Did you know only three states have more native bees than Colorado? Over 950 species of native bees are at home here on the Front Range.
Like bumble bees, many of the natives are plagued with the same pests and diseases that challenge honey bees. Around 25% of our native bees are listed as endangered species. Out of those 260 species, 95% are solitary bees. People who want to support these native bees and increase the pollination in their gardens don't have to become beekeepers to see their fruit and veggie harvest improve. Below are a few species, besides honey bees, that are recognizable in our Colorado yards. Solitary bees, unlike honey bees, do not live in a social structure. Some solitary bees nest in natural and man-made cavities. They can easily be provided with nesting habitats.
Bumble Bees
Bumble bees are large, fuzzy, docile bees. In Colorado we count more than two dozen species as regular residents. We love bumble bees! Here are two of the many reasons they're so cool. First, they can thermo-regulate. Have you ever seen a bumble bee "shivering?" The bee is warming its flight muscles. This ability means that bumble bees can fly earlier and later in both the day and the season. Second, they pollinate using a special technique called "buzz pollination" or sonication. The flower is violently vibrated by the insect resulting in superior pollination. Some plants require this type of pollination; tomatoes, peppers, and blueberries, for example. In Colorado, bumble bees provide pollination for many of our high altitude plants.
Leafcutter Bees
Leafcutter bees are appropriately named as they cut leaves to make their nests. Have you noticed perfectly round dime-sized holes in your rose leaves or Virginia creeper? A leafcutter bee has visited you! Leafcutters cut the leaf with their mandibles and carry the leaf piece back to their nest. It takes several leaves to make a nest. The female provisions the nest with both pollen and nectar onto which she lays an egg. The larva hatch, feed on the nectar and pollen, and metamorphose into an adult-- all inside the leaf nest! The following year, the adults hatch and the process repeats itself. Leafcutter bees are fascinating to watch.
For those of you who are uncomfortable around bees, you'll be glad to know that leafcutter bees are non-aggressive. They do not defend their nests like honey bees do. They sting only if they are manipulated and usually they bite before they sting. The leafcutter sting is not as painful as a honey bee sting.
Mason Bees
Mason bees have earned their name. They are tube nesters but they construct and seal their nests with mud instead of leaf pieces. Most common is the orchard mason bee which is a terrific pollinator of spring fruit trees. It is short lived and spends its adult life within 100 yards of its home and food source. There are about 140 species of mason bees in North America. All of them are solitary bees. The males do not have a stinger, and the females will only sting if trapped or squeezed. This makes them an ideal neighbor for the home garden, since they pose little threat to gardeners.
Bees are important pollinators. Some are quite specialized and only pollinate specific crops. For example, squash bees only pollinate plants in the squash family. Honey bees are generalists and pollinate most plants. Data is lacking on most bee species but they are thought to be in decline for a variety of reasons-- overuse of pesticides, lack of food and decreased habitat. You can do a lot to mitigate these problems! Reduce or eliminate your pesticide use and increase your clean, safe forage (food) planting. Solitary bees also benefit from housing opportunities and are exceptionally gratifying in your garden. Build it and they will come!
Bee House Placement
Your bee house must be positioned in full sun, facing southeast or due south. Station it at least three feet off the ground with no vegetation obscuring the entrances to the tunnels. This is very important. Solitary bees are cold-blooded and rely on the sun's heat to get them going in the morning so sunny spots are imperative. Unlike bumble bees, they have no furry coat to keep them warm! If you site your bee house in the shade or hidden behind vegetation it is unlikely to be used. A bee house should be firmly fixed so it doesn't sway in the wind. This means no hanging from a branch or shepherd's hook.
Protecting Bee Houses from Winter Wet
You can remove the occupied (sealed) logs and tubes and keep them in a cold dry place during the winter. You would then replace them in the bee house in March. An unheated shed, porch, or carport will do. Winter wet-- Not cold-- is the enemy. Do not store in a warm place, they need to be cold but protected from precipitation during the winter. Persistent, wind-blown heavy rain can dissolve the mud walls of the cells. This can cause both wooden blocks and cardboard bee tubes to rot, and the young bee pupae will succumb to fungus diseases.
Beware of Birds
If you notice woodpeckers or other birds attacking the tunnels in their hunt for bee larvae, fix a piece of chicken wire across the front of the bee house. This keeps the birds away while not deterring the bees.