How dicyphine mirid bugs (Heteroptera, Miridae) attach and walk on adhesive hairy plant surfaces

Representatives of the mirid bug subfamilies Orthotylinae and Bryocorinae are known to be specialised in living on adhesive plants. Such bugs have been reported to bear elongated, curved, sharp claws and free, rather large pseudopulvilli. Besides specialised claws, they have slim bodies, as well as long, slender legs contributing to avoid contact formation with sticky plant secretions. Additionally, they have some behavioural specialisations. For example, generalist bugs Dicyphus errans Wolff, living on a broad range of plant species, stalk along plant surfaces touching only trichome tips and stop frequently to groom themselves. In contrast, the South African species Pameridea roridulae Reuter is specialised to live on the protocarnivorous plant Roridula gorgonias Planch. (Roridulaceae), highly efficient flypaper trap. Its habit and behaviour differs dinstinctly from related mirid species. The combination of structural and experimental studies revealed two locomotion strategies in mirid bugs from the tribus Dicyphini on the adhesive plant surfaces: (1) avoidance strategy, characterised by the slim body held at a large distance from the plant surface by using long, slender legs, and (2) defense strategy, where trapping of heavy bugs, situated close to the plant surface, is overcome by generating strong attachment forces to the plant cuticle by using pretarsal structures and by having a thick greasy cuticle layer preventing adhesion of plant trichomes to the bug surface.