THUNDERBUGS have wreaked havoc across the county and cost the fire service thousands of pounds. The tiny black insects, also known as thrips, are less than one millimetre long but are still able to trigger smoke alarms linked to Cambridgeshire Fire and Rescue Service's control room in Huntingdon. The thrips crawl into smoke detectors, which mistake them for smoke particles and activate the alarm. In one eight-hour period last month, firefighters were called out to 15 false alarms - compared to 18 in the whole of July last year. The service has reported a four-fold increase on last month's figures for false call-outs caused by thrips. Last year, call-outs due to thrips cost the service more than \u00A311,000. Martin Brown, fire protection supporter officer at the service's headquarters, said: "The problem goes in phases and we had a bit of a mad session a few weeks ago. It links in with harvesting and weather conditions. If you get a prolonged period of hot weather, you might get two or three call-outs, not an unnoticeable figure. But get a humid period and you get a huge surge of them and there was a large number at the end of July." Mr Brown said the problem was not confined to any one area of the county but tended to affect the more semi-rural areas - where a higher density of businesses operated and backed onto open fields. He advised business owners - and home owners - to contact their alarm manufacturer or system manager to discuss ways to combat the problem. The fire service has been working hard to reduce the number of false alarms - caused by a variety of factors - and since 2006 has managed to reduce the annual figure from 4,600 to 3,600. Mr Brown said: "The other problem is if we have to send an appliance out to a false alarm that is one less appliance we have available to send to a real emergency. It could potentially put people in danger.