Psyllids as a potential source of heavy metals for predators.

Contents of Al, Fe, Zn, Cu, Cd, Mn, Ni, and Hg were determined in 14 species of psyllids and in leaves of their host plants from unpolluted sites (Finland) and industrially polluted sites in Poland. Generally, psyllids accumulated low amounts of metals, but their metal burdens increased with age. Exuvia were important for the elimination of Al, Ni, and Mn, and larval wax for Al, Cu, and Ni. Biomagnification of metals, expressed as the concentration factor (cf) was low (cf: 0.56-1.08) for Mn, Al, and Ni, but high for Cd (cf: 5.86). Trioza chenopodii, Cacopsylla ulmi, and Psylla betulae represented the microconcentrators (cf: 0.9-1.25); the remaining species were the macroconcentrators (cf: 2.0-4.9). In polluted areas Psyllopsis fraxini eliminated large amounts of Al, Fe, Cu, Mn, and Cd with honeydew. This way of metal elimination was of less importance in species from unpolluted sites. Adults of Cacopsylla mali, P. fraxini, P. betulae, and Cacopsylla sorbi fall a prey to ants and may be important in transfer of Zn, Fe, Cu, Cd, and Ni. In comparison with aphids their role in metal transfer is marginal, due to better self-defence mechanisms and higher mobility, which protect them from potential predators and parasites.