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MALE ladybirds are pretty stupid. They can spend up to four hours mating with a dead female before realising something is wrong. And if these cold-blooded creatures get caught in the act when the Sun goes down, the falling temperatures may leave them immobilised till morning. Such tales about one of the world鈥檚 most cherished insects might scandalise ladybird lovers. Yet they come from an ardent admirer who should know. Michael Majerus, a naturalist at the University of Cambridge, is the founder and coordinator of the Cambridge Ladybird Survey, an extraordinary study of the activities of ladybirds in Britain.

The survey started in 1984 as a casual request to amateur entomologists for more information on ladybirds to assist his research on sexual selection. From that, says Majerus, it developed 鈥渕ore by luck than judgment鈥� into one of the most exhaustive nature-watch campaigns ever, drawing in a diverse network of part-time ladybird spotters. Participants ranged from professional entomologists to primary schoolchildren, who all recorded their observations and sent them to Majerus and his small team of researchers and collators in the university鈥檚 genetics department.

As the survey鈥檚 network of recorders quickly grew to an estimated 30 000 people, so the information poured in. 鈥淭here鈥檚 so much data you can鈥檛 believe it,鈥� says Majerus. And much is valuable scientific information too, he insists. On the strength of the survey鈥檚 results, Majerus and his colleagues have produced several academic papers, which are all 鈥渜uite widely cited鈥�, and there are more in the pipeline, he adds.

The Cambridge survey soon overshadowed Britain鈥檚 official project, the Coccinellidae Distribution Mapping Scheme, which had been running since 1973 under the auspices of the Biological Records Centre at the Institute of Terrestrial Ecology near Huntingdon. And in keeping with the Cambridge team鈥檚 approach to popularising the campaign, Majerus recalls that its high spot was in 1990 when Linda Snell, a character in the radio soap opera The Archers, became the survey鈥檚 most prominent fictitious recorder.

But now the survey is winding down because Majerus can no longer afford the time to keep it going. Instead, he has accepted the part-time post of official ladybird collator of the Biological Record Centre鈥檚 scheme, and has been encouraging the Cambridge survey鈥檚 more experienced recorders to join him. Next week Majerus publishes the survey鈥檚 final report, a valediction that shows the survey to have been as ambitious as any formal investigation, even though its rules were not as stringent as those of more official schemes.

The Cambridge survey covered every facet of the ladybird鈥檚 year-long lifespan. Using 10-kilometre squares of the National Grid, recorders plotted the geographical distribution of different species, the favourite habitats and hosts, and what happened to the insects during winter. They also recorded some of the most startling aspects of a ladybird鈥檚 behaviour: the cannibalism and fratricide, the promiscuity and sexually transmitted disease, and the factors that lead to swarming, when ladybird 鈥渟tings鈥� are most commonly reported. As the survey tapped the enthusiasm of the public, 鈥渨e suddenly realised what a great resource there was out there鈥�, says Majerus.

Even researchers working for the Biological Records Centre, whose own study fizzled out in the wake of the Cambridge survey, acknowledge the value of the more popular initiative. 鈥淭he BRC had difficulty in getting enthusiastic recorders,鈥� recalls John Muggleton, a biologist at the Ministry of Agriculture, Fisheries and Food who ran the official scheme in his spare time until Majerus took over the post. 鈥淚t was always run in a small way, and with no funding.鈥� Majerus managed to generate enormous enthusiasm, he says, and had many more recorders sending in reports from areas that few people had studied, such as Scotland, Wales and the uplands of England. 鈥淚t was a matter of numbers.鈥� There were even recorders for the Cambridge survey scouring the 鈥渢ops of sycamore trees where no one had been before鈥�, he adds.

To ensure that his survey did not go the way of the official scheme, Majerus set its limits with care. He wanted to ensure the hunt for data remained an attractive proposition, both visually stimulating and intellectually feasible for rank amateurs and experienced professionals alike 鈥� an important consideration bearing in mind the insect鈥檚 genealogy.

Ladybirds are beetles, and so belong to the largest order of organisms on Earth, the Coleoptera. The ladybird family itself, the Coccinellidae or coccinellids, includes more than 5200 species, of which 42 species live in Britain. But not all of these British species have the bright colours and spots or patterning traditionally associated with ladybirds. 鈥淪ome are brown or black, and just 2 or 3 millimetres long,鈥� says Majerus. So, for the survey, he decided to ignore the more grublike members of the family, of which there are 18 species, and concentrate on the 24 species that most people would enjoy tracking and fewest would have trouble identifying.

As far as collation went, Majerus accepted data from anyone prepared to provide it, even young children. In fact, he recalls, young science undergraduates have said 鈥渢hat their interest in biology was first kindled by studying ladybirds for the Cambridge Ladybird Survey鈥�. But he rigorously sifted out those reports where, for instance, locations were not recorded precisely enough or identification relied solely on the number of spots on the insect鈥檚 back.

