Rare dual sex moth emerges at the Natural History Museum

Press release - 23 May 2008

A rare half male and half female moth has emerged today in the pupae nursery at the Natural History Museum’s Amazing Butterflies exhibition. The left wings of the gynandromorph* Antheraea frithi moth look female and the right wings look male, with a definite dividing line running along the moth’s body.

Moths and butterflies have a short life span, so visitors will be able to see this rare star at Amazing Butterflies for a short time only. It will then form part of the Museum’s world class, 9 million strong Lepidoptera collection.

The moth is not a biological hermaphrodite. In hermaphrodites, there is a fully functional set of both male and female sexual organs. In this moth, the female half has only a partial set of female organs and the male half has only part of a male set, neither part being functional.

Upon discovering the moth Amazing Butterflies butterfly house manager, Luke Brown, said ‘This is phenomenal and I am amazed to discover this moth. This is only the second gynandromorph moth or butterfly I’ve seen in ten years. And I’ve seen over a hundred thousand pupae hatch. We can only spot the amazingly rare condition in moths and butterflies because the males and females look very different from each other.’

Bilateral gynandromorphy like we can see in this moth can also been seen in crabs and lobsters. Each half of the animal has all the characteristics of its gender, right down to divided reproductive organs. It is caused when the two halves develop separately, due to a genetic error at the very beginning of the cell division process.

When a zygote (a fused sperm and egg cell) divides, eventually making all the different cells in the body, some cells become different from others and ultimately become muscle cells, nerve cells, intestine cells and so on. In some animals, including mammal and birds, cell division is initially indeterminate, meaning that the fate of the cells is not yet decided. However, in moths and butterflies, like all insects, each cell division from the very first is completely determinate, which means that decisions about what a cell will becomes are made straight away, not at a later stage in development. Most importantly, the first division into two cells separates left from right.

What sex an animal is gets determined by X and Y chromosomes. But, unlike humans, where the male is XY and the female XX, in butterflies and moths XX is male and XY is female. Normally, when a cell divides, the DNA is first copied and then a complete copy of the DNA is passed to each of the daughter cells. However, if the two DNA copies of the X chromosome do not detach in an XX male during the first zygotic division, then an individual can develop that is male on one side and female on the other side. This is what has happened to the moth at the Amazing Butterflies exhibition.

Dr Ian Kitching, Moth Researcher at the Natural History Museum, said ‘Gynandromorphs are incredibly rare. We only have 200 such specimens in our collection of some 9 million butterflies and moths. That’s equivalent to less than 0.01 per cent. The bilateral gynandromorphy that this moth shows is the result of an error involving the sex chromosomes at the first cell division. Sometimes, such errors occur later in development, whence the gynandromorphy is mosaic and the separation into the two sexes isn’t so clearly defined.

Amazing Butterflies visitor information
Opening times:
Monday to Sunday 10.00–17.30
Visitor enquiries: 020 7942 5000
Admission: £5, £3.50 concessions, £14 family (up to five, minimum one adult, maximum two). Free for Members, Patrons and children aged three and under.
Booking: www.nhm.ac.uk/amazing-butterflies
a £1.50 transaction fee per booking applies on all advance tickets
Nearest tube: South Kensington


Notes for editors

• *The term gynandromorph comes from the Greek gyn to mean female and the andro to mean male. It is a term usually used in the study of moths and butterflies or insects as a whole.
• The Entomology Department is one of six science departments at the Natural History Museum. The Entomology collections amount to 28 million specimens stored in 140,000 drawers. Scientists in the department study insects and other terrestrial arthropods, including spiders and mites in a wide range of research projects across the world.
• Butterfly stars of the entomology collection include the Idea tambusisiana from Sulawesi, which was described in 1982, has a wingspan of nearly 20cm (the same as a DVD case) and is one of the most spectacular butterfly finds of the last 50 years. Others include the celebrity Tanaecia pelea vordermanni from the obscure Indonesian island of Belitung, west of Borneo, named in honour of television personality Carol Vordermann’s father.
• Selected by Time Out in 2007 as one of the Seven Wonders of London, the Natural History Museum is also a world-leading science research centre. Through its collections and scientific expertise, the Museum is helping to conserve the extraordinary richness and diversity of the natural world with groundbreaking projects in 68 countries.

For further information, images or to arrange an interview please contact:
Claire Gilby, Natural History Museum
Tel: 020 7942 5106 Email: c.gilby@nhm.ac.uk