This amount should not, however, be disregarded, as damselflies are by no means the only predators of midges and other insects. This equated to around 1% of the total mass of the midge populations in the area. In the 12-hectare area we studied, the catch mass for the four species of dragonflies was about 900 grams, equivalent to about 700,000 medium-sized midges. During the period studied, the insect species consumed the most by the damselflies were different chironomids. The numbers of insects consumed, meanwhile, were estimated by covering certain areas with tent-like hatching traps and counting how many insects accumulated in them over a particular surface area, explains Senior Researcher Kari Kaunisto from the Biodiversity Unit of the University of Turku, who led the study.Ĭhironomids are damselflies' favourite foodĭragonflies are among the apex predators of the insect world and are considered to be responsible for regulating the numbers of many other insect species. By comparing the numbers of marked and unmarked dragonflies caught, we were able to estimate the total number of individuals in the area. We investigated the numbers of dragonflies by marking them with a series of numbers on their wings, releasing them and then catching them again. Population estimates of dragonflies were also obtained. The prey species of the dragonflies and their relative quantities were assessed by examining prey DNA extracted from the faeces of damselflies, using a method known as metabarcoding. The results of the novel study were obtained by combining multiple scientific methods. Although the numbers of prey species individuals hatching in the area is as much as one hundred times the quantities being consumed by the damselflies, the quantity consumed is nevertheless significant because there are many other predators also preying on the same prey species. A new study now sheds light on the role of dragonflies that occur in large numbers.Įven in just a small area, populations of matchstick-sized damselflies that whiz around, consume hundreds and thousands of insects. Who keeps numbers of insect in check during the summer? This has been debated for some time, but a clear answer has remained elusive, as it has been difficult to monitor the numbers consumed by different insect predators.
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