Nature on our doorsteps: Checks and balances in nature
Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures.
In nature, almost everything is a food source for something else.
Nature can be tough and there are checks in place to keep a natural balance between species.
When prey is abundant, predator numbers will increase and control these prey species. Likewise, if prey numbers drop too low, predator numbers will also decrease.
A particularly fascinating way that nature controls numbers is by using parasites.
Caterpillars of the Cabbage White butterfly can strip cabbage plants bare in no time at all.
In a chemical-free garden, Nature controls these caterpillars using a tiny insect, a small black parasitic wasp species named Cotesia glomerata.
This tiny wasp can lay up to 50 eggs inside the caterpillar and on hatching, the little wasp grubs devour the caterpillar’s insides.
When fully grown, the grubs force their way out through the caterpillar’s skin and spin little cocoons for themselves where they continue to develop into adult wasps.
Amazingly, before the unfortunate caterpillar dies, it is programmed to spin a silky web around the cocoons.
Then, for as long as it continues to survive beside them, it will try and ward off any other predators that might interfere with the cocoons.
No prizes for guessing where the idea for the film Alien might have come from!
