A native bee is a bee that occurs naturally in a region. Colorado has over 950 species of bees, and all but a handful of these are native. Most of the few introduced (i.e. non-native) species that now call Colorado home were brought in accidentally. The most well-known non-native bee is the honey bee. Honey bees were intentionally brought to North America. Today, honey bees are important pollinators of many of our agricultural crops, especially those that are also non-native. But our native bees, who for millions of years have co-evolved with our native flowering plants, are much more important, efficient, and effective pollinators for native fruits and vegetables. Many of these, like squash, tomatoes, and eggplants, cannot be pollinated by honey bees at all!
Colorado has the 5th most bee diversity of any state in the US. Colorado is home to some 950 bee species that range dramatically in color (black, brown, grey, blue, green, red, orange, and yellow), shape (round, oval, elongate, and even triangular), hairiness (almost bald to completely fuzzy), and size (smaller than a gnat to over an inch). They also behave in very different ways. A comprehensive list of Colorado bee species is reported in The Bees of Colorado.
When you think about bees, you probably envision a swarm of black and yellow insects busily buzzing around a hive. Not only are most of Colorado’s bees not black and yellow, only about 12% of Colorado’s bee species are social. A social insect lives in a colony with a queen, worker and drone (male) “castes”. In Colorado, these social bees include the introduced honey bee, 20 species of bumble bees, and many of our sweat bees. The majority of bee species in Colorado, about 70%, are solitary with each female constructing and provisioning her own nest, much like a bird does. These include the plasterer bees, masked bees, mining bees, digger bees, mason bees, resin bees, leafcutting bees, and some sweat bees. The remaining 18% of Colorado’s bee species are parasitic on other bees. These include social parasites and cleptoparasites. Social parasites, including 4 species of bumble bees and some sweat bees, sneak into the colonies of other closely related (social) species and take over: replacing the queen and laying her own eggs. Cleptoparasites sneak into the nests of other solitary bee species and lay an egg, which will hatch and the cleptoparasitic bee offspring will feed on the food stored for the host bee larva. These species are called cuckoo bees because their behavior resembles that of the cuckoo bird.
Like butterflies, all bees go through complete metamorphosis and have four life stages: egg, larva, pupa, and adult. Unlike butterflies which merely lay eggs on acceptable host plants, bees build nests and provision "cells" (i.e. rooms or chambers) filled with pollen and nectar as food for their offspring. Bees are “sexually dimorphic”, which means female bees may look very different from males of the same species (think about hens and roosters--they're sexually dimorphic, too!). The life span of an adult bee may vary from only several weeks to years in the case of a queen honey bee. Our solitary bee species survive the winter still in the nest they developed in, usually in the larval stage, with the previous year’s adults all dying with the arrival of freezing temperatures in the Fall.
Most of our Colorado bee species nest in the ground, although these nests are easily overlooked. Occasionally, you may notice a large collection of digger bees along a trailhead, but for the most part, it can be very difficult to find ground nesting bee nests (plasterer bees, mining bees, sweat bees). The other place that bees typically nest is in wood. While a few species including our small carpenter bees will excavate their own nesting tunnels, many species nest in pre-formed cavities. Small cavities including burrows made by beetle larvae in wood or the pithy center of small twigs like roses or brambles provide nesting sites for about one third of Colorado bee species (masked bees, mason bees, leafcutting bees, and). Just like chickadees and bluebirds use nests excavated originally by woodpeckers, these bees rely on beetles and other animals to make their nests for them, or they use nooks and crannies that just happen to be there. The bees that nest in these small cavities add nesting materials to their tunnels: leaves, mud, plant fuzz, resin… When their nest is completed, they plug the tunnel entrance. Different types of bees use different materials and we can tell who nested in the tunnel by what materials were used. For more information about where bees nest read this informative and beautiful publication by the USDA.
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