Probably more bumblebees are
killed by parasites (see below) 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. These spiders do not spin webs, but sit and wait for their prey to come within reach. They are well camouflaged. In north America Misumenia vatia catches bumblebees as they land on flowers.
Robber flies catch their prey on the wing in their legs. And in north America have been found to prey on bumblebees.
A few species of bird can remove the sting
before eating the bumblebee, e.g. bee-eaters, spotted flycatchers, tits and shrikes. The Bombus lucorum queen on the left was probably killed by a bird. They rub the sting off before eating the abdominal contents which would include the honeystomach.
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.
Predation of foraging bumblebees -almost the only time when humans see them is relatively rare. All of the above are predators of foraging bumblebees.
Other predators break into nests and include badgers, who will eat the entire brood, wax, stored food and any adult bees that do not escape. In north America skunks do the same. Foxes, minks, weasels, bears, field mice and shrews are also predators. In Iceland the mink is the major predator. However there is no mammal that specialises in bumblebee predation. More recently I've been hearing of hedgehogs which break into bumblebee nests that are above ground and not in solid structures. Like badgers hedgehogs would relish the grubs and any stores of honey and pollen.
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
Wax moth, Aphomia
sociella. In northern Europe the wax moth is regarded as the most serious enemy of the bumblebee, and is found only in bumblebee nests. In some areas in southern England as many as 80% of nests can be destroyed. The adult moth flies from June - August. It 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, It spins a strong, brown cocoon in autumn. 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 in Europe and Brachicoma (Brachycoma) sarcophagina in north America are flies that look a little like the common house fly. The female
fly 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 larva
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.