"Although non-bees were less effective pollinators than bees per flower visit, they made more visits - thus these two factors compensated for each other, resulting in pollination services rendered by non-bees that were similar to those provided by bees," they found.
They also concluded from the studies that measured fruit set that this increased with non-bee insect visits independently of bee visitation rates, suggesting that other insects provide a benefit separate to that from bees. They also appear to be less reliant than bees on having a suitable habitat in the surrounding landscape.
One of the researchers, Brad Howlett of New Zealand's Plant & Food Research, said: "It's vital that when we consider pollination services for our commercial crops we don't forget about these other insects as effective pollinators." The results were published in the US-based Proceedings of the National Academy of Sciences.