Where the Diggers Dig
The farm has a beautiful manmade lake where the Digger bees come once every year to the water’s edge. Hundreds and hundreds were here building nests when I was here. The terrain is on a high south-facing mound so the bees have a home that will not flood from the rains or the lake.
The bees are present in April and May and can fly in cooler temperatures than other pollinators. These bees go hand in hand with the flowering fruit trees. They are great little pollinators. Oddly, they are not common in large orchards, possibly because a commercial orchard has to keep weeds down so tills and sprays the rows of trees. Another reason is these bees do not fly long distance to forage and require a nest near their feeding tree.
Digger bees make up 60% of the bee population in New York State. Digger bees are ground nesting, solitary bees such as Andrena, Lasioglossum, and Melissodes. I believe my bee is an Andrena. They are a genus within a family of about 1300 to 1500 species.
They are very docile bees and will not sting unless trapped. The males cannot sting at all. I noticed one bee per hole constructing the nest.
They are here at the site for a very short time in Spring. They arrive just after the skunks get done digging here for grubs. The earth is soft, loose and mounded, apparently the right consistency for the bees.
They are not very big bees, a little less than 1/2 inch long. Parasitic insects may try to steal into the nests, the one most common is a cuckoo bee. They lay their eggs in the nest and their young hatch first to devour the digger bee larva, then eat the food stored by the digger bee.
They pop in and out of the holes, lining their brood cells with a wax-like secretion. When they complete the cells, the females collect pollen which they pack into the chamber, then lay the egg in the completed cell.
Here are the finished burrows.
I am not sure which is the better nest, but the bees like sandy soils with free open spaces. They prefer an area of no plants threatening to either overgrow the nest or destroy it by means of their roots. The area at the lake has no plants other than native weeds and grasses. The adult bees die shortly after laying the eggs, so this opens the nest up to parasitic bees.
For some bee ‘portraits’ and fun bee facts, see my post Buzz on Bees.