Oecologia (Berlin) (1984) 63:75-79 Oecologia 9 Springer-Verlag 1984 Factors affecting pupal survival and eclosion in the pine beauty moth, Panolis flammea (D & S) Simon R. Leather Forestry Commission, Northern Research Station, Bush Estate, Roslin, Midlothian, EH25 9SY, UK Summary. The proportion of adult Panol&Jlammea emerg- ing from the overwintering pupae was markedly affected by pupation substrate, waterlogging, temperature and rela- tive humidty. Pupae which had spent the winter in needle litter had a significantly greater survival rate than those in either soil or peat. The greater the length of time spent waterlogged the greater the mortality rate of P.flammea pupae. At tempera- tures of -20 ~ C, there was 100% pupal mortality within 24 h of exposure. Pupal weight loss was proportional to the length of time spent as a pupa. Female pupae lost proportionately more weight than male pupae. Pupae of both sexes lost more weight at a low relative humidity than at a high relative humidity. At low relative humidities female pupal mortality was higher than that of male pupae. Introduction The pine beauty moth, Panolis flammea (D &S) (Lepidop- tera: Noctuidae) is one of the most serious pests of Scots pine, Pinus sylvestris L, in Central Europe (Klimetzek 1972; Altenkirch 1978; Schwenke 1978; Priesner et al. 1978 ; Da- joz 1980) and has caused considerable damage in Sweden (Lekander 1954) and Finland (Saalas 1949). In recent years P. flammea has become a serious pest of Lodgepole pine, Pinus contorta Douglas, in northern Britain (Stoakley 1977, 1978, 1979). P. Jlammea overwinters as a diapausing pupa in a lightly constructed hibernaculum in the needle litter/soil interface (Zw61fer 1931; Saalas 1949; Stoakley 1977, 1979). In sites such as this the overwintering pupae are likely to encounter a wide spectrum of conditions ranging from prolonged wa- terlogging, freezing in water and exposure to low tempera- tures. The degree to which the pupae will experience these conditions is likely to depend on pupation depth and sub- strate. Overwintering mortality from any one of these condi- tions could be a major factor determining the number of adults likely to emerge the following spring. The numbers and condition of the adults emerging is of great importance in determining the subsequent number of larvae. This paper reports laboratory and field experiments on the effects of low temperatures, waterlogging, pupation depth and substrate on the success of pupal eclosion in P. flammea and relates this to the situation occurring in the field. Methods and materials a) Pupation substrate. Ten healthy pupae of P. flammea were placed in a wooden sided box (19 cm x 14 cm x 7 cm) with top and base of insect-proof netting. Each box was filled with either P. contorta needle litter, a clayey loam or peat. The pupae were distributed uniformly at a depth of 3.5 cm in each box and the boxes were then sunk level with the soil surface in a 15 year old stand of P. contorta. Ten replicates of each substrate were used, and were placed in position during the first week of September 1982. The number of successfully emerged moths was assessed at the beginning of May. b) Waterlogging and pupation depth. Ten healthy pupae were placed in wooden boxes as above, filled with P. con- torta needle litter. The pupae were distributed uniformly at depths of 1, 7, 10 and 15 cm below the surface as con- trois. In addition, pupae buried at depths of 1 and 7 cm were protected from rainfall by replacing the netting top on their boxes with a plastic cover. A further group of pupae at 1 and 7 cm depth were soaked with 1,000 ml water every two days. The boxes containing the pupae were placed in a stand of P. contorta at the beginning of September and were assessed for eclosion success at the beginning of May as above. Ten replicates of each treatment were used. c) Temperature and waterlogging. Healthy pupae of P. flam- mea were removed from an insectary and placed in groups of ten in small (80 ram) sealed plastic containers at 0 ~ C, -10 ~ C and -20 ~ C. In addition, at each