By Tina Mitchell
Enjoy cantaloupe or watermelon? The crunch of a crisp apple? That avocado in your guacamole? You might want to thank a bee.
Super-pollinators of the flowering world, Colorado’s bees emerge, starting in April, from their hives or their nests underground, in hollow stems, or in tree cavities. More than 20,000 species of bees have been identified worldwide, inhabiting every continent except Antarctica. More than 4,000 species of bees live in the U.S. and Canada: Four times more than all the bird species, six times more than butterflies and 10 times more than mammals. With approximately 950 bee species, Colorado has the fifth greatest statewide bee diversity in the U.S.
Think of bees, and images likely arise of a queen bee surrounded by worker bees, a hive filled with honey and swarms of stinging insects. But those images reflect only one bee species – the non-native, highly social Western or European honey bee (Apis mellifera). No other insects link more directly to human interests. For example, they transform plant nectar into honey – once, the sweetest substance known to humans. Honey bees construct their hives out of beeswax, used in many everyday products such as lip balm, candles or moisturizers.
The best known group of native bees are the usually large, fuzzy bumble bees (genus Bomba). More than 250 bumble bee species have been documented worldwide, but fewer than 50 occur in North America; half (24 species) call Colorado home. Since they live in colonies with a queen and workers, bumble bees are among the few social bees native to North America. Bumble bees have longer mouthparts than do most other bees; they can utilize larger flowers with deep sources of nectar. Honey bees heat their hive all winter with their collective energy while living off stored honey. But a lone, fertile bumble bee queen overwinters in the ground or in a cavity, establishing her colony anew each spring. Typically the first bees seen in spring and the last bees flying in the fall, bumble bees generate heat internally by shivering. They uncouple their wings from their flight muscles and contract them without moving their wings, becoming significantly warmer than their surrounding environment. Thus, they can actively forage in temperatures too cold for other bees.
A bee’s primary defense typically is her stinger. (Since the stinger is a modified structure for laying eggs, only females sting.) For most bees, this stinger is strongly barbed: After stinging a thick-skinned creature (say, a human), the stinger stays in the skin, ripping off the venom sack in the bee’s abdomen and killing the bee. Bumble bees’ stingers have no barbs, though. These bees can sting multiple times although they rarely sting even once.
Solitary bees provide most of the world’s bee diversity, and Colorado proves no exception (900+ native species). Each female constructs her own nest – no colonies here – and stocks it with nectar and pollen for her young. Generally docile, most solitary bees rarely sting. Since they don’t defend a hive filled with honey, such drastic, life-ending defenses don’t make sense.
Threats to bees abound, but impacts vary by species. A warming climate may affect honey bees sooner than bumble bees. In warmer temperatures, feeding activity of bumble bees increases; however, honey bee activity diminishes above 75 degrees. Expanding urbanization affects most wildlife, including bees. Yet native and honey bees can share many urban environments because each favors slightly different foraging opportunities. Bees are also vulnerable to pesticides and disease, again to differing degrees. For instance, field-based research results on neonicotinoids (a widespread, systemic pesticide) generally agree that bumble bees experience negative impacts, although the research of the impact on honey bees is more mixed. On the other hand, honey bees are susceptible to infestations by Varroa destructor mites, which not only directly kill the bees in the hive, but also introduce deadly viruses. Native bees tend not to be vulnerable.
Both native and non-native bees fill vital agricultural niches. Honey bees get most of the attention and indeed provide important pollination services for many, especially non-native, agricultural crops. But for millions of years, native bees have co-evolved with native flowering plants. These bees often provide more efficient pollination for native vegetables and fruits such as squash, cucumber, raspberries and blueberries – which honey bees don’t pollinate. Regardless, as Carol Ann Duffy wrote, “Bees are the batteries of the orchard, garden.” Cherish them, guard them, celebrate them.