|
Probably more bumblebees are
killed by parasites (see right) than by predators. This may be because the bumblebee
females are armed with a sting, but it is also due to the protection given by
their warning colouration.
Some crab spiders
ambush bumblebees at flowers, and a few species of bird can remove the sting
before eating the bumblebee, e.g. bee-eaters, spotted flycatchers
and shrikes. In the U. S.
there are wasps called beewolves in the genus Philanthus, these wasps specialise in hunting bumblebees. The
bumblebee is caught while feeding and is paralysed with a sting, it is taken
back to the nest and enclosed with a wasp egg in a cell, there are usually
about five bumblebees in each cell.
Other predators are small mammals, badgers, foxes, and minks, and in the US skunks and bears. All break open and destroy nests to eat the larvae, bees and food stores, but
there are no vertebrate predators that specialise in bumblebees.
|
Cuckoo
bumblebees, Psithyrus spp. Cuckoo females enter the
bumblebee nest and lay their eggs, the bumblebee workers then rear these eggs
as if they were their own sisters and brothers. These bumblebees have no
pollen baskets on their rearmost legs, and
do not secrete wax for nest construction. There
is no worker caste, and all cuckoo bumblebee eggs hatch as reproductive males
or females.
Wax moth, Aphomia
sociella. The adult moth enters the bumblebee nest and lays her eggs,
at first the caterpillars feed on nest debris, but as they grow they switch to
feeding on the wax food cells, food stores and even larvae. Normally this
destroys the nest. The moth leaves the nest to overwinter as a pupa in a
sheltered spot. In the UK bumblebee boxes have become popular in recent years. If your box is invaded by the wax moth than I'm afraid there is little you can do for the nest as by the time you have discovered it it is too late. All you can do is clear out the nest contents and get it ready for the next year. Invasion of the nest by the north American wax moth
Vitula edmandsii does not always lead to the destruction of the
nest as it does not feed on the larvae.
Brachycoma
devia is a fly that look a little like the common house fly. The female
enters the bumblebee nest and lays larvae (this fly does not lay eggs) among
the bumblebee larvae. The fly larvae attach themselves to a bumblebee larvae
and wait. Once the bumblebee larva has spun its cocoon the fly larvae start
feeding on it and suck it dry. When they are fully grown they (one bumblebee
cocoon can support 4 parasitic larvae) leave the bumblebee cocoon and pupate in
the bumblebee nest. A heavy infestation will lead to the death of a colony.
Conopid flies. The
female fly waits on flowers till a bumblebee comes to feed, then she jumps on
the bee and quickly pierces the bee's body laying her egg inside. The egg
hatches inside the bee and feeds off its abdominal contents till it more or
less fills the entire abdomen. The bumblebee dies after about 10 days and the
fly larva pupates inside the husk of the dead bumblebee body emerging as an
adult fly next summer. This parasite can change the behaviour of the bumblebee.
Infected workers tend to stay outside the nest more than other workers, often
remaining out all night, and they tend to favour colder microclimates, also
before the bumblebee dies it attempts to bury itself.
Mites. Locustacarus buchneri lives in the air sacs of the bee where it feeds on the haemolymph. It will not kill a colony, but it will weaken one. The mites hibernate inside new queens. |
