|Solitary bees: There are several species of solitary bees most of which nest in the ground. You can tell solitary bees from yellow jackets in the ground by the entrance hole to their nests. Yellow jackets will generally have one hole that they use to come and go from. Solitary bees nest sites will have many holes (they look like worm holes). Some are gregarious nesters with 100s, sometimes 1000s, nesting in the same area of ground. One of the most common solitary bee in our area is the Mason bee. The Mason bee is a solitary bee that can have large populations nesting together. They are all good pollinators and should be left alone whenever possible. We have never seen a solitary bee that is aggressive. Following are some of the most common solitary bees we see in our area. |
|Mason bee: Osmia lignaria|
The mason bee is a metallic blue color. From a distance they will look black. In April and May the mason bee emerges from the pupa cell it has been in all winter. They will sit on the walls in the sun on warm days. Mason bees will nest in the ground, in the cracks between shingles, in the drain holes of prefab windows, and in holes in wood.
The mason bee gathers mud and forms a cell at the back end of the hole or straw. She will lay an egg in the cell and provide it with a nectar-pollen mix. She will then seal the cell with mud and make another cell. She will continue this until the hole is filled. She seals the end with mud. The eggs hatch into larvae and feed on the pollen-nectar ball. They spin into the pupa stage and become fully-developed mature bees by late summer. They stay in the pupa cell overwintering until next spring (April-May). They chew their way out and emerge to do it all over again. When they nest in the ground they dig holes down into the ground and make holes out to the side where they make the mud cells.
|People make nesting blocks for mason bees by drilling 1/4" - 3/8" holes 3" - 6" deep in blocks of wood and setting this on a covered wall and the mason bees nest in the holes. Some people put straws in cans and the mason bees will nest in the straws. Here straws have been placed in the holes in the wood block and the mason bees have nested in the straws. |
|Leafcutter bee: Megachile|
We have several types of leafcutter bees locally. The leafcutter bee uses pieces of leaves to form cells. In the cell she lays an egg. She places a ball of pollen nectar mix in the cell and seals the end with leaf pieces. She will usually make several of these one after the other filling the void. The egg hatches into a larva and grows to a certain size, then stays dormant as a larva in the cell until spring when the larva pupates and hatches in late May thru June and July.
The larger and more common leafcutter bee is Megachile rotundata. This species will sometimes nest in mason bee blocks. Filling the hole with leaf pieces making a cell, forming several cells in the hole just like the mason bee does. We have seen this species nest in cracks between boards on a house, under mason blocks on sandy soil and in an old railing that had some rotten, puffy wood in the center (see picture below).
| The photo to the left shows leafcutter cells that are inside an old rotten wood railing. The 2 leafcutter bees in the photo above left, hatched from the cells in the wood railing. |
Below is a leafcutter bee. You can see the hairs that are on it. The leafcutter bee carries pollen on the underside of its abdomen where you see the yellow hairs.
|There is a small leaf cutter bee that will use the old combs of polistes wasp to nest in. Here you can see the cells of the polistes nest filled with leaf pieces of the leafcutter.|