Shieldbugs are popular and readily identifiable insects found on the reserve at St Nicks, and can be seen in most months of the year. Unlike beetles, shieldbugs tend not to scuttle away when observed but will pose for photographs. They superficially resemble beetles but are actually part of the bug tribe. All insects are sometimes referred to as ‘bugs’ but while beetles seize and chew their prey, and flies have spongy suckers, most true bugs like the shieldbugs have piercing mouthparts with which they feed by penetrating plant tissue or the skins of grubs and caterpillars. Most shieldbugs are vegetarian.
The UK has 32 species of shieldbug, but many of these are either very rare or confined to southern counties. They are sometimes called stinkbugs because they have an anti-predator strategy of emitting a foul-smelling fluid when threatened.
Nine species have been spotted at St Nicks in the last 12 months. Some, like the Birch, Gorse, Hawthorn, Sloe and Woundwort shieldbugs, are named after the plant on which they feed and lay their eggs; others, like Common Green, Parent, Pied and Spiked, take their name from their appearance or habits. As can be seen from the photos (all taken at St Nicks during 2013 and 2014) shieldbugs are aptly named. The Hawthorn Shieldbug is the largest of those seen at St Nicks, being twice as large as the beautiful shining bronzy-purple Woundwort Shieldbug. The most frequently seen is the Common Green.
Most shieldbugs hibernate through the winter as adults, and emerge in the spring to mate and lay eggs. This is when they are most active and can be easily be seen from March to June. Most adults then die, leaving their eggs to hatch into tiny larvae called nymphs. One species, the Parent Bug, guards its eggs and looks after the nymphs until they can fend for themselves. On several occasions this year the Wednesday Wildwatch group has found female Parent Bugs guarding both eggs and young.Unlike butterflies or ladybirds there is no pupa or chrysalis stage: the nymphs go through 5 or 6 changes of skin until from July and August they are fully-fledged adults.
From August through to October the new adults can frequently be seen resting on leaves or twigs, or feeding up to gain strength for their winter hibernation. They have wings, but are not often seen in flight. At St Nicks the Gorse Shieldbug (which is a reddish colour in the summer, but changes to green in the spring) has been seen in every month of the year except February: sunshine brings it out even in December and January.
This summer look out for three shieldbugs not yet recorded at St Nicks: in the meadow areas the pale green Bishop’s Mitre (looking just like one) and, along the woodland paths, the unmistakable metallic-looking Blue Shieldbug and the larger conker-brown Forest or Red-legged Bug.