Bumblebees bite plants to help them bloom
Just a helpful nip.
When their pollen supply runs short, bumblebees bore tiny semicircle-shaped holes in the leaves of flowering plants, causing blooms to appear weeks ahead of schedule. Bee-bitten plants bear flowers about two weeks to a month sooner than untouched plants, according to a new study. Researchers attempted to recreate these bee-bite patterns using metal forceps and a razor, but even then the damage inflicted by bees boosted flower production more effectively than the scientists could; bee-bitten plants bloomed eight to 25 days before the artificially damaged ones did, depending on the plant species.
In early experiments, buff-tailed bumblebees (Bombus terrestris) appeared to ramp up this biting behaviour when deprived of pollen, a key food source for both bee larvae and the worker bees themselves. To test the hypothesis the research team deprived one group of worker bees of pollen for three days, while a different group was provided with abundant pollen resources. When released into enclosures full of flowerless tomato and black mustard plants, the deprived bees began nibbling at the leaves with gusto. The satiated group, in contrast, inflicted only minor amounts of leaf damage.
To confirm that the hungry bees weren’t simply eating the leaves, or carrying bits back to their hive, the authors placed paper cones beneath the plants to catch falling debris. Leaf bits accumulated in the cones, and no leaf residue appeared back at the hive, they noted. The bee-inflicted damage resembles tiny half-moons – carved by the insects’ mandibles – or pinprick holes poked out with their proboscises, their tubular mouthparts.
The team observed this biting behaviour in both their laboratory bees and wild colonies. In the wild bees the team noted that biting behaviour dropped off once the outdoor plants began to flower, bolstering the idea that the bees damage leaves when their available pollen supply runs low.
While several species of wild bumblebees, including B. terrestris and B. lucorum, ravaged the flowerless foliage, honeybees and common furry bees that visited the roof would not. But why would only bumblebees beat up plants to boost their flower supply? That the scientists don’t know yet.
If cues from bees can accelerate flowering, “scientists might realise a horticulturist’s dream by deciphering the molecular pathways through which flowering can be accelerated by a full month,” said Lars Chittka, a professor of sensory and behavioural ecology at the Queen Mary University of London. NICOLETTA LANESE