Although the colony sizes of most of these bees are much smaller than those of the European honey bee, the per-bee productivity can be quite high, with colonies containing fewer than a thousand bees being able to produce up to 4 liters (one US gallon) of honey every year. Probably the world champion in honey productivity, the "manduri" ("Melipona marginata"), lives in swarms with only about 300 individuals, but even so, it can produce up to 3 liters (.79 US gallon) of honey a year in the right conditions. One of the smallest among all bees in the genus "Melipona", with lengths ranging from 6 to 7 mm (15/64" to 9/32"), Is being used in some countries such as Japan and Germany as a pollinator for greenhouses. Although they do not tend to attack if not molested, when they feel the nest is under menace, these tiny bees' reaction is violent, and their strong jaws can penetrate human skin.