Bigger bees have larger brains and are better pollinators.

Living in cities has an impact on bumblebee size. Bees are larger in urban areas and, because of their increased heft, they’re more productive than their rural relatives, according to new research.

City life has advantages and disadvantages for bumblebees. Gardens, yards, and parks offer lots of potential food sources. However, cities are warmer than rural areas and bumblebee habitats are broken up by long stretches of concrete and building, causing fragmented environments.

A team of biologists from Germany’s Martin Luther University Halle-Wittenberg (MLU) and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig were curious about how urban development affects bumblebee evolution. They collected more than 1,800 bumblebees from nine German cities and their corresponding rural surroundings. All the urban locations were botanical gardens and parks full of flowering plants. The rural sites had a buffer of at least 6.2 miles (10 kilometers) from the urban sites, had a low density of roads, and were filled with semi‐natural vegetation.

The biologists focused on three species abundant in the area and widespread in Europe: the red-tailed bumblebee (Bombus lapidarius), the common carder bee (Bombus pascuorum), and the buff-tailed bumblebee (Bombus terrestris).

At each site, the researchers placed potted red clover plants — a bumblebee favorite. They left the plants in each location for five days as a reference for pollination.

At the end of each period, the researchers used a hand net to collect as many bumblebees as they could from each species. They measured the body size of each bee they caught and also counted the average number of seeds produced per each red clover plant in each location.

Their findings, published in the journal Evolutionary Applications, showed that bumblebees from urban areas were larger than their rural counterparts by about 4%. The results were similar for all three species.

The difference in body size may be due to the fact that the bumblebees’ habitats in urban areas are becoming increasingly fragmented.

For more info read the full article on TreeHugger.