Tuesday, 27 April 2010

Welcome back Ladybirds

As soon as the first rays of sunlight appear in Spring, the ladybird leaves its nest where it been hibernating during the winter. There is just one thought on its mind, to reproduce. The male flies around to find a female, when found, grips her tight and settles himself firmly on her back, and starts fertilising her eggs. This operation can take several hours.

If he leaves too soon, another will arrive to finish the job. As soon as the fertilisation of the eggs is completed, the female ladybird searches for the nearest colony of aphids and deposits 50 yellow eggs very near to them. This whole operation takes place several times during her productive period.

To realise the size of the eggs, the red point is the head of a matchstick.

After 5 days, the eggs become grey, a transformation, which announces the arrival of the larvae.
The larvae is blue-grey in colour, eats its way out of the egg, devours what is left over of the egg, and as it makes its way towards the aphids, it gulps down a few of its sisters. But its main interest lies in eating as many aphids and other sucking insects as it can, which it manages to do in record time. The larvae eats 100 aphids per day.

A ladybird larvae

As a comparison an adult ladybird only eats 5000 aphids during its lifetime (about 2 years). The larvae sheds its skin 4 times in 1 month. After the shedding is finished, it glues itself onto a twig (glue is produced by its abdomen), the pupal stage has arrived.

Pupal stage

After 8 days, the ladybird brakes out of the shell. Little by little the black spots appear on the new born ladybird, it takes several hours before the shell has turned red. The red is to frighten off its preditors especially birds. When disturbed or attacked the ladybird ejects a yellow liquid that has a disagreable smell and tastes bitter. This defense does not work with ants, spiders, bugs and other insects. Flies and certain type of wasps even lay their eggs directly into the ladybird's body, parasiting it.

The ladybird with 7 spots is the most common ladybird, but there are about 80 different type of ladybirds in France alone (3000 known species in the world). Ladybirds come in all sorts of colours, red, yellow, orange, pink or black with 2 to 22 spots.

Be aware of the Asiatic ladybird. It was imported in the beginning of the 20th century , then used on a massive scale in the 1980s as a biological control against aphids, it has become invasive and is eliminating certain native species.

An Asiatic ladybird comes in different shades and number of spots

In biological control against aphids, it is enough to use two to three European ladybird larvae to control an aphid invasion as they eat 100 aphids each per day. Before you deploy them you need to make sure there are aphids around (normally in April), if not, there is nothing for the larvae to eat. A smal paintbrush can be used to deposit the larvae on to the plants and fruit trees. Make sure that there are no ants about as they seem to protect the aphids from the larvae. The larvae can be obtained from specialised shops or from OPIE (Office Pour les Insectes et leur Environnement) tel : 01 30 44 13 43 www.insectes.org

Bibliograhy : Rustica, Bienvenue aux coccinelles by Colibri et Alain Raveneau

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