Bee

Bees are part of the INSECT order Hymenoptera and are characterized by branched hairs on the body, chewing mouthparts (sometimes modified for lapping or sucking), transparent wings with few veins, hind appendages that are often enlarged with stiff hairs for gathering pollen, and a crop (honey stomach) for carrying nectar. Almost all species are adapted for gathering nectar and pollen from blossoms, which is important for pollination in agriculture and in the wild.

The sting at the tip of the female's abdomen is connected to poison glands. It is a modified egg-laying organ, or ovipositor. The sting of a worker honeybee is well barbed and, when removed, usually tears the bee's body, causing death. The queen's sting is used only against other queens. The so-called "stingless bees" (tribe Meliponini of the family Apidae) of the tropics and subtropics have similar appendages, but resort to other means of colony defence, such as biting and applying irritant plant materials to their foes.

Bees are diverse. Of an estimated 40 000 species worldwide, about 1000 occur in Canada. The most familiar bee is the western honeybee (Apis mellifera), a native of Europe and Africa. Several races are used for BEEKEEPING. Other familiar bees are bumblebees (genus Bombus), now used extensively in greenhouse pollination (B. impatiens, in North America), and sweat bees (family Halictidae) that sometimes land on us to imbibe perspiration.

The most notorious of bees are the so-called "killer bees" (Apis mellifera spp). These are a hybrid race of African and European western honeybees that originated in Brazil in about 1955. They have spread widely in the American tropics and subtropics. They gain their name from their highly defensive behaviour and propensity to sting en masse intruders near their colonies. Their range will not likely include Canada because they are incapable of withstanding severe winters.

Social Structure

Social structures range from completely solitary, to a few (often related) individuals sharing nests, to annual and perennial sociality. Most bees are solitary. Females of solitary bees make their own nests (some in aggregations), lay eggs and provide provisions for their offspring unaided by workers. Only some 500 species are social, having communal nests, co-operative brood care and a caste system of the queen (fertile and egg-laying female), workers (sterile females) and drones (males).

In Canada, highly social bees are represented by bumblebees and the introduced honeybee. Sex is regulated by fertilization of the eggs: eggs that are fertilized by sperm as they are laid become female but those that remain unfertilized develop into drones. This type of sex determination is called haplo-diploidy because males remain haploid (with only half the number of chromosomes of the diploid females).

External secretions (pheromones), especially from the queen, regulate caste structure and behaviour. Pheromones are also used to mark trails to food sources, although honeybees also use their dance "language" to communicate direction and distance to forage or other resources.

Nesting

In Canada, most solitary bees excavate tunnels in soil where they construct nest cells. Leafcutter bees (family Megachilidae), kept extensively for alfalfa pollination, fashion cells from precisely shaped leaf pieces. Carpenter bees (genus Xylocopa) nest in holes drilled in dead wood. Some members of mining bees (genus Anthophora) fashion unique clay nest cells underground. Hoary squash bees (Peponapis pruinosa) have similar nests with cells lined with a thin waterproofing material. Females of all these species provision each cell with pollen and nectar, deposit an egg and leave offspring to develop independently.

Some sweat bees live in small family groups in communal nests. Mostly, only one female lays eggs and the other bees help in provisioning.

Bumblebees are primitively social bees with annual societies. Their nests comprise honey and pollen pots and brood chambers. The queen emerges in spring, finds a nesting site (often in mouse nests) to start a colony and is actively seen foraging for floral provisions. She incubates the first brood she produces in the spring, but as summer progresses workers take over the roles of foraging and incubating brood. Later, the queen lays eggs that are destined to become new queens and drones. Colonies usually contain fewer than a few hundred to a thousand individuals, depending on the species. The social structure of the colony breaks down as the new queens are mated and each one seeks an underground shelter (hibernacula) to spend the winter. Only these new and mated queens survive till the next year. In Canada, 42 free-nesting bumblebee species are found, several above the Arctic Circle.

The most widely studied social bee is the honeybee. The precise architecture of the hexagonal cells of the comb, the complex social behaviour of the colony, the honey and beeswax they provide, and their efficiency in pollination make honeybees among the most fascinating and useful insects of humans. The colonies are mostly highly populous, with tens of thousands of individual bees under the influence of a single queen. A colony's population fluctuates during the year, being highest in late spring and early summer when swarming is most likely to occur, and lowest in late winter. The colony is active all winter long, kept warm by the bees' own body heat. The brood requires a temperature of about 37ºC to develop properly. Swarming is the colony's way of reproducing. A mass of thousands of bees, with a queen, exits from the parent colony and finds a new home. The parent colony continues in the old home, often with a new queen.

Some bees have evolved into parasites of their relatives and have lost the ability to gather food and rear their own offspring, eg, cuckoo bees of genus Psithyrus, which are closely related to bumblebees. The Psithyrus queen seeks out an established bumblebee nest and either replaces or lives alongside its original queen. She lays eggs that the host workers rear, producing only reproductive queens and drones.

See also INSECT, BENEFICIAL.