Shield Bugs use bad smell to ward off its predators

By Jim Hurley - Nature Trail

Published 18/08/2015 | 00:00

The Hawthorn Shield Bug is a common green shield bug.
The Hawthorn Shield Bug is a common green shield bug.

While the words 'bug' and 'beetle' are often interchanged to mean some class of creepy-crawly creature, the words do have precise meanings. Both are groups of insects and they differ in both the way they feed and the way their wings are arranged.

Beetles have biting mouthparts and chewing jaws and their wing covers meet in a line running down the centre of their backs. Ladybirds are a common example. In America they are called 'Ladybugs' but they are, of course, neither birds nor bugs.

Bugs have sucking mouthparts like a hypodermic syringe. They insert the syringe into plant tissues and suck up the sap flowing in the vessels within. Their wing covers do not meet in a line running down the centre of their backs; instead the wing covers cross over. Shield bugs are a common example.

Shield bugs get their name from the way their backs look like the shapes of Roman shields used in ancient warfare. And, like Big Bad John in the Jimmy Dean song, they are broad at the shoulder and narrow at the hip.

Shield bugs are also known as Stink Bugs because, like Skunks, they can give off an offence smell. If and when they feel threatened they emit a pungent, foul-smelling liquid through glands on their undersides. Even picking one up to examine it in the hand can result in a lingering bad smell on one's skin.

It is believed that they use the bad smell to ward off birds and other predators that might spot them or sniff them out as potential prey.

The Wexford Naturalists' Field Club has embarked on a project to map the distribution of both ladybirds and shield bugs in the county. The club has already completed surveys of both butterflies and moths and dragonflies and damselflies and has published the results of each of these two surveys in book form.

The plan is that the results of the present project on ladybirds and shield bugs will be published in book form too and all contributions will be acknowledged. To that end, people living in Co Wexford or visiting the county are invited and encouraged to submit records of ladybirds and shield bugs seen in the Model County.

Full details about the Wexford Naturalists' Field Club and their recording activities can be accessed at The website has a page for submitting records online. All records of wildlife in the county are, of course, welcome.

Wexford People

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