In Part I of this paper, the principles of numerical taxonomy are discussed and the practical processes outlined, with particular reference to their applicability to the Fungi Imperfecti.In Part II, one of the authors (J.R.P.) discusses several scoring methods, including one introduced by the authors in which a 'primary' character is weighted according to the number of 'secondary' characters used to describe it. The merits of the various methods are considered.In Part III, one of the authors (W.B.K.) discusses the results obtained when 30 strains of Hyphomycetes belonging to the Leptographium complex were compared using a computer, the taxonomic data being scored in six ways. The classification agreeing most closely with the established one was obtained when 'primary' characters were weighted and 'negative matches' were included. Of the methods applied, this is considered in Part II to be the most logically satisfying.
Laboratory tests, at constant temperatures, were conducted to evaluate quantitatively the influence of temperature on development of the Oriental fruit moth, Grapholitha molesta (Busck). The results showed that at the highest temperature (30°C) some larvae had four instars and some had five, indicating a mixed population. Fifth instar larvae developed only at the highest temperature (30°C) where larval development was also most rapid. It can, therefore, be assumed that the Oriental fruit moth has four distinct larval instars when reared in the laboratory at 15°–24 °C.
Unsprayed apple trees measurably increased the numbers of the Oriental fruit moth, Grapholitha molesta (Busck), in adjacent peach trees in only 1 of 4 years, though the apples were rather heavily infested. The moth became evenly dispersed throughout a previously uninfected peach orchard within three generations. Caged orchard trees were unsatisfactory for studying behaviour because the environment within the cages differed from that in the orchard. Experimental studies indicated that fecundity of the females was variable between years and generations and a varying proportion laid no eggs. Intraspecific competition between newly hatched larvae occurred at low egg densities; egg mortality was small but mortality of newly hatched larvae was large.
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