has hundreds of live tropical butterflies.
Luke adds, ‘After 30 years of breeding tropical butterflies on a amateur and then professional scale, finding 2 gynandromorphs was quite something. Finding 2 more in 4 weeks shouldn't really happen!'
This female mocker swallowtail is the usual black and white form © Martin Thompson
Butterflies have a short life span and this butterfly has already died. It has been added to the Museum's world class Lepidoptera collection where it joins 4.5 million other butterflies, and around 200 other gynandromorphs.
Blanca Huertas, curator of butterflies at Museum, says, ‘The gynandromorph specimen of Papilio dardanus will enrich our collections. There are few examples there collected more than 100 years ago showing this phenomenon, which is undoubtedly rare but difficult to quantify.'
Sensational Butterflies entrance
Gynandromorphy in insects occurs if the sex chromosomes do not properly separate during division of a fertilised egg. It can also occur when an egg with two sex chromosomes, instead of the normal one, gets fertilised by two sperm.
Bilateral gynandromorphy happens when the sex chromosomes do not properly separate during the first cell division.
'Will there be another gynandromorph?' Luke asks. 'I don't know. Four are quite sufficient but my lucky number is 9 so bring on the next one!'