Are Bees Really All That Busy?

Mental Floss, September 8, 2014 If idioms are to be believed, bees are some of the most industrious animals around. But it’s a little more complicated than poet Isaac Watts made it out be be when he wrote “How doth the little busy bee / Improve each shining hour, / And gather honey all the day / From every opening flower!” Some bees don’t really do any work at all, and are parasites of other bee species. These so-called “cuckoo bees” don’t collect pollen or build their own homes. Instead, they steal food from, and lay their eggs in, other bees’ nests. When the cuckoo bee larvae hatch, they eat their hosts’ pollen stores and sometimes their eggs if mom did not feast on them already. Other bee groups—the stingless bees, bumble bees and honey bees—are social insects that live together and work cooperatively. They put in honest work, unlike the cuckoo bees, but the amount of labor any one bee does varies with its role in the colony. The honey bee workers that forage food for the hive often do work “all the day,” like in the poem. Slate’s Forrest Wickman reports that these workers “spend nearly every hour of daylight outside” and entomologists have seen them making more than 100 foraging trips in a day. But these guys strictly work the day-shift, and come home to relax when the sun goes down. Meanwhile, other workers whose jobs keep them home tending honeycombs and cooling the nest work around the clock, but also take frequent breaks. “Drones, by contrast, are quite lazy,” Wickman says. “They don’t leave the hive until early afternoon, at which time they carouse around in packs, and when they get home just a few hours later, they rely on the worker bees to feed them.” Even among the foraging workers, the workload is not shared evenly and some bees are busier than others. New research suggests that it’s a small group of workers that do the bulk of the labor, while the others take it easy until conditions in the colony change and prompt them to get to work. For the study, researchers from the University of Illinois set up five experimental honeybee (Apis mellifera ) colonies—three in natural outdoor areas and two inside screened enclosures. Each hive was equipped with pairs of laser scanners at its entrance, and 100 to 300 workers from each colony were tagged with tiny micro-transponders. As these workers passed through the hive entrances, the scanners recorded the unique IDs of their tags, the direction they were traveling (that is, entering or exiting the hive) and the time of day. The setup allowed the researchers to track the workers as they came and went and tell how much time they spent out and about or in the hive, kind of like the time clocks that some businesses use to track employee hours. The scientists also used handheld scanners to record tagged bees’ visits to pollen and nectar feeders that they’d set up near the enclosed hives. After almost two months of gathering data while the bees went about their business, the researchers got a picture of the workers’ activity levels, and it showed that a small portion of bees were much busier than the rest. In all five hives, around 20 percent of the tagged workers accounted for half of the total recorded flight activity. These “elite” foragers, the researchers say, “began to make trips as soon as the colony became active each morning, and made regular, closely spaced trips throughout the day until the cessation of colony-wide flight activity in the evening.” The elite workers were not always busy, though, and their activity levels spiked and dipped over the course of the experiment and their lifetimes. That made the researchers think that the elite bees’ hard-working ways were not intrinsic, which team leader Gene Robinson says has always been the assumption with social insects, but adaptive. A worker might be more or less active in response to certain circumstances, like a favorite food source running low or new sources appearing. If the super foragers weren’t special, then maybe the other bees were not simply slackers, but more of a reserve work force also capable of elite behavior and just waiting for their time to shine. To see if the low-activity bees could and would step up their game when duty called, the researchers waited at the feeders near the enclosed hives during peak foraging time and captured all the bees that arrived there. While they could not specifically target known high-activity bees, the busier workers did have a higher chance of getting bee-napped because they made more trips. Sure enough, when the scientists checked the IDs of the captured bees and looked at their previous day’s flight records, most of the bees they removed were in the top 20 percent of the workforce. For the rest of the day after the cull, the feeders at both hives were quiet, with fewer than ten visits between them. The next day, though, foraging activity and the number of bees at the feeders returned to normal. The bees that had been taking it easy before were picking up the slack of their missing co-workers, some of them boosting their activity levels by almost 500 percent. The results, the researchers say, suggest that a hive is not divided into hard workers and slackers, but that every worker keeps tabs on the net activity of the colony and adjusts their own activity accordingly to make sure that the colony’s needs are being met.