Order: Hymenoptera
Family: Halictidae, Colletidae, Andrenidae, Melittidae, Megachilidae, Apidae


Bees are flying insects and are frequently observed visiting flowers throughout blooming periods in the spring and summer. Like all insects, bees have three pairs of legs, antennae, and three body segments called a head, thorax and abdomen. There is highly variable morphology among bee species; bumble bees have more rounded and robust bodies covered in dense patches of hair called setae, while sweat bees are smaller and slenderer with fewer setae. Bee coloration largely depends on species and can range from shades of yellow and black, to white and black, and even a lustrous green or blue. 

Quick Facts

  • In addition to ants and wasps, bees are social insects in the order Hymenoptera.
  • Bee populations are in decline due to a combination of human caused stressors including habitat loss, climate change, and pesticide exposure. Efforts are continuously in place to improve sustainability in agricultural pest management to minimize adverse impacts on pollinators.
  • In some bee species, a single beehive can reach sizes of up to 80,000 individuals. In large hives like these, all workers are female offspring from a single queen.
  • There are around 3,500 bee species in North America, with roughly 1,000 bee species found in Colorado. Worldwide, there are at least 20,000 described bee species.
golden northern bumble bee

Golden northern bumble bee (Bombus fervidus)
Ansel Oommen,

Bees are important pollinators in agricultural systems. Much of an adult bee’s life is spent foraging for nectar and pollen. The tiny hairs on their body and legs make them very good at picking up and transferring pollen as they visit flowers on different plants. This transfer of pollen from one plant to another is known as cross-pollination and is necessary for viable seed production in many plant species.

sweat bee

Sweat bee (Agapostemon sp.) foraging
David Cappaert, Environmental Sciences Magnet School (Hartford CT),

dirt wasp nest

Nest constructed with soil.
Chelsey Ritner, Exotic Bee ID, USDA APHIS PPQ,

carpenter bee

Carpenter bee in its nest (Xylocopa sp.
David L. Clement, University of Maryland,


A single beehive. Bumble bees, honey bees, and stingless bees form hives with a caste system.
Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo,

Life History and Habits

  • All bees undergo complete metamorphosis, meaning they have four life stages: egg, larva, pupa, and adult.
  • Bees utilize a variety of nesting strategies. Some bees live in solitude, with each female establishing a single nest, while other species establish a communal nest shared among several unrelated females. Honey bees establish a hive with a caste system where all worker bees are the daughters of a single queen. Some bees are parasitic and invade the nest of other species where they steal pollen and honey to nourish their young.
  • Nests can be established using a variety of building materials and locations. Some bees nest by digging in soil, while others establish nests in plant stems or tree hollows.
  • The number of generations produced each year is species-specific. Bees living in hives produce multiple generations per year, while some solitary bees produce a single generation each year.
  • Pollen specialization varies among bee species as well: females can gather pollen from only a few related species or genera from a single plant family (oligolectic), from plants in a few plant families (mesolectic), or from many different plant families (polylectic).


Insecticide residues pose a major threat to bees. To reduce exposure, apiaries should be placed a minimum of four miles from any crops treated with pesticides. To help alleviate stress on wild bee populations, farmers should adopt sustainable measures when applying pesticides. Important considerations to make include the weather and time of day in which the insecticide is applied, the type of formulation, and pesticide toxicity and longevity.

Spraying on windy days should be avoided as this can cause pesticides to drift from the target area to an apiary or adjacent crops with foraging bees. Since foraging behaviors are restricted to daylight hours, spraying pesticides in the evening can substantially reduce exposure to bees. Pesticides also come in different formulations with different application methods. Some pesticides are sold as dusts and wettable powders; these should be avoided as they will readily adhere to the tiny hairs found on the surface of a bee’s body. When possible, pesticides with lower toxicity that degrade rapidly should be used.

In some instances, bee colonies can recover from pesticide exposure if enough honey and pollen reserves are available to support colony growth. However, pesticide contamination of honey and pollen reserves will prevent the colony from recovering since brood and nurse bees will continue dying. When this situation arises in honey bee hives, the combs should be removed or cleaned by soaking in water for 24 hours. After soaking, combs should be cleaned of any pollen and allowed to dry. Another option is to completely remove the wax comb and replace it with new foundation.

cuckoo bee

Cuckoo bee (Coelioxys sp.)
Joseph Berger,


Michigan State University (n.d.). Pollination. Available
University of Georgia. (n.d.). Bees, Beekeeping & Protecting Pollinators. Available