Osmia cornuta is
one of the first solitary bees to emerge in spring and as such is an important
pollinator of fruit trees such as apricots, plums and almonds. Present in most of Europe ,
(not the north), it is a species that has disappeared from most areas of
intensive agriculture, but it survives well in some urban areas, wastelands,
public parks and gardens in particular areas.
Given this living where we do in the intensive cereal lands
I was extremely pleased to see a group of these about midday buzzing around the table on the patio in the
sunshine. At first I thought they were Osmia
bicolor with their bright orange abdomens and black head and thorax, not
easy to see when they don’t settle. Anyway, a little later Lynne called me to say
that a couple were kindly putting on a performance for me on the table and providing a photo opportunity.
Please Click on images to enlarge.
They are closely related to both Osmia bicolor the Two Coloured Mason Bee and Osmia rufa, the Red
Mason Bee and they behave in much the same manner. The female builds a nest in
an elongated hole, often in an old branch or some other piece of timber. The
majority of the holes are between 5 to 8 mm in diameter and the nest is formed with
a series of cells separated by clay partitions. Each cell contains a food
reserve formed by a ball of pollen and nectar, on which an egg is laid. If the
gallery is too long, a dirt cap is raised by the female to reduce its size. As
a generalist pollen collector they will use what ever is available according to
season, this is taken to the nest and mixed with regurgitated nectar to make
the so called bee bread which is made into a pellet stuffed into the cavity. When the cell
is half full following 10 to 30 trips, the female lays an egg and builds a
front wall with some clay and then repeats this until the tunnel is full with up to
15 eggs and then seals the outside with a clay plug. She repeats this for about
two months building one nest after the other.
When the eggs hatch the one that were laid first which are
to be females develop more slowly. When fully grown the larva spins a light
brown thread cocoon and transforms into a pupa.
The bee is fully formed in late summer but remains where it
is until the following spring.
The mortality rate is very high; perhaps 60% or more never
get to fly and in part this is caused by Cocoxenus
indagator, is which a ‘fruit fly’ and a cleptoparasite of Osmia species that lays its own eggs in
the bees nest when the bee is away foraging. Having said that it’s built in to
the numbers of eggs produced so nothing to be concerned about as long as the
habitat requirements are met.
Places used for nests include - Hollow stems; Galleries in
walls, soft stones or soil; Gaps in window frames and drainage holes; Old
galleries dug by other species of Hymenoptera; Natural or artificial galleries
in timber with holes of a diameter of 8 to 10 mm; Sometimes even snail shells
as with Osmia Bicolor. Galleries are thoroughly
cleaned before any eggs are laid and can be used almost indefinitely. All of
these locations are available at our place and with no chemicals or poisons
they should go on to thrive.
Definitely one to look out for in France.
Chris
