It’s like an Alfred Hitchcock
movie. Or maybe like the
Biblical plagues of Egypt. And
it happens every year around the
end of December or beginning of
January. Swarms of alien ladybirds
reach high-lying homes in Zwavelpoort
and Mooikloof.
These ‘goggas’ can by no means
be described as ‘ladies’. They push
through cracks in windows and
creep through crevices and air
vents just to get inside. Once inside
they form tight clusters in corners,
behind ornaments, books and
furniture and try their best to hibernate
there for the rest of the season.
When disturbed, they cause
smelly yellow stains that are difficult
to get rid of.
Ladybirds annually invade high-lying homes in Zwavelpoort and Mooikloof
Why on earth they try to hibernate
in mid-summer, and where they
come from, nobody seems to
know. How long they’ve been
doing this in our area is also not
clear – people estimate it to be
about a decade.
Reports indicate infestations in
houses on the Bronberg ridge and
those on hilltops in Mooikloof, but
high-lying houses in Olympus
apparently don’t fall prey to these
invasions. The orange ladybirds
seem to migrate in a narrow band
and always fly north from a
southerly direction.
Those attempting to identify these
ladybirds have come to the conclusion
that they cannot be indigenous
because they seem to have
no natural enemies here. Available
information has led us to suspect
that we are dealing with the Asian
ladybird.
Entomologists are welcome to disagree
with us and are invited to
send us more information. We’ve
determined that other ladybird
species, such as Hippodamia convergens,
also gather into groups
and move to higher land, such as a
mountain, to hibernate. However,
this species has a black head, a
feature lacking in our local home
invader.
Swarms of ladybirds reach Zwavelpoort?s Bronberg ridge each year |
These ladybirds force blood out through their joints,
resulting in a yellow stain that is difficult to get rid of |
Pest
Our leading suspect, the Asian
ladybird, Harmonia axyridis, was
introduced to the rest of the world
as a biological control agent
against aphid and cale infestations
in greenhouses, crops and gardens.
They can quickly disperse over
long distances and so have the
potential for rapid geographic
expansion. These ladybirds are
increasing internationally to the
detriment of indigenous species.
They have a voracious appetite
which enables them to out-compete
and even eat other ladybirds
and larvae. Native ladybird species
have experienced dramatic declines
in areas invaded by these
foreigners.
In Britain, 46 native ladybird species
are under threat. Introduced
from Asia into North America to
control plant pests, they have
spread across all states, becoming
by far the most common ladybird
in less than 20 years.
In Europe they got the name‘harlequin’ because of the species’
tendency to vary in colour from a
deep orange to yellow. The harlequin
measures between 5-8 mm,
but can be difficult to identify
because of the variations in colour,
spot size, and spot count.
Bleed
Harlequin ladybirds cause stains
because they can force blood out
through joints and other weak
areas in their exoskeleton, an adaptation
called ‘reflex bleeding’. Like
other ladybirds, their blood contains
isopropyl methoxy pyrazine
which they use as a defensive
chemical to deter predation.
But these invaders contain this
chemical in its haemolymph at
much higher concentrations than
many other ladybird species. That
is why the reflex bleeding has such
a foul odour.
It is believed that some people
have allergic reactions when repeatedly exposed to these ladybirds
which, apparently, can also
bite.
Harlequin ladybirds hibernate in
cooler months, although they will
wake up and move around whenever
the temperature reaches
about 10°C. Because they use
crevices and other cool, dry, confined
spaces to hibernate, significant
numbers may congregate
inside homes. These large populations
can be problematic because
they form swarms and linger in an
area for a long time.
Luck
Before the invasion of the harlequin,
ladybirds and their larvae
have always been considered as a
bonus to any garden. Some people
consider seeing them or having
them land on one’s body to be a
sign of good luck, and that killing
them foreshadows bad luck.
In parts of northern Europe, tradition
says that your wish will be
granted if a ladybird lands on you.
In Italy, it is considered good luck
if a ladybird flies into your bedroom.
In central Europe, a ladybird
crawling across a girl’s hand is
thought to mean she will get married
within the year.
In Russia, there is a popular children’s
rhyme where a ladybird is
asked to fly to the sky and bring
back bread. Similarly, in Denmark
children ask a ladybird to fly to“our Lord in heaven and ask for
fairer weather in the morning”. In
Irish, the insect is called “God’s little
cow”.
The esteem with which these
insects are regarded has roots in
ancient beliefs. Despite the fact
that their blood contains toxic alkaloids
- or perhaps because of it –
ladybirds have been used for
medicinal purposes. People in pre-
Industrial Europe used ladybirds as
a cure for measles and colic. They
were also mashed and stuffed in
cavities to cure toothaches.
A closer view of the intruders
Family
Ladybirds’ family name comes
from their type genus, Coccinella.
Coccinellids are found worldwide,
with over 5 000 species.
Most ladybirds mate in spring or
summer and the female lays a cluster
of eggs, numbering from a few
to a few hundred, depending on
the species, as near as possible to
an aphid colony.
They also lay extra infertile eggs to
provide a backup food source for
the larvae when they hatch. The
ratio of infertile to fertile eggs
increases with scarcity of food at
the time of egg laying.
Ladybirds develop rapidly. The
larva emerges from the egg five to
ten days after being laid and reaches
maturity within two weeks.
Pupation takes place on the plant
where the larva fed and the adult
emerges from the pupa after four
to ten days. There are eight indigenous
Coccinelidae subfamilies in
southern Africa.
Ladybirds are often brightly
coloured to ward away potential
predators. This defence works
because most predators associate
bright colours (especially range
and black or yellow and black)
with poison and other unpleasant
properties. This phenomenon is
called aposematism.
In fact, most Coccinellids are
indeed poisonous to smaller predators,
such as lizards and small
birds. A human would have to eat
several hundred Coccinellids
before feeling any effects. |