Wednesday, 17 April 2013

The Green Shieldbug

Shieldbugs make excellent subjects for study: there are not too many species in Britain; all are easy - or fairly easy - to recognise and there are some very good guide books available. I generally make use of Roger Hawkins' excellent book, "The Shieldbugs of Surrey" which, despite its title, covers all species likely to found in Britain. This morning I saw a roadside specimen which could cause confusion among newcomers to the subject.

Green Shieldbug, Palomina prasina.
Byfield,, 16 April, 2013

The Green Shieldbug is, as you would, expect, bright green in colour. However, this species, which overwinters under dead leaves etc, assumes a cryptic coloration for this period of hibernation. In these brown colours it is presumably less conspicuous to hungry birds. For the summer months (when it feeds on unripe berries) it reverts to an equally cryptic leaf-green. Even if a bird were to find this potential meal it would be unlikely to eat the insect for on the side of the body, a little behind the head, it bears a pair of glands which secrete a foul-smelling fluid. Anyone who clumsily handles one of these bugs will soon become aware of the pong! 

Shieldbugs are true bugs, by which is meant insects with mouthparts modified to form a tube, used rather like a drinking straw.  Most bugs, such as aphids, consume plant juices but many, including the human bed bug Cimex lectularius, obtain their food by feeding on animal fluids. I have recorded the Green Shieldbug from Byfield Pocket Park along with 45 other bug species but this number could be at least doubled with diligent searching - yet another job for this summer.

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