Are gregarious red-black shieldbugs, Graphosoma lineatum (Hemiptera: Pentatomidae), really aposematic? An experimental approach


Petr Veselý, Silvie Veselá, Roman Fuchs, Jan Zrzavý


Hypothesis: The coloration of the red-black shieldbug has a warning function. This quality
can be lowered when the shieldbug is presented on a fragmented background.
Organism: We offered wild-coloured and artificially deaposematized (painted brown) red-black shieldbugs (Graphosoma lineatum) to avian predators (Parus major, Parus caeruleus).
Site of experiments: The experiments were conducted in a cage (0.7 m × 0.7 m × 0.7 m) fitted with a one-way mirror.
Methods: In succession, we offered five shieldbugs to each bird. We presented the shieldbugs on contrasting (white) and matching (imitating the shieldbug’s habitat and imitating the striated shieldbug pattern) backgrounds.
Results: The blue tits avoided all shieldbugs offered to them regardless of their coloration. The great tits attacked both colour forms, but the brown one more frequently. The wild-coloured shieldbugs were significantly better protected against repeated attacks. Shieldbugs presented on any of the matching backgrounds were attacked less frequently than when presented on the white background.

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