Histochemistry and ultrastructure of the mycetome and its 'symbiotes' in the pear psylla, Psylla pyricola Foerster (Homoptera).

The orange-coloured mycetome of the pear psylla, which comprises a cellular covering membrane, a number of mycetocytes and a central syncytium, contains two kinds of inclusions (micro-organisms-in the literature). As DNA could not be detected in them, their status as micro-organisms is questioned. Both kinds contain protein; one kind contains RNA, and (by electron microscopy) tubule-like peripheral maculae. In spite of their anomalous reactions, the inclusions are probably unusual, degenerate or aberrant microorganisms. The biosome theory is invoked in explanation.