Secret Life of the Shield Bug
We spotted this dainty little bug on our runner beans this week and identified it as a young Shield Bug.
The Common Green Shield Bug (Palomena prasina) is a sap-feeding insect common throughout the UK, although rarely found as far North as Scotland. They don't do enough damage to be viewed as a pest by gardeners.
Shield Bugs are so called for two reasons: the adults resemble the shape of a shield and, unlike many insects, they will protect their young from predators. The female of one species even sits on her eggs until they hatch.
The Shield Bug babies are known as nymphs. They go through five different stages of development (also known as instars) before reaching maturity, with a moult between each stage. This one is at stage 4. See here for the complete stages of a Shield Bug's transformation.
In order to digest plant sap, a Shield Bug requires symbiotic bacteria. The young obtain this from an excretion left on the eggs by the mother and ingested when the nymphs eat their way out of the egg.
All this feeding and egg-laying activity inevitably attracts the attention of parasitic wasps, which, given the chance, will impregnate the eggs with their own larvae. This is why the Shield Bug has to shield its eggs!
The Common Green Shield Bug (Palomena prasina) is a sap-feeding insect common throughout the UK, although rarely found as far North as Scotland. They don't do enough damage to be viewed as a pest by gardeners.
Shield Bugs are so called for two reasons: the adults resemble the shape of a shield and, unlike many insects, they will protect their young from predators. The female of one species even sits on her eggs until they hatch.
The Shield Bug babies are known as nymphs. They go through five different stages of development (also known as instars) before reaching maturity, with a moult between each stage. This one is at stage 4. See here for the complete stages of a Shield Bug's transformation.
In order to digest plant sap, a Shield Bug requires symbiotic bacteria. The young obtain this from an excretion left on the eggs by the mother and ingested when the nymphs eat their way out of the egg.
All this feeding and egg-laying activity inevitably attracts the attention of parasitic wasps, which, given the chance, will impregnate the eggs with their own larvae. This is why the Shield Bug has to shield its eggs!
Submitted by Tigger
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