Native bee colonies tend to be annual—they survive just one season, unlike multi-year colonies of nonnative honey bees. (In tropical and subtropical regions, however, colonies can live through the year.) Taking bumble bees as an example of a native social bee’s life cycle, an individual queen emerges in spring and, after locating a nest site, builds a cluster of brood chambers, lays eggs, and then tends the first generation of larvae. When the adult bees—all female—emerge four to five weeks later, these workers maintain and enlarge the nest, gather food, and tend the queen and subsequent generations of young.

In late summer, the queen lays a special batch of eggs that produce both males (from unfertilized eggs) and fertile females (from fertilized eggs). Once mature, the males and females mate, after which most of the colony dies. Only newly mated females—now queens—survive to establish new colonies the following spring. (Note that separate colonies launch their males and new queens at the same time to ensure genetic diversity from cross-breeding.)

Disappearing Bees

What threatens native bees? Threats include habitat loss leading to lack of flowers for the bees, and degradation of bee nesting sites in soil and stems due to development and landscaping practices. In addition, millions of pounds of pesticides are applied to farms, roadsides, parks, and yards each year, killing both bees (and other insects) and the plants they depend on. Sixty-two kinds of North American bees are considered “species of concern” because their populations are threatened.

Bee-ing Parasitic

Some bee species are parasitic and don’t build nests at all. These bees often lay eggs in the nests of other related species. Cuckoo bees parasitize solitary bees by laying eggs in their host’s brood chambers. Their larva kills the host bee’s egg or larva and then eats its food. Female bees that parasitize social bee species trick the colony into raising their young by either killing the colony’s existing queen or hiding in the nest until they acquire the colony’s distinctive smell and can move in alongside the existing queen without a fight.

Which Bees Are Stingers?

Only female bees sting: Their stinger is modified from their egg-laying tube. All bees on flowers are busy foraging and will not sting unless disturbed. If a honey bee colony is disturbed at the nest entrance, they may sting to defend themselves. Africanized bees, a form of nonnative honey bees, are the most aggressive.

Bees and Flowers: Partners for Life

Bees and many flowering plants have a tight relationship: Flowers provide bees’ food; bees pollinate the flowers, allowing the plants to reproduce. Adult bees live on sugar-laden flower nectar and gather fat- and protein-rich pollen to feed their young.

Bee feeding preferences vary. Short-tongued bees prefer open flowers such as sunflowers, asters, mallows, and cactus. Long-tongued bees can reach into deep flowers like lupines, columbines, and orchids. Short-tongued bees that are small enough to crawl all the way inside can also get nectar from these deep flowers.

Many bee species, including all social bees, are generalists, foraging from any open blossoms. Some species, such as squash bees, stick to flowers of just one family or group of species—in this case, squashes and pumpkins. A few, including the tiny Mojave bee, are extremely picky eaters and rely solely on one species of flower. All native bees display “flower constancy,” foraging efficiently by concentrating on one flower species during each foraging flight.

This tendency to stick with one type of flower is what makes native bees so important as pollinators. Since plants are rooted in place, they need help moving their pollen, the male sexual cells, from one plant to the next in order to fertilize their flowers and produce seeds, which are embryonic plants. (Some species can self-pollinate, but cross-pollination results in more abundant and more successful offspring.)

Most flowering plants rely on animal partners to carry their pollen from flower to flower, though some, including cone-bearing trees and grasses, use the wind. (These plants’ pollen causes most respiratory allergies.) To attract animal partners, plants produce bright-colored, easily visible blossoms, enticing fragrances, and nectar. Their pollen grains sport bumps and prickles that adhere to their partners’ bodies, aided by a static charge on the bees’ hairs.

Bees are the most important group of animal pollinators because they deliberately gather pollen. A female bee on a single foraging flight may visit thousands of flowers, in the process dusting each with pollen from other blossoms of the same species. Some help bees by signaling when a particular blossom has been pollinated: The petals change color or fold up.

Biologists consider native bees keystone species because so many other species depend on these insects. Without bees, native flowering plant populations decline, as do birds and other animals that eat bees. Without the plants, whole ecosystems fall apart: Animals and birds lose food and shelter and soil erodes, degrading water and air quality as well. When native bee populations are endangered, that’s a sign that ecosystems and the humans that depend on them are also in trouble.

People can help native bees by minimizing pesticide use, putting up and maintaining bee boxes and bundles, and landscaping with bees in mind to restore habitat in backyards, parks, golf courses, farms, and wild areas.

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