REPRODUCTION
and
LIFE HISTORY
of
LADYBIRDS
 

All ladybirds are holometabolous. They undergo complete metamorphosis in which larvae (grubs) emerge from eggs (ova); the larvae eat, grow and eventually pupate; from the inactive pupa ("chrysalis") adult ladybirds (imagines) emerge.  European ladybirds overwinter as imagines.  The steps are similar for all sub-families of the Coccinellidae but the appearances of the stages vary considerably. The life-cycles of two tribes are illustrated here. There are further notes on other aspects of behaviour and life history.

Tribe Coccinellini (our larger, aphid-eating species)

British ladybirds over-winter as adults in relatively warm and dry places: cracks in bark, under leaf-litter, in garages or under window sills. They emerge in spring, and find a mate. Copulation may be prolonged (for days) as males try to exclude  rivals.		Yellow eggs are laid in sheltered places; sometimes in large clusters (such as the egg masses of the 7-spot) but sometimes in rows or singly. Often they are laid near aphids to provide food for emerging larvae.
After a week or so, small larvae emerge from the eggs. These eat voraciously (much more than adults do) and grow: they shed their skins as they pass through several stages (instars) (7-spot larva feeding on aphids on mugwort.)		After feeding, larvae attach themselves to some vegetation by their hind ends then contract into something of a dome shape. (This is a 7-spot pre-pupa.)
The pre-pupa hardens and becomes an inert pupa but, inside, its tissues are reorganising themselves - metamorphosis. Despite this, pupae have some powers of movement and may flick their free end at potential predators.		After a week or two, during which metamorphosis occurs within the pupa, an imago will emerge from the free end of the pupa.
Individuals which have just emerged have no pattern: they are mainly a weak yellowish colour which gradually darkens before the 'adult' pattern is clear. These are immature2-spots. 10-spots are much slower to gain their full colour		The remnants (exuvia) of the pupal coat remain attached to the plant surface and sometimes may be recognisable. This is from a 2-spot!

Tribe Chilocorini (our black, mainly scale-eating species)
 

Pine and kidney-spot ladybirds mate and lay eggs in the same way as their aphidophagous cousins. There larvae are grey-black, broader and flatter than coccinellines (above) with shorter legs.		They commonly attach to tree trunks: their pre-pupae are somewhat spiny (rather blurred pine ladybird)
Whereas the coccinelline pupae are formed by shrugging their larval skin to the base, chilocorines split their skins lengthways, forming a sort of boat shape. The newly exposed pupa is yellow in the pine (right) but distinctly red in the kidney-spot. It soon hardens		The pupa of the kidney-spot (right) is much spikier than that of the pine ladybird.

Variations amongst species
 

It is possible to recognise some species in their early life stages (although all eggs look much the same). There are keys for British larvae in their final instar (they can look very different in earlier stages). Pupae that have been infested by parasitoids take on a hyaline appearance with unusual patterns.

	Cream-spot ladybird The larvae are quite distinct with their creamy markings which increase in extent as the larva grows. It is quite a large animal in its final instar (right). A good example of the changes of pattern through larval growth: early and final instars may be very different.
	Cream-spot pupae also are distinctively marked. They are commonly found in cracks of bark.
	Eyed ladybird This tree dweller is also distinctively marked with white patches. (No pictures yet but that to the right is of the evacuated exuvium)
	Striped ladybird Photograph of larva by courtesy of David Element
	Orange ladybird This is most distinctive in all stages (larvae left, pre-pupa right, pupa below left) although the larva might be superficially confused with those of the yellow species.
	22-spot ladybird This larva is truly yellow with shorter legs than the Orange larva.
	Mealybug slayer Cryptolaemus montrouzieri Photograph of Australian larva by Peter Chew Very different from typical London ladybirds!
	Multivariate, harlequin, Japanese ladybird Is well illustrated on other pages. The only possible confusion is with its sibling the cream-streaked ladybird and with the eyed ladybird, neither of which are likely to be present in any number on urban plants.

Other aspects of life history
Over-wintering and other behaviour

All ladybirds overwinter as adults (imagines) although the Orange ladybird may survive as pupae. They choose sites which offer shelter from cold and, especially, wet. In nature this may be in leaf litter or under hedges: suitable sites may contain hundreds of ladybirds, often of more than one species. Ladybirds of coniferous trees may huddle down amongst needles in the canopy. The Pine and Kidney-spot ladybirds may take minimal shelter in the cracks of barks on the southern or eastern sides of tree trunks.
Many species seek shelter in human constructions: garden sheds, nesting boxes or Leylandii hedges. Many will enter houses and attempt to overwinter in cold bedrooms or garages; the 2-spot and (especially in east Essex) 11-spot may do this in large numbers. NOTE: if you find any in a heated room, it would be better to put them outside in a sheltered position - most die from lack of food, desiccation or over-heating.

Aggregation

Over-wintering aggregation is common for many species, especially the 7-spot. It often occurs in the same place year-after-year suggesting release of a long-lasting pheromone.
Pre- and post-wintering aggregation is common, often massive with the 16-spot and Orange ladybirds. 16-spots mass on fences, gate-posts, hedges in the autumn for no obvious reason, they are often on the northern or other exposed sides of the site. Oranges are often seen in large numbers in March, especially on the undersides of branches and sunny sides of trunks.
Spring-summer aggregations are less common and usually smaller. These are probably coincidental: ladybirds trying to avoid the cold (at night) or daytime heat (in Summer) may have limited options.

	16-spot ladybirds are seen in  large aggregations in autumn. They often accumulate on the northern sides of fences etc. so the behaviour is not to avoid cold. Photograph © Ian Menzies		However, even on warm days in the spring, they are often seen together in small groups.
	Orange ladybirds form large aggregations both before and after winter. In Epping Forest they have hibernated in beech mast on the ground.		Many ladybirds aggregate in growing tips of tree branches where aphids are feeding on new growth. Some stay amongst the leaves of evergreens through the winter. There were many 7-spots around the tips of an Araucaria (monkey puzzle) tree at Hodsock.
	Pine and Kidney-spot ladybirds seek minimal shelter even during the hardest of winters. Some merely using the shelter of bark crevices on the sunnier sides of trees.		In summer, ladybirds  'disappear' if the sky clouds over or rain falls, sheltering under foliage. They seek better shelter during cold nights, sometimes in unexpected places. This Kidney-spot sheltered under the knots of barbed wire. Other Kidney-spots and a 7-spot were doing the same thing along wire.

Death and disease

LINKS


RE-CREATED 29/9/2005