Look out for gorgeous little Brassica Bugs on crucifer species, such as Scurvy-grass or Garlic Mustard.
Photo: Sally Luker
Scientific name: Eurydema oleracea
Other common names: Brassica Shieldbug, Cabbage Bug, Crucifer Shieldbug
What to look for:
- Colouring : A metallic sheen of deep blue/green with spots and a paler margin. There is variation in the colour of the spots, which can be orange, red, yellow to cream and white.
- Size : 6 to 7 mm long, 4 mm wide.
- Where : Mainly in the south and centre of the UK. Globally, its distribution includes West Europe, west and central Asia and northern Africa.
- When : From spring to autumn. They are dormant through the winter, usually hiding away in leaf latter or small cracks and holes.
- Similar species : Other shieldbugs. Some instars are similar to Eurydema dominulus
If you spot some wild crucifer (cabbage) species when you’re out walking, Garlic Mustard or Scurvy-grass for instance, take a close look and see if you can find the delightful little Brassica Bug. With its deep blue or green metallic sheen and markings of cream or, less commonly, orange-red, this shieldbug emerges from its winter dormancy amongst the leaf litter as spring warms the air and its host plants open out their foliage.
It’s pretty obvious how shieldbugs got their common name, with their five sides and flattish shape, just like a heraldic shield. Sometimes confused with beetles, they are an entirely different order altogether. Shieldbugs are True Bugs, distinguished by having piercing/sucking rather than biting/chewing mouthparts.
The Brassica Bug belongs to the Pentatomidae, otherwise known as the True Shieldbugs. The larger Green Shieldbug, more common and the one many people will recognise from their gardens, is also a member of this family.
After emerging in the spring and mating, the females lay their eggs on the host crucifer plants. Generally laying her eggs in neatly lined-up double rows of 10 to 12 eggs over a period of a month to six weeks, the female may eventually deposit around 80. The young – the nymphs and early instars – moult five times, in the later stages having a striking colouration of yellow and black, before achieving adult colouration at maturity. The adults themselves show colour variation in their spots and edging: this is clearly shown in the photograph to the left, in which one of the two mating adults has red spots and the other pale cream.
Brassica Bugs feed on the seeds of their host plants, so they can sometimes be a nuisance to allotment gardeners or commercial growers. However, they are more often found on wild varieties.
Did you know…?
…There are over 40 species of shieldbug recorded in Great Britain.
…In the USA, some species of shieldbug are called stinkbugs because of their ability to emit foul-smelling chemicals from glands behind their hind legs. They use this as a defence against predators.
More information and references:
Chinery, M., 2005. Collins Complete Guide to British Insects. HarperCollins, London.
Published: April 2015
Author: Amanda Scott
Photos: Sally Luker