Everett
The roller coaster of temperatures continues and is on the upswing. With warming temperatures, the solitary bees will be making their annual appearance just a little bit later this year. Did you know the majority of bee species nest below ground with around 70% excavating their own nests? Did you also know nesting in the ground is the ancestral nesting behavior of all bees including honeybees? The bees that nest below ground are known as solitary bees; I have also called them mining bees.
Ground-dwelling solitary bees are often confused with yellow jackets wasps. Many species of small bees that create individual (solitary) burrows in the soil and are also important plant pollinators. These bees include members of the Andrenidae family with multiple species found in Ohio.
Members of the Colletidae family are also found in our state and include the cellophane or plasterer bees based on the interesting practice of the females lining their soil burrows with a cellophane-like substance. Even the Apidae family which includes honeybees, (Apis mellifera) has some members that burrow into the soil, they are known as “digger bees.”
The visual difference between bees and wasps is wasps lack hair on their bodies. Bees, however, have hair that are plumose. Plumose hairs are hair that are branched. The plumose hairs enable bees to trap pollen grains more effectively. Bees are well-covered by plumose body hairs. They also have thousands of unbranched hairs covering their body which are for sensory purposes.
These ground-dwelling native bee pollinators are typically 3/16 – 3/4 inches long, depending on the species, and may sport banded abdomens. Females dig individual burrows several inches deep into the soil. They prefer to nest in well-drained soil that is lightly exposed to sunlight. This includes areas in landscaping with sparse vegetation, such as openings created by weakened turfgrass.
Each burrow consists of a hole about the diameter of a wooden pencil surrounded by a mound of loose, excavated soil particles. The loose soil particles can disappear after a heavy rainfall leaving only the hole.
Ground-dwelling bees are known as solitary bees with no social structure. However, large numbers of females often locate their burrows near one another giving the appearance of an organized colony. The collective nesting behavior may be associated with maximizing the chances for the females to find and mate with the males. I never really had the chance to ask the bees if this is why they nest this way, it is just an assumption.
The females become receptive to mating after they provision their burrows with wads of pollen mixed with nectar to nourish their larvae. You can observe receptive females peering from their burrows. If you keep watching, you will observe one or more males clamoring around burrow entrances intent on getting acquainted with a female, which commonly leads to a mating scrum … at which point you should look away.
Mated females deposit multiple eggs in their burrows, and the resulting larvae feed and develop on the pollen and/or nectar banquet provided by the females. Winter is spent as pupae in the burrows with adults emerging in the spring to start a new round of bees.
Mining bees are important polylectic plant pollinators meaning they gather pollen from many different plants. They are particularly important for pollinating spring-blooming food crops including apples, cherries and blueberries.
Unfortunately, the low-level flight plans and the collective buzzing sound made by the males may be frightening. While the females are busily digging and provisioning their burrows, the pugnacious males cruise menacingly back and forth just above the soil chasing other males or possibly predators. It is all a ruse because the males lack stingers.
Solitary soil-burrowing bees are not aggressive. Stings from these bees do not pack much of a punch; their small stingers cannot penetrate far into the skin. Only the female bees have stingers or ovipositors. The primary purpose of the ovipositor is for egg laying.
Of course, large numbers of bees buzzing around at knee-height may trigger fear. This normally prompts the ill-advised efforts to eliminate these beneficial insects including applications of insecticides.
As a society we are all about saving honeybees. However, when it comes to solitary bees, we have developed a NIMBY (not in my backyard) attitude. This practice of applying insecticides should be strongly discouraged. Instead, cultivation practices aimed at thickening turfgrass and mulching garden beds, will convince the bees to burrow elsewhere.
Save the planet, save the bees.
