In the south, they feed over lakes and farmland, and their diet varies accordingly, including dung -beetles, moths, and caddis flies as well. Around midsummer in northern localities, the sun is below the horizon for only one and a half hours each night. Hence, bats have to fly in twilight conditions, and even in sunshine, to cover their energetic needs. I have observed sparrow hawks attacking northern bats on a few occasions, and in one case, the bat was actually caught and eaten. Mosquitoes are certainly abundant enough in the northern taiga to support many bat colonies in summer, and with such abundance, bats are able to consume vast quantities very quickly.
Summer nights are often cool at high latitudes, and northern bats avoid flying at low temperatures.
In fact, they do not emerge to feed at all unless the evening temperature is above 45 degrees F because most insects are inactive at lower temperatures. Those that still fly are not numerous enough for bats to harvest efficiently. Regardless of how hungry a bat is, flying at low temperatures uses more energy than is gained from captures, so staying in the roost is probably the best option. Summer cold spells are common in Sweden and sometimes prolonged as well, particularly in the north. Unfortunately, small mammals like bats cannot stay warm and active for more than a few days on stored fat.