IMPACT ON THE ENVIRONMENT

Carpenter bees sometimes become a nuisance outdoors when they fly very erratically (hover) around the heads of people, causing fear. Homeowners complain not only about the aggressive nature, but about the round holes bored into wood trim near eaves and gables of homes, facia boards, porch ceilings, outdoor wooden furniture, decks, railings, fence posts, telephone poles, siding, shingles, dead tree limbs and other weathered wood. Initial damage is minor, but new tunnels may be excavated and old ones enlarged, causing considerable wood damage. Also, the yellow, coarse sawdust from borings beneath their entry hole contain their waste materials, leaving unsightly stains.

IDENTIFICATION

Carpenter bees resemble bumble bees. They are large, 3/4 to 1 inch long, heavy-bodied, blue-black to black colored with a green or purplish metallic sheen. The thorax is covered with bright yellow, orange or white hairs and the abdomen, especially on the top side, is black, shiny and bare without hairs. It is the males, with white markings on their head, that fly around aggressively, but they are harmless since they lack a stinger. Females have black heads, are docile and rarely sting. They have a dense brush of hairs on the hind legs whereas bumble bees have large pollen baskets and numerous, yellow hairs on the abdomen. Larvae are saclike, white and legless with brown, globular heads that bear small mouthparts. The pupal stage is passed in a silent cocoon.

LIFE CYCLE AND HABITS

Both male and female carpenter bees overwinter as adults within their old nest tunnels. Adults emerge in the spring (April and early May) and mate. Females provision the tunnels or galleries with bee bread (mixture of pollen and regurgitated nectar), lay an egg on top of the mass and close the cell with chewed wood pulp. She excavates the gallery with her mandibles (mouthparts) at the rate of one inch in six days. The gallery has a clean-cut round entrance hole with sharp edges 3/8 to 1/2 inch wide (dime-sized) on the lateral wood surface. The gallery continues inward for one to two inches, then turns sharply at a 90 degree right angle running in the same direction as the wood grain for four to six inches or up to 10 feet long, if used by many bees. Damage from a pair of bees is slight, but if used by many bees over several years, damage can be extensive. Each female may have six to eight sealed brood cells in a linear row in one gallery as she backs outward. Larvae develop on the pollen/nectar food mass provided, with the life cycle completed in 30 to 40 days. New adults chew through the cell partitions and emerge in late August. They collect and store pollen in the existing galleries, return to the tunnels to hibernate and mate the following spring. The previous year's adults die. They are not social insects and there is one generation per year.

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