Wood Boring Bees
The carpenter bee ranks as an important pollinator of the flowering plants, particularly those with large open fragrant blooms. Diligently, if unwittingly, it gathers pollen grains from the male parts of blossoms and delivers them to the female parts of other blossoms (of the same species), triggering the process of fertilization and seed formation. As a reward, it wittingly takes pollen, nectars and oils that it uses to set a banquet table for its larvae. The carpenter bee contributes substantially to the annual showcase of wildflowers in our desert basins and mountain flanks. In the near future, it may enlist, at the behest of researchers and farmers, in more commercial enterprises.
What is a Carpenter Bee?
The carpenter bee, along with some 25,000 other named species of bees in the world, belongs to an order called “Hymenoptera,” which also includes wasps, hornets and ants. Several carpenter bee species (of the seven in the United States) occur in the Southwest. The mountain carpenter bee, for example, occurs across the western U. S., said Lane Greer, “Alternative Pollinators: Native Bees,” Appropriate Technology Transfer for Rural Areas Technical Note. The valley carpenter bee occurs in Arizona and California.
A robust insect roughly the size of a small pecan, the carpenter bee is the only really large bee in the Southwest that is metallic blue-black to black, according to Floyd Werner and Carl Olson, Insects of the Southwest. Typically, the carpenter bee has a bare, black, and polished-looking abdomen, or rear body segment, probably its most distinguishing feature. Its legs have dense, electrostatically charged hairs to which pollen adheres when the insect visits blossoms. In some species, the male has a yellow face, and the female, a black face, according to the Oklahoma Cooperative Extension Service Internet site. The male valley carpenter bee has a tan-colored body, and the female, the usual black body, according to University of Arizona “Information Sheet 21” (Publication #196025).
In the desert, carpenter bee females nest in sotol and various yucca and agave bloom stalks, or they may take up residence in dead tree trunks and limbs, firewood or wooden structures. Beginning in the spring, a female, like a miniature carpenter, will burrow a half-inch-diameter horizontal tunnel so perfectly circular that it could have been produced by a power drill. She leaves, in her wake, a small pile of sawdust beneath her construction site. Within her tunnel, which extends perhaps six to 10 inches deep into wood, she excavates a gallery where she deposits her eggs.
With a home constructed for her family, she “then visits local flowers to gather pollen and nectar,” said the University of Arizona. “The female rolls the pollen into a ball, and pushes it to the back of the tunnel where she lays an egg. She loosely plugs the end with sawdust chips and other materials, forming a chamber roughly one inch long. She then goes to acquire more pollen and repeats the process until the tunnel is filled with chambers full of growing bees.” Her work done, she leaves her gallery behind, her parental duties done. After five to seven weeks, the young bees burrow out of the tunnel, feeding on pollen balls, then emerging to take up their own lives.
Often a female carpenter bee will re-use tunnels and galleries, and “Sometimes several bees will use the same entrance hole, but each ‘family’ will have its own gallery...” according to Michael G. Waldvogel, “Unlike Their Busy cousins, These Bees are Boring,” North Carolina State news release. Since a female always maintains her own gallery, even if she shares a tunnel, the carpenter bee holds a place among the “solitary” bees, which account the vast majority of the world’s 25,000 bee species. (“Social” bees, for example, honeybees, account for the balance.)
In the spring, especially around nesting sites, the male carpenter bee may turn into a perfect showoff, careening and buzzing through the air and bumping clumsily into whatever gets in his way. He wants you to think that he’s aggressive and threatening—a bully. But he’s bluffing. He has no stinger.
The female, as you might expect, behaves with far more dignity and restraint. She wants you to think that she’s a lady. But if you intrude into her space, she may attack. She will not be bluffing. She does have a stinger. She can inflict a painful wound.
Carpenter Bee Damage
The damage done by carpenter bees to residence in a wooden structure is usually quite superficial. However, given enough time and enough seasons spent in the nest, the carpenter bee can chew a simple, but prolific tunnel & gallery network through a house's timbers. Therefore, it is important to exterminate carpenter bees that have infested your home.
In the Southwest, especially in the Sonoran Desert, the carpenter bee belongs to a large cast of bee brethren. There are “...perhaps as many as 1000 species of bees distributed within the Sonoran Desert bioregion,” says the Center for Sonoran Desert Studies web site. “Unlike most other groups of organisms, bees are most abundant in numbers of both species and individuals in deserts and savannahs, rather than in lowland rainforests. The region around Tucson, Arizona, is thought to host more kinds of bees than anywhere else in the world, with the possible exception of some deserts in Israel.” Moreover, the Center says, “Of the approximately 640 flower plant taxa growing in the Tucson Mountains near the Desert Museum, approximately 80 percent of these species have flowers adapted for and pollinated by bees.”
A sampling of the carpenter bee’s desert relatives includes various species of dwarf carpenter bees, bumblebees, sweat bees, cuckoo bees and honeybees.
