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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Oil bees, if you please: Centris nitida


Powerful jaws grasp the base of a flower petal providing traction necessary for Centris nitida to collect floral oils from the Stigmaphyllon blossom. Photo credit: Dr. Paula Shrewsbury


During the last month we met several friendly and not-so-friendly visitors to the Sunshine State from foreign lands, including gorgeous green orchid bees, beneficial air potato leaf beetles, and cycad-killing armored scales. This week we return to beautiful Selby Gardens to meet yet another non-native insect that may contribute in a positive way to the sustainability of our native plant and insect communities.  Centris nitida, a native to South and Central America, was first discovered in Florida in 1997. Like other members of the genus Centris, in addition to gathering nectar and pollen to feed its young, this bee visits oil-producing plants to gather floral oils. As I watched these delightful bees, I was puzzled by their intimate interaction with the reproductive structures of the Stigmaphyllon plant. Rather than collecting pollen from the anthers or sipping nectar from the blossom, bees grasped the base of a flower petal with their jaws and vigorously stroked floral structures with their legs. What was the purpose behind this unusual blossomy cha-cha? Some plants visited by Centris produce oil from specialized glands called elaiophores lining the surface of their blooms. These furry fliers have specialized hairs on their front and middle legs shaped like butter-knives and spatulas. The hairs rupture oil-bearing plant cells, releasing the precious fluids which are then transferred to the forest of course hairs present on the hind legs. The exact and complete use of the floral oils remains a bit of a mystery. Some ground-nesting Centris bees in tropical rainforests are thought to use these oils to waterproof the inside of their subterranean brood galleries. However, Centris nitida nests in cavities in trees and these energy rich oils may be incorporated into the protein rich pollen cakes mother bees prepare for their developing brood.

Watch at full speed and slow-motion as Centris nitida strokes the blossom to gather floral oils.

Centris nitida employs another interesting trick to gather food for her babes. Some plants have specialized anthers that only release pollen when properly shaken by clever pollinators. These plants include some of my favorites in the tomato family such as chilies, eggplants, and potatoes. Many bees, including Centris, grasp the blossom and vibrate their flight muscles to dislodge pollen from the anthers in the pollen-gathering behavior known as buzz-pollination.

The arrival of any nonnative creature in a new land is often cause for concern. In the case of Centris nitida, there is hope that it may help rare native Floridian Centris bees pollinate an endangered native oil-producing plant, Byrsonima lucida, which in turn is the host plant for larvae of the Florida Duskywing butterfly. Byrsonima lucida also produces fruit that are a source of nutrients for many birds. If chance or good fortune take you to central or southern Florida, try to catch a glimpse of these interesting and striking pollinators.


Bug of the week thanks Paula Shrewsbury for her clever camera work and Sam Droege for identifying Centris nitida and sharing his wisdom on its curious behaviors. The wonderful reference “The Bees in Your Backyard” by Joseph S. Wilson and Olivia Messinger Carril was used as a reference for this episode. Selby Gardens in Sarasota is a spectacular location to enjoy wildlife and provided the backdrop for this episode.