"Bee soup" made from hundreds of crushed up insects could paradoxically help ensure the essential pollinators' survival, say scientists.

The idea may appal animal rights campaigners but is the only way to provide accurate large-scale bee monitoring programmes based on DNA data, they claim.

Traditional methods of tracking bee populations involve pinning individual bees and identifying them under a microscope - which also kills the insects.

But this is too laborious and error-prone to allow the reliable tracking of bee populations across the whole of the UK, it is claimed.

Instead the researchers propose pulverising captured pollinators into a "soup" that can make their DNA instantly accessible.

By comparing the DNA sequences with stored genetic material known to belong to particular species, the identity of different bees can be discovered.

Professor Douglas Yu, from the University of East Anglia, who has tested the approach using "soups" made from 204 bees collected in the Chilterns, Hampshire Downs, and Low Weald, West Sussex, said: "Wild bees play a key role in pollinating wild plants and cultivated crops - maintaining both biodiversity and food production.

"They are however threatened by habitat loss, pesticides, climate change and disease. Safeguarding wild bee populations and their pollination services is therefore a top priority.

"Developing an efficient long-term monitoring programme to better understand the causes of their decline is one of the goals of Defra's national pollinator strategy. This will involve a massive collection of bees across the UK.

"Traditionally they would be pinned and identified under a microscope, but this is so labour-intensive and error-prone that the resulting data might not be available for years after the collections.

"We need more efficient identification methods if we are to improve our understanding of bee populations and their responses to conservation interventions. The big challenge is that there are hundreds of wild bee species per country, almost 300 in the UK alone.

"Even with the necessary expertise, it would be impossibly time-consuming to count and identify all the bees in each location, which is where the 'soup' comes in."

The technique enabled the scientists to estimated the biomass of each species put through the "soup test".

"The number of bees that end up in one of my soups is absolutely tiny compared with the populations being studied," Prof Yu added.

"Insect soup is a sensitive thermometer for the state of nature. And large-scale bee monitoring programmes would really benefit from this type of DNA sequencing. The method can easily be scaled up to track more species, like the 1,000 or so total pollinating insects in the UK.

"We can find out where species diversity or abundance is highest - for example in the countryside or in city parks - and how species diversity is affected by farming methods, for example, to see if habitat set-asides support more bees.

"Species biodiversity at any given site can be revealed in a single drop of soup. It's a technique that shaves weeks, months, years off traditional ecological methods, saves money and spares the need for tons of taxonomic expertise."

Results from the bee soup trial appear in the journal Methods In Ecology And Evolution.