Current Issue

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

Welcome class of 2016: Large carpenter bees, Xylocopa virginica


The morning dew glistens on the hairs of the yellow-faced male carpenter bee on the left and on the black-faced female carpenter bee on the right.


With the return of students to schools and universities, late summer is a time to greet new arrivals not only to our institutes but also to our gardens. Now is the time to enjoy the appearance of a new cohort of carpenter bees flocking to autumn blooming plants. In a previous episode we learned of the wood-boring antics of large carpenter bees. This week we return to these marvelous native pollinators. Months ago busy female carpenter bees devoted weeks constructing galleries in wood, provisioning these galleries with pollen, and depositing eggs within. Intervening weeks were a time for young bee larvae to consume these morsels, complete their development, pupate, and eclose as adults: voilà, the class of 2016! Galleries used as nurseries throughout spring and summer will soon serve as hibernal refuges during the cold months of winter. For now though, during the warmth of late summer’s days, blossoms hum with a multitude of bees including carpenters and their lookalike cousins, the bumble bees.


A gorgeous newly emerged female large carpenter bee with her body cloaked with pollen searches horsemint for sips of nectar.

This large patch of spotted horsemint serves as a nocturnal roost for many carpenter bees.

With a little practice, carpenter bees can be distinguished from bumble bees. Large carpenter bees have relatively naked rumps whereas bumble bee butts are usually quite hairy. The head of the carpenter bee is about the width of the thorax, the body segment just behind the head. The head of a bumble bee is noticeably smaller than thorax. Industrious bumble bee workers return to their nest at dusk with the final loads of nectar and pollen to fatten-up any future queens that might still be developing in the nest. But unlike bumble bees, with the approach of nightfall large carpenter bees often remain behind on blossoms to snooze. With no nest to provision or hungry future royals to feed, it is no surprise to find sleepy carpenters resting on flowers in the early light of dewy autumn mornings. One of the favorite resting spots in my garden for carpenter bees is a patch of spotted horsemint. Members of the mint family are renowned for their ability to attract a variety of pollinating insects and also known for their medicinal qualities. Perhaps the lazy behavior of my carpenter bees is related not only to the nighttime chill that cools their bodies, but also to some soporific chemical found in the nectar of mint. When the killing frost finally puts an end to my autumn bloomers, the last of the lazy carpenter bees will enter the brood galleries, not to return until next spring. On a cool autumn morning take an early trip to the garden to visit the newly arrived class of carpenter bees.