Lights, camera - insects!

Hugh Aldersey-Williams finds the film of an AS Byatt novella more formic than formulaic

Charles Darwin opposed human slavery. But he could not help but admire what he called, in The Origin of Species, ants' "wonderful instinct of making slaves".

He was remarking on the propensity for some species of ant to capture and employ ants of other species for their own ends. The captured ants end their days serving the slave-making species.

The film Angels and Insects, based on AS Byatt's subtle novella Morpho Eugenia, plays upon such disturbing parallels between human and insect societies. The location is a Victorian country house just after the publication of Darwin's book. The household hustle and bustle is illuminated by the insect studies of a naturalist, William Adamson (played by Mark Rylance), who arrives as a guest, then marries the eldest daughter, Eugenia (Patsy Kensit).

Along with geology and astronomy, natural history was one of several fields where gentleman scholars - and significant numbers of gentlewomen - could play a real role in advancing scientific knowledge with comparatively modest equipment.

Yet the ant colonies described so enthusiastically by Darwin and his contemporaries still have secrets to tell. In research published in the science journal Nature last month, naturalists from the Zoological Institute at Frankfurt's Johann Wolfgang Goethe University report on an expedition to the Malaysian rainforest, where they found a bizarre new species of fly nesting in a colony of ants.

The fly disguises itself by dispensing with wings and legs to resemble the ants' larvae. "The flies and their larvae are fully integrated into the ant colony and totally deceive their hosts," say the researchers. It is thought they also produce ant-like pheromones to maintain the deception.

The German scientists' colleague, Henry Disney at Cambridge University, assigned the fly within an entirely new genus of the family Phoridae. Phorids are more diverse in both appearance and behaviour than perhaps any other insects, says Disney.

Phorids were first described in the late 18th century, but it was not until the end of the 19th that phorid parasites were found in association with ants and termites. The fictional Adamson would have known nothing of them.

"Females in the nests of ants and termites tend to be wingless. Hence there was great confusion as to what they belonged to," says Disney. "There were many misattributions." So different could the winged and wingless stages of some phorid species appear that specimens at different stages of growth would often be assigned not merely as different species, but to entirely different insect families. Disney cleared up the confusion only in 1992.

As Donald Feener of the University of Utah comments in Nature: "Deception and exploitation are common themes in the natural world. As in human society, a more sophisticated 'mark' requires a more elaborate confidence trick."

Although no character in AS Byatt's story is quite so devious as this, other insect metaphors recur throughout the film. The master of the house, the Reverend Alabaster, toils on a never-to-be-published volume that attempts to reconcile Christian certainties with Darwin's revelations. Like any drone, he produces nothing of use.

The enormous Lady Alabaster is constantly surrounded by parlour maids feeding her bonbons. "She is a marvellous symbol for an egg-bound female," says Christopher O'Toole, an entomologist at the Oxford University Museum who was a consultant on the film. When she dies, a black procession of mourners carries off her coffin like a column of ants. The servants of the household are the "slaves". Nursemaids for Eugenia's brood even reflect the fact that in ant societies, the slaves have exclusive care of the host larvae.

The deeper story explores the conflict between sexual selection and human passion. Adamson soon realises he has married the wrong woman. The brightly dressed Eugenia, though fecund and therefore useful in Darwinian terms for promulgating the species, offers no spiritual sustenance. Adamson finds solace in Matty Crompton (Kristin Scoff Thomas), a poor relation who serves as teacher to the Alabaster children, who is dully attired but intellectually alluring.

Shooting the film posed its own scientific challenges. Adamson builds a formicary to study life in the ant colony. O'Toole likewise had to establish a colony of slave-making ants and then simulate a raid in which these ants attack a neighbouring colony and carry off "slaves". O'Toole first laid down a slave-making ant trail using its pheromone. Then he placed a slave ant on the trail. The slave-making ants reacted on cue, raiding the slave ants' nest and carrying off larvae and pupae for the camera.

In another scene, Adamson woos Eugenia with a cloud of butterflies. That evening, he repeats the stunt with moths. Once again, pheromones were the key. "We got a whole load of sex-deprived males," says 0'Toole. "I dabbed Patsy Kensit's dress with pheromone and when we released them, they went berserk." The frail butterflies, temperamental as any film star, had to be bussed in from nearby butterfly farms and used for no more than two takes to avoid exhaustion.

'Angels and Insects' opened on Friday.

Christopher O'Toole's series on insect societies, 'Alien Empire', starts on BBC1 on 2 January.