From the introduction:
"The key in the present publication is a revised version of its immediate predecessor in the series (Macan 1965a). This work itself was a development of earlier keys by Macan (1939, 1941, 1956). Experience of using Macan (1965a) with some thirty cohorts of students in tertiary education and teachers in both primary and secondary schools suggests that its fundamental structure is satisfactory. However, this experience has resuited in many detailed changes in the text and considerable rearrangement of, and additions to, the illustrations.
The main change in the key itself is the inclusion of a newly described species, Corixa iberica Jansson, 1981. It was initially described from specimens from the South West Iberian Peninsula but was later noted in British material (Jansson 1986). The specimens noted by Jansson have been examined together with thirty-seven further specimens discovered in existing collections. British material has been used in the construction of this key. It is also noteworthy that Limnoporus rufoscutellatus (Latreille), already included in the key, now may be regarded as a member of the indigenous fauna (O'Connor 1986).
A major change in the work as a whole is the inclusion of a substantial section on the ecology of water bugs. There have been important developments in the study of these insects in the past two decades, particularly in our knowledge of the group. The inclusion of recent work has necessitated the exclusion of detailed reference to much of the earlier work but it may be traced from the references given. In particular, Southwood & Leston (1959) is a valuable national source while the accounts of semi-aquatic bugs (Andersen 1982) and Corixidae (Jansson 1986) provide a broader perspective."