The reproduction and life history of ladybirds

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 as males try to exclude their rivals. Eggs are laid in sheltered places. Sometimes these are laid in large clusters (such as the yellow egg masses of the 7-spot) but sometimes in rows or singly.
After a few weeks, small larvae emerge from the eggs. These eat voraciously (much more than adults do) and grow. This is a 7-spot larva feeding on aphids on mugwort. Larvae of the various species of ladybird are usually fairly distinct. This is (probably) a Pine (the Kidney-spot has a similar structure).
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, their tissues are reorganising themselves - metamorphosis.
The pupae of Pine and Kidney-spot ladybirds differ in pupal formation: the dried 'skin' of the larva splits longitudinally to encase the metamorphosing pupa.. When the kidney-spot first splits, the inside is bright red. After some weeks, during which metamorphosis occurs within the pupa, an imago will emerge.
The remnants (exuvia) of the pupal coat remain attached to the plant surface and sometimes may be recognisable. This is from a 2-spot! 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

Pupae are unable to escape from predators and have little in the way of defence mechanisms. They are often eaten by bugs or spiders. This specimen has a hole which is too small for ladybird emergence and was possibly caused by insertion of the mouthparts of a bug. Parasites often emerge from small holes in pupae. Of course, not all larvae or pupae complete their metamorphosis. This larva/pre-pupa has clearly failed to mature.

 

 

 

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Over-wintering and other behaviour

All ladybirds (coccinellids) 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, it would be better to put them outside in a shltered 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 very 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 th winter. There were many 7-spots around the tips of an Araucaria (monkey puzzle) tree.
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 will 'disappear' if the sky clouds over or rain falls, sheltering under foliage. They will 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.

 

 

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Last modified 16.ii.2004