Millions of years ago, bees evolved from meat-munching wasps, but little is known about their transition from carnivorous insect to flower-seeking pollen-eater. A newly discovered fossilized bee, found frozen in time in amber from Myanmar, could shed some light, being the first record of a primitive bee with pollen.
Insects like bees are pollinators; as they journey from flower to flower in search of tasty pollen and sugary nectar, tiny yellow grains of pollen (basically the plant equivalent of sperm) attach to their bodies and are spread to the female reproductive structures of plants, allowing fertilization to occur. Without these six-legged pollinators, the plants would struggle to reproduce, and without the pollen and nectar they contain, the bees would go hungry. Pollinators and flowering plants have co-evolved over millions of years to develop their perfect partnership.
The bee trapped in amber, newly named Discoscapa apicula and described in the journal BioOne Complete, has pollen grains on its body, suggesting that it visited at least one flower before it met its sticky end 100 million years ago, during the mid-Cretaceous period. The bee belongs to a brand-new family, genus, and species.
"The fossil record of bees is pretty vast, but most are from the last 65 million years and look a lot like modern bees,” said Oregon State University researcher George Poinar Jr in a statement. “Fossils like the one in this study can tell us about the changes certain wasp lineages underwent as they became palynivores – pollen eaters."
It’s thought that pollen-eating bees first appeared around 130 million years ago, not long after flowers first evolved. In addition to being dotted with pollen grains, the fossilized insect bears another clue that it had been visiting flowers not long before it died; it shares its amber coffin with tiny beetle parasites, which still plague bees today. The fossils are the earliest evidence of these parasites ever found.
"Additional evidence that the fossil bee had visited flowers are the 21 beetle triungulins – larvae – in the same piece of amber that were hitching a ride back to the bee's nest to dine on bee larvae and their provisions, food left by the female," Poinar said. "It is certainly possible that the large number of triungulins caused the bee to accidently fly into the resin."
The bee trapped in amber shares certain features with today’s bees, such as body hairs known as plumose hairs, a rounded pronotal lobe on the upper part of its body, and a pair of spurs on its back legs. It also shares traits with apoid wasps, from which bees evolved, such as low-placed antennal sockets and certain wing-vein characteristics. But the insect has a unique feature too.
"Something unique about the new family that's not found on any extant or extinct lineage of apoid wasps or bees is a bifurcated scape," said Poinar. This means that the base of the insect’s antennae has two segments.
The bee, sharing traits with both the wasps it evolved from and the bees that exist today, is helping scientists better understand the evolutionary history of this iconic group of insects, 100 million years after it crash-landed into a blob of sticky tree goo.