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Notes: Abstract. 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.

Notes: Summary By summing up the scattered evidence from the literature it is to note that it exists a complete chain of evidence to prove that flies have the capacity to transmit poliomyelitis virus. For it has been observed that the faecal material of infected persons contains the virus, that the flies visit the faeces and are able to pick up the virus, that flies caught in natural conditions harbour the virus, that the virus maintains for three weeks in the fly, that the fly is capable of supporting the multiplication of the virus, that the excrement of the flies contains the virus, that flies visit human food and deposit their excrement in it and that such food eaten by apes results in infection. Some facts support the hypothesis that besides faecal material, carcasses may also play a role as a source of viruses for flies. It is also possible that flies can infect man not only by the oral route but also via wounds. It has been stated that infection via wounds causes paralysis more readily than oral infection. Some facts support the idea that the higher incidence of paralyses in poliomyelitis occurring in the temperate climates should depend on the frequent infection of wounds of susceptible persons by blowflies, which are predominating in the fly fauna of more northern areas. In warmer climates, where houseflies are predominating, the virus is transmitted effectively by flies to foodstuffs. The infection reaches thus the man by the oral route and results most often in a nonparalytic disease. There has been accumulated some evidence for the wiev that fly transmission of poliomyelitis occurs to such a degree that it is of epidemiological significance. It has been observed four times thatLucilia illustris and some other blowflies of this genus has shown a much greater abundance during epidemic years for poliomyelitis than during nonepidemic years. It has also been shown that poliomyelitis occurs significantly later in the southern coastal area of Finland, where the very late flyingLucilia sericata (the species from which poliomyelitis viruses have most often been isolated) occurs, than outside this area. In Finland the outbreak of poliomyelitis epidemics is preceded for about 1–2 weeks by an increase of the abundance of this blowfly and by the ovipositional periods of most other blowflies of the genusLucilia. The occurrence of cloudy days, which are unfavourable for the activity of blowflies, shows a weak positive correlation with the incidence of poliomyelitis. This fact is possibly an indication of the invalidity of the hypothesis of fly transmission of poliomyelitis, but it is also possible that the inhibition of normal ovipositional activity may drive the blowflies to the surface of homoiothermic animals or to human dwellings. Statistics on the changes of theLucilia fauna during the 20th century in Finland show that an increase in their dominance coincided, with the increase in the incidence of paralytic poliomyelitis and the rise in the summer temperatures. Especially the expansion ofLucilia sericata to south Finland coincided clearly with the increase in the incidence of paralytic poliomyelitis. Some facts speak for the comprehension that this highly synanthropic species should be responsible for the fact that the incidence of poliomyelitis is in Finland higher in great cities than in small cities or rural districts. Studies on the effect of fly abatement in poliomyelitis control have remained inconclusive.