Spot check

One of the survey鈥檚 great successes was to record the 5-spot ladybird (Coccinella 5-punctata) for the first time since the early 1950s. In 1987, the species was discovered in one of its few old haunts, in the Spey valley in Scotland, and then in Wales for the first time ever, living on unstable river shingles in Dyfed. Until then, the 5-spot had been considered extinct in Britain. A disappointment, or 鈥渇ailure鈥� as Majerus chooses to describe it, was that the survey did not turn up a single confirmed sighting on the British mainland of the 13-spot ladybird (Hippodamia 13-punctata). In 1991, the Nature Conservancy Council decided that the 13-spot was extinct in Britain, but Majerus believes it will turn up again.

For Majerus, a perk of being involved in popularising the insects was to be asked by the Royal Society for Nature Conservation to invent common names for the larger and more brightly coloured species of British coccinellids 鈥� those that young naturalists would immediately identify as ladybirds. So Britain now has ladybirds that go by the names of cream-streaked, kidney-spot, heather, pine and larch.

The Cambridge survey turned up few real surprises, but Muggleton points out that in some ways this enhances its value. It means, he says, that professional naturalists can have some confidence in the unexpected results that it did reveal. For example, several species were discovered in places where they would not normally be expected to live. Eyed ladybirds (Anatis ocellata), striped ladybirds (Mysia oblongoguttata), cream-streaked ladybirds (Harmonia 4-punctata) and larch ladybirds (Aphidecta obliterata), which are all conifer specialists, turned up on deciduous trees, such as oak, sycamore and maple.

Majeius offers a simple explanation. These sightings were made towards the end of the summer, and involved only young ladybirds (given away by their paler colourings) preparing to hibernate for the winter. They must feed up before the winter, he says, and will seek food on whichever trees sustain a supply of aphids, or other prey.

Such instincts help to explain the bizarre phenomenon of ladybird swarms and the reports of humans being bitten by the insects; a ladybird bite injects a pre-digestive enzyme that generates a stinging sensation as the human body mounts its biological defence. They even resolve the mystery of how some species seem capable of accurate long-range weather forecasting; if a ladybird is undernourished late in the year, it might as well risk a search for food and hope for a mild winter as starve while hibernating, says Majerus. So if hungry ladybirds do happen to survive winter because the weather is mild, we like to see them as potential stand-ins for Michael Fish, even though they have simply just been lucky. Not to put too fine a point on it, says Majerus, all three types of behaviour come down to the insects feeling hungry.

The changing food supply explains the great swarms of the hot English summer of 1976, when billions of ladybirds descended on coastal resorts in late July and early August. This followed a mild winter that allowed most of the previous season鈥檚 ladybirds to survive into the new year, and a wet spring that produced lush plant growth and a population explosion of the aphids on which ladybirds feed. Through the spring and early summer, the ladybirds were able to gorge themselves and reproduce furiously. But by the middle of July the aphids had been eaten up and, worse still, their host plants had withered in the scorching heat. In their search for food, the ladybirds flew farther and farther afield until they reached the coast. There, amid reports that they were 鈥渟tinging鈥� or 鈥渂iting鈥� humans, the ladybirds drove holidaymakers from the beaches. 鈥淚n truth, all the poor starving things were doing was trying to find food,鈥� says Majerus. 鈥淚n their desperation, they tested the edibility of anything that might have been nutritious to them.鈥�

False alarm

In early 1990, a growing volume of survey data convinced Majerus that Britain was in for its 鈥渂est year for ladybirds since 1976鈥�. But the ladybird invasion never materialised, a fact he puts down to late frosts, the dullest June for more than 30 years and attacks by parasites or predators that happened to mature in time to enjoy a later generation of ladybird pupae. Nevertheless, he says, 鈥渨e did discover a good deal about some of the natural enemies of ladybirds.鈥�

Majerus describes the Cambridge campaign as 鈥渢he most successful survey of the natural history of a small group of insects that has ever been undertaken anywhere in the world鈥�. Independent observers may show a touch more restraint, but few seem to doubt its importance. The survey has provided 鈥済ood scientific information鈥�, agrees Bob Pope, a semi-retired ladybird specialist at the Natural History Museum in London. 鈥淚ts value outside Britain is that it will give guidance to other groups on how to undertake similar studies.鈥�

Almost as impressed is the head of the Biological Records Centre, Paul Harding. The Cambridge survey, he says, 鈥渉as been very successful at doing what it set out to do for this small but attractive group of insects鈥�. He points out that ladybirds are not just pretty to look at. 鈥淪everal species of ladybird are of some real economic importance,鈥� because of their appetite for aphids such as greenfly and blackfly, which feed on plants.

Whether the venture could be repeated for less homely creatures is another story, says Harding. Take the earwig and the millipede. 鈥淓veryone knows what they look like, but they鈥檙e not very popular and the distribution maps show we have relatively few records for them.鈥� Mapping their lifestyle will have to be done by professionals or not at all.