La Brea Tar Pits yield exquisite Ice Age bees

Ancient pupae snug in leaves give clues to climate

NOW AND THEN A pupa of a modern leafcutter Megachile bee female (left) has the same basic look as a Megachile male (right, CT scan) that is at least 23,000 years old, having been preserved in the La Brea Tar Pits.

A.R. Holden et al/PLOS ONE

By Susan Milius

April 9, 2014 at 5:30 pm

It’s not all mammoths and saber-toothed tigers. The first leafcutter bees from the Pleistocene epoch have turned up in the La Brea Tar Pits in Los Angeles.

Exquisitely preserved as pupae undergoing their transformation to adulthood, a male and a female are still wrapped in their leafy nest. Micro-CT scans and other clues let researchers identify the bees as Megachile gentilis, a species that still lives today. These bees line burrows with bits of leaves to pamper developing offspring.

The preserved pupae probably lived between 35,000 and 40,000 years ago, says Anna R. Holden of the Natural History Museum of Los Angeles County. The bees’ presence suggest that the insects’ tar pit was near woods or riverbanks with pollen-rich plants in a relatively cool and moist climate, Holden and her colleagues report April 9 in PLOS ONE.