The Common Green Shield Bug

Palomena prasina, or common green shield bug (Order: Hemiptera; Family: Pentatomidae), belongs to the most important family of shield bug. From above they are mostly rounded or more or less oval shaped, whereas from side-view the back surface is somewhat flattened, and the underside somewhat convex. They are bright green in colour, but in late autumn the adults turn brown before going into hibernation.

In April to May their colour changes back to green before they 'wake up' from hibernation.

The newly-hatched larvae are yellow at first, but within a few hours turn black to the front and brown to the rear. They remain clustered on their egg shells for several days, feeding from the eggs' surfaces. With this behaviour, they infest themselves with the necessary symbiotic bacteria which the mother smeared on the eggs as she laid them.

Photo Marlies Vaz Nunes - all rights reserved

Later, the nymphs also loose the black front and become completely green.

This bug likes especially warm summers and dry winters, and warm summers in particular can cause their numbers to increase dramatically: we found them on almost every kind of plant in the garden at the end of the long hot summer of 1995 in southern England.

Like its relatives, this bug is well-known for its ability to produce foul-smelling volatile secretions. These secretions are produced by adults as well as larvae to repel their enemies, and are left everywhere they go. For this reason they are also known as stinkbugs.

In spite of their sometimes large numbers and the fact that they suck plant sap, P. prasina does not cause much damage. However, they also like to suck on soft fruits, such as raspberries and blackberries. Their stinking excretion renders the fruits smelly and gives them a bad taste.

Adult shield bugs can be parasitised by tachinid flies (Order: Diptera; Family: Tachinidae), especially by Phasia Hemiptera. These flies are medium to large in size and many look like bristly houseflies. The adults feed on nectar and other plant exudates, and some species also feed on honeydew. Females lay a single egg inside or on the surface of the bug.

The newly-hatched maggots, which like all maggots are legless, hatch within a short time, and burrow inside to feed on the juices in the body cavity of the host. Later, in their third and final stage, the maggots also eat solid materials of the host. They leave through a split between the segments of the host's abdomen, at which stage the host is of course already dead. The maggots immediately burrow into the soil to pupate.

There is nothing specific that can be done against the green shield bug which, luckily, is hardly damaging anyway. The best one can do is to attract tachinid flies by growing flat-topped open flowers, such as daisies, sweet clover, dill, or parsley.