The bright colours of many ladybirds are to warn potential predators of their distastefulness (aposematism). They exude a yellow substance (reflex blood) when attacked which is rich in toxic alkaloids. Despite this, ladybirds do have enemies.
Records needed of harlequin ladybirds affected by natural enemies
If you have records or photographs of harlequin ladybirds affected by any of the enemies below,
we would be very pleased to see them. Please email the harlequin survey
Some birds, such as swifts and swallows, which feed on the wing are immune
to the defensive chemicals of ladybirds. Ladybirds are also attacked and
eaten by some spiders, some of the larger predatory beetles and true bugs
(Hemiptera), and their eggs and larvae occasionally fall prey to other species
of ladybird and to lacewing larvae.
Parasitoid wasps and flies
Several species of wasp and true fly lay their eggs on or inside
ladybird larvae, pupae or adults. When the eggs hatch, the larvae of these
parasitoids feed inside their ladybird host, exiting when fully-fed to pupate
and emerge as adults outside the ladybird, which dies as a result. These
parasitoids include the wasp Dinocampus coccinellae (Braconidae) -
see picture, at least
one species of scuttle-fly (Phoridae), and a tachinid fly.
7-spot ladybird with cocoon of Dinocampus coccinellae wasp underneath it.
Some mite species affect ladybirds, including sexually transmitted mites in
the genus Coccipolipus, which cause sterility in some ladybirds.
The soil dwelling fungus Beauveria bassiana is pathogenic to some
ladybirds species. The fungus produces infective spores which germinate and then
penetrate through the insect cuticle. This fungus then proliferates within
the host until it has utilised all available host resources at which stage
it erupts back through the host cuticle and produces more infective spores.
Fungi in the genus Laboulbeniales also affect some ladybirds
Some female ladybirds (including harlequins) are infected
with a male-killing bacterium (Spiroplasma),
which kills male but not female embryos. This male-killing
causes an imbalance in population sex ratios in some
parts of Asia. Work is currently in progress to find
out whether any of the harlequins that have arrived
in Britain are infected with this sex ratio distorter.