Beetles choose a balanced diet

Predatory beetles choose their food on the basis of its nutritional value, rather than just overall calorie content, according to new research published in Proceedings of the Royal Society B.

Scientists collected female ground beetles (Anchomenus dorsalis) from the wild and provided them with varyingly nutritionally balanced menus. The beetles that were provided with a range of foods selected the balance of protein and fat that was optimal for producing healthy eggs, going on to produce more eggs than the beetles that were not provided with the correct nutritional balance.

Previous research on insects has shown that herbivores such as butterfly larvae and grasshoppers and omnivores like fruit flies and crickets select food that will give them a balanced diet.  However, until now scientists have assumed that predators can only focus on obtaining sufficient calories in their diets. This is the first research to show that predators also select food on the basis of its nutritional value. Although this study focuses on one insect species, the researchers believe that this is likely to be true for predators across the animal kingdom.

Lead researcher Dr Kim Jensen of the University of Exeter said: “At a time of year when many of us are focused on healthy eating, it is interesting to see that predators are also selective about what they eat. Biologists have previously assumed that predators cannot afford to be fussy and that they are simply focused on getting the right quantity of food, rather than quality. We show for the first time that they do actually select the foods that will give them the right balance of nutrients.”