These tubes can be used by a number of species including
Mason Bees (Genus Osmia), Leafcutter Bees (Genus Megachile), and
Grass-carrying Wasps (Genus Isodontia). The bees are what we want,
but the wasps are okay too (they do some pollinating). These are all
solitary species that do not nest in colonies. In the wild, these species
typically nest in holes excavated by beetles or in plants that have hollow
stems – the nesting tubes are a substitute for these natural cavities.
Each female Mason and Leafcutter bees gather pollen and
place it in a ball at the back of a nesting tube before laying a single egg on
the ball of pollen. She then caps off that section of the tube with a
ball of mud (Mason Bees) or a circle cut from a leaf (Leafcutter Bees).
She then repeats this process until the entire tube is full. The
Leafcutter bee will also line the inside of the tube with sections of leaves
before collecting pollen. The larvae will develop inside the tubes,
eventually forming a pupae. They will typically not emerge as adults
until next year.
The Grass-carrying Wasp does not gather pollen although she
does eat some of it (along with nectar). Instead she stings crickets,
katydids and other insects to paralyze them before stuffing them into the
tube. She then lays a single egg – when the egg hatches, the larvae eat
the paralyzed insects. After laying an egg she seals up the chamber with
bits of grass and repeats this process until the entire tube is full.
One other insect that may be seen entering the tubes is a
type of bee known as a Cuckoo Bee (multiple genera). These bees are nest
parasites. They lay their eggs in the nests of other bees. Because
they do not provide for their own young they lack the pollen carrying
structures and hairs found on other bees. They look more like wasps than
bees. I did see what I though was a Cuckoo Bee leave a nest tube at one
point.
All of these species are very nonaggressive and will rarely
sting unless grabbed or stepped on.
This first picture is labeled to show what I could see in each tube.
A nesting bee pears out of a cardboard nesting tube at the Mt. Pleasant Discovery Museum |
One done and a lot more to go - A Mason Bee lines a nesting tube with mud at the Saginaw Chippewa Academy |
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