The dwarf carpenter bee, perhaps a fifth the size of the closely related carpenter bee, ranges in color from black to blue to bluish green in color. The female excavates a nest in the pith of plant stems, laying each egg in an individual cell. Unlike the carpenter bee female, the dwarf carpenter bee female remains with her nest, protecting it until her progeny hatch and emerge.
The bumblebee, a social bee about as large as the solitary carpenter bee, has an abdomen covered, distinctively, with yellow and black hairs. The bumblebee female typically raises her brood in a small underground colony, housing her larvae in clumps of cells and feeding them with pollen and nectar.
The sweat bee, comparatively small and often emerald colored, buzzes around your face, drawn by your perspiration on a hot summer day. The female digs branching burrows in bare soil, laying her eggs at the ends of the branches and provisioning her young with balls of pollen and nectar.
The typically brownish cuckoo bee, about the size of a fly and shaped something like a wasp, lacks apparatus such as hairs or spines on its hind legs for collecting pollen. An uninvited guest, it lays its eggs in the nests of pollen-collecting bees, leaving its larvae to consume the host bee’s food stores and even the host bee’s larvae.
The honeybee, introduced from Europe, ranks as probably the best known of our bees because of its economic value. In addition to producing honey, the honeybee “provides an estimated $20 billion annually from pollination of 120 cultivated crops,” according to the Oklahoma Cooperative Extension Service web site (“Honey Bees, Bumble Bees, Carpenter bees, and Sweat Bees”). On its hind legs, the honeybee has distinctive structures called “pollen baskets,” which are recessed containers with retaining hairs along the edges.
The Business of Pollination
Through an acceleration of the process of pollination through time, the carpenter bee along with ancestral and modern members of the bee cast have played a monumental, but largely unheralded, part in the history of the earth’s plant kingdom, including modern agriculture crops. Bees’ evolution and spread, which began about 100 million years ago, scientists think, have been reflected in the worldwide fluorescence of flowering plants. (Before the bees, the conifers, which produce their seed in cones rather than flowers, dominated the plant community.)
The carpenter bee, with other bees native to the Southwestern deserts, may be poised to make additional contributions to the agricultural crops of our region. The honeybees, which our farmers have counted on for years to pollinate their fields, have been struck by a parasite called a “Varroa Mite,” which sucks body fluids both from larvae and adults, decimating hives within weeks. Additionally, “A mysterious illness is killing tens of thousands of honeybee colonies across the country...” said Genaro C. Armas, in the El Paso Times, February 12, 2007. Moreover, European honeybee hives have been invaded by the extremely aggressive Africanized honeybees – or “killer bees” – which have expanded from southern Texas across southern New Mexico, Arizona and southern California since 1990, according to the Oklahoma Cooperative Extension Service web site. In some areas, honeybees have become sick and mean, rendering them far less valuable as pollinators of our crops.
The carpenter bee and its native friends may have to assume bigger parts, which can prove critical because, as the Center for Sonoran Desert Studies says, “...at least 30 percent of our agricultural crops require bees to move pollen between flowers. Not only are we dependent upon these ‘forgotten pollinators’ for over a third of our food, but for other products as well. Cotton cloth is a product that eventually results from bee pollination, and so are many beverages and medicines made from other fruits and seeds.”
The Carpenter Bee as a Professional Pollinator
The carpenter bee appears to be one of the prime native bee candidates for taking a lead role in pollinating agricultural plants of the desert. Arizona’s carpenter bees, for instance, “...seem very hardy, surviving daytime temperatures in excess of 115 degrees F, low relative humidity, and little moisture,” said Sean Adams in “The Busiest of Bees – Pollen Bees,” Agricultural Research. “These bees could be kept over winter for use year after year, unlike some pollinators that are reared from eggs each spring.”
Quoted by Adams, entomologist Stephen L. Buchmann, who has investigated the effectiveness of the carpenter bee in pollinating plants such as tomatoes, eggplants and cranberries, said that it “performs buzz pollination by curling its body around the pollen-beating anthers...” The bee “flexes its powerful flight muscles so fast that they create sonic energy that causes pollen to shoot out of the tomato flower’s hollow anthers. So much pollen is released, it looks like a cloud—enough to pollinate the flower and stick to tiny hairs on the bees.”
The Sustainable Agriculture Research and Education, Western Region (WSARE), in its annual report for 2001, said that carpenter bees adapt readily to new surroundings, orienting themselves quickly. They can be moved easily to locations near farmers’ fields. WSARE researchers were “developing ways of rearing, housing and managing the carpenter bee... By creating habitat for carpenter bee houses, farmers can guarantee that their crops will be pollinated, resulting in bigger and better produce.” The carpenter bee, the researchers suggested, could be ready for “commercial pollination services” within a few years.
If the native carpenter bee can fulfill its potential for commercial pollination, farmers of the desert can attract the insect by placing untreated wood blocks or branches or agave or yucca bloom stalks to serve for nesting sites around the margins of their fields. They can also preserve some natural habitat, with plants that attract the bee. It is likely that the carpenter bee, with his partners in pollination, will repay the favors with interest, which can be measured in terms of increased crop yields and more magnificent desert wildflower blooms.
By Jay W. Sharp
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