Page 85 - BBC Wildlife - August 2017 UK

7-SPOT LADYBIRDS

CAREFUL MOTHERS

Female 7-spot ladybirds lay their tiny yellow
ovoid eggs in clusters of about 20 near aphid
colonies. I find it remarkable that they assess
an aphid colony to ensure it’s not on the
point of collapse before choosing it. Too many
shed aphid husks and the female will move
on. She can even detect the presence of other
ladybird larvae in the vicinity through the chemicals
left behind in their footprints. Since these larger larvae are
likely to eat her eggs or newly hatching larvae, she will again
move on until she finds a more suitable location.

The characteristic red coloration of the 7-spot is not
yet apparent; instead, an adult emerges a translucent
yellow colour. I still enjoy watching the colour develop
as the pigment is laid down. The first hint of the black
spots begin to appear within hours, then slowly the
yellow turns to orange, finally deepening to a bright red.
Utterly magical. During this transformation, a ladybird
is vulnerable to attack by predators, particularly other Top left: mated because they lack sufficient energy reserves or because
females lay eggs
they are host to one of a number of amazing parasites.
arvae: Matt Co e: pupa: Genevieve Vallee/Alamy; are spent building up fat reserves to see it through the the eggs hatch charismatic as the ladybirds themselves. Over the years,
ladybirds, because it is still soft-bodied. But it rapidly
in June and
Here, I have to admit to finding ladybird parasites as
scuttles off to hunt for food.
July. Top right:
For an adult 7-spot ladybird, the summer months
I have tried to convince others of this and have largely
into distinctive
bristly orange
failed, though I have worked with many students who
coming hostile winter. The beetle will not breed, even
and black larvae.
have shared my passion and gone on to unravel the
if the weather seems favourable and food is plentiful,
Centre: the larva
because its reproductive system needs a cold period to
ecology of the ladybird underworld.
becomes a pupa.
mature. You can actually speed the process up by placing
Perhaps my favourite parasite is the small parasitic
Above: a fresh
braconid wasp, Dinocampus coccinellae. It lays a single egg
adult emerges
7-spot ladybirds in artificial winter conditions (putting
from its pupa.
them in a fridge for a few weeks), and in fact we often do
inside a ladybird, from which hatches a maggot. Not only
Predat on: Matt Co e; eggs: Chr st an Hutter/Imagebroker/FLPA; adult: James H. Robinson/Science Sour/ardea.com; stamp: Stan Pritchard/Alamy GOING TO GROUND it also has extremely sophisticated ways of feeding itself
this in the lab to ensure a continual supply of ladybirds.
does the growing parasite consume some of the beetle,
while keeping the host functioning almost normally.
When the maggot outgrows its ladybird home, it still has
As days shorten and temperatures fall, 7-spot ladybirds
begin to seek a suitable place to spend the winter.
a need for some protection. So it emerges, importantly
Nestling under leaf litter or crawling under fallen trees,
leaving the leg muscles of the ladybird intact.
The maggot heads underneath its host to spin a
the beetles opt for positions near the ground. By contrast,
cocoon, thereby sticking itself and the ladybird down.
2-spot ladybirds and other species choose elevated
The ladybird will twitch and shake over the developing
positions in trees or even houses. (The non-native
wasp, unwittingly acting as a very effective bodyguard.
harlequin ladybird, originally from Asia, is particularly
fond of wintering indoors in large aggregations, often in
each can lay about 200 eggs, so it not surprising that
tall buildings.) And so the ladybird year ends.
Many adult 7-spots will perish over the winter, either
about one in ten 7-spot ladybirds succumb.
85
BBC Wildlife
August 2017 Intriguingly, all of the adults of this wasp are female and