LADYBIRD DEATH AND DISEASE

As with all animals, death may come about from 'natural causes' including starvation, dehydration and freezing.
Ladybirds suffer from predation, parasitisation and pathogens (bacteria, viruses and fungi).


NATURAL DEATH
 

Ladybirds live for about one year, usually less. Mortality occurs at all ages from predation and disease (below) but also from environmental effects: too cold, too hot,  too wet or too dry!  If a ladybird survives from from the egg to sexual maturation then it will probably die shortly after mating.  However, in "good" years, where there is plenty of food available and the winter has not been too harsh, it may survive until after the 'birth' of the new generation. This overlapping of generations is most common in urban areas such as London
 

PREDATION

Ladybirds, from the egg on, are likely to be eaten by many other animals from smaller beetles, spiders and bugs to large birds, herpetofauna and mammals.  Ladybirds do have defences: the adults of some species can secrete noxious fluids (reflex bleeding)  which deter predators. Pupae may twitch, often sufficiently to flick off attackers. 

However, in their early stages, a major source of mortality is cannibalism. Eggs, larvae and pupae are eaten by other ladybirds, including, or mainly,  their own species or siblings - cannibalism
 

	Anthocorid bugs (probably Anthocoris nemoralis) are commonly seen around ladybird pupae - probably some manage to penetrate the pupal defences. Photo © Les Wilson
	Ladybirds are often caught in spiders webs - they usually escape but occasionally don't (left).
	Ladybirds are often attacked by ants defending their flocks of aphids but they seldom seem to suffer serious harm.
	Mutual predators are often seen together - presumably aggression depends on how hungry one of them is? Ladybirds with bug nymph and (seven-legged) spider. (Photos Left © Denzil Devos; Right © Jill Attenborough)

PREDATION BY PARASITOIDS
[This is not true parasitism since the parasitoid almost inevitably kills its host.]

Dinocampus coccinellae The braconid wasp D. coccinellae injects its egg into adults of large ladybirds, especially the 7-spot. The eggs hatch into larvae which grow within the ladybird but do not kill it. They emerge and build a cocoon below the ladybird, attaching it to a leaf or trees trunk.		The larvae pupate here before emerging as full grown wasps.  The living-dead ladybird may act as a defence form other predators.
Other hymenopteran parasitoids are much smaller. The chalcid Aprostocetus neglectus injects eggs into the pupa (or earlier stage) of the smaller ladybirds, especially the Pine. These hatch, feed as larvae and emerge full grown from the pupa. They are very small and several may emerge from one pupa.		The chalcids (Chalcidoidea) are small hymenopteran (wasp) 'parasites' of insects and plants - there are a lot of them! There is undoubtedly scope to uncover more parasitoids of British ladybirds and other beetles.
Some parasitoids are flies, Diptera.  Most common are some species of phorid (scuttleflies) such as Phalacrotophora fasciata. These lay their eggs into larvae or pupae. Full grown larvae emerge and pupate rapidly (right). Small flies emerge after a few weeks.		They are particularly significant for Adalia species and the cream-spot ladybird, Calvia quattuordecimguttata. .
Parasitoids are often themselves attacked by others (hyperparasitoids). This happens with ladybirds but a good example is the large white butterfly larvae (right) which was attached to rosemary leaves by Cotesia glomerata - the cylindrical objects are Cotesia pupae.		[The caterpillar is still alive. ] These pupae were themselves later attacked by a small wasp, possibly Lysibia nanus, injecting eggs into the pupae. (click  for close up)

INFECTIONS AND TRUE PARASITES

To follow
 

CANNIBALISM
 

Cannibalism, eating members of the same species, is a common phenomenon in the animal world.
It is particularly obvious amongst ladybirds because these are easily observed but happens amongst many other predatory insects. In fact, it is not uncommon amongst vertebrates: in the absence of other food young tadpoles will eat their younger siblings. This may seem distasteful to humans but is a mechanism for ensuring that at least some of the brood survive.

Egg predation This (not very good) picture shows a 2-spot larva lurking around an egg packet on a sycamore leaf. It ate the eggs within a few hours despite the presence nearby of aphids - the eggs provide a high protein-fat diet and the larva does not need to waste energy foraging. This is quite a well developed larva but even the tiniest ones, just emerged from their eggs, will eat other eggs surrounding them.
Predation of larvae This final instar Adalia larva is eating a Pine ladybird pre-pupa but would just as likely eat members of its own species.
Predation of pupae This Pine ladybird larva is attempting to break into a pupa of the same species. It seemed to be unsuccessful - the Pine pupa has a very tough coating.
Some species may be more inclined to cannibalism than others. The multivariate Japanese ladybird (harlequin) Harmonia axyridis seems particularly cannibalistic although it probably eats more of other species than its own (right eating a 2-spot pupa). This, of course, may be a consequence of its being such a heavy predator of 'normal' prey such as aphids.

LINKS:
A paper on cannibalism among 7-spots



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CREATED 29/7/2002
LAST AMENDED 25/10/2005