Nature on our doorsteps: A clever way to protect the young
Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.
The young of many species in nature are very vulnerable. They must avoid a range of different predators and they need a steady supply of food to help them grow quickly.
Some insects, like the gall wasps, have evolved a very clever way of ensuring that their larvae have both plenty of food and a safe place in which to develop.
They do this by making another species provide it for them.
Gall wasps are fascinating little insects that should not be confused with the more familiar yellow and black stinging wasp.
Gall wasps are very small, often less than 4mm long. They do not sting, and they largely go unnoticed by us.
There are different species of gall wasp, and most are specific to a particular species of plant. The leaves and buds of Oak, for example, support a range of different gall wasp species.
Robin’s Pincushion gall on Wild Rose is a distinctive spiky-looking swelling
The female gall wasp lays her eggs in the leaves, buds or under the stems of her chosen plant.
When the larvae hatch, they emit a special chemical which makes the plant respond very quickly to protect itself. The plant rapidly produces many new plant cells around the larvae, enclosing them and isolating them from the rest of the plant.
This is exactly what the larvae want.
They are now hidden away, protected from predators and bad weather in a swollen structure called a gall.
They develop in their own separate chambers and, as the swelling is made from thousands of plant cells, the larvae have a plentiful supply of food.
When the larvae are fully developed, the adult wasp emerges through a small hole in the gall and flies away.
Different species of gall wasps produce different sizes and shapes of gall swellings.
Twigs of Oak trees, in particular, often carry Oak Apple Galls, while the very visible, spiky-looking Robin’s Pincushion gall occurs on Wild Rose.
