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Master Naturalists: Carpenter bees in the garden

July 14, 2011 at 2:14 a.m.

Carpenter bees are big, up to 1-inch long, black and shiny. The bees  have overcome a limitation all bees have when trying to get nectar from long flowers:  They have short tongues.  On long flowers, they land inverted, go to the flowers' base, and use their large mandibles or jaws to cut a hole where the nectar is and feed - as this bee is doing on a Turks cap bloom.

By Paul and Mary Meredith

A novel thing happened in our native-plant garden area about two weeks ago. Numerous large, all-black bees appeared to be feeding on our blooming Turks cap plants. There are no bees that have tongues (proboscis) long enough to get to the nectar in the Turks cap's long, narrow red blooms.

Even Charles Darwin observed that "individual differences in the curvature or length of the proboscis ... might profit a bee or other insect, so that certain individuals would be able to obtain their food more quickly (from flowers) than others..." In the case of Turks cap, they are better adapted to hummingbirds as a food source and pollinator than any bee we knew about.

WHAT WAS GOING ON?

When in doubt, catch one and look at it. Upon examination, the 1-inch long bees had formidable mandibles or jaws that had to be used for cutting tough material, and the usual short tongue.

That was the clue to why the bees landed on a flower, ignored the opening, which they could not get a tongue into, then turned upside down, and appeared to feed.

We picked some flowers and found horizontal cuts at the base of the blooms. Using those big jaws, they were cutting directly into the base or corolla of the bloom, sticking their short tongues directly into nectar-producing area and feeding. While stomping around, they were picking up pollen and were probably depositing some on other blooms, pollinating.

WHAT ARE THEY?

We knew they were not bumble bees because ours were hairless and shiny black, rather than being covered - as bumble bees are - with patches of orange to yellow hair.

Checking further, we found they were in a group called xylocopa bees, meaning "woodcutters" in Greek.

Commonly, these large bees are called carpenter bees, and they can become a pest. As folks in entomology at Texas A&M indicate, carpenter nest tunnels are about -inch wide and can start on the end of wooden beams, or at right angles to a surface for to 1 inch before turning and following the wood grain.

Tunnels are clean-cut and may extend 6 to 8 inches. They prefer unfinished softwoods such as redwood, cypress, cedar and pine for making nests that they may reuse for years. They also nest in dead trees, stumps, and in damaged places on trees.

CAN THEY HARM US?

Not really. Males will buzz around nesting areas appearing to defend it. It's all bluff; they have no stinger.

Females do have stingers, but are docile; they might sting if you grabbed one in your hand. If you see them around the house, barn or a wood fence line, check for the distinctive entry hole.

You can fill the holes and paint the area to discourage them from returning although the damage they do is primarily cosmetic. They do not eat wood, and their grubs are fed nectar and pollen balls and do not tunnel themselves. So, watch for them feeding and enjoy the show.

Paul and Mary Meredith are master naturalists. Contact them at paulmary0211@sbcglobal.net.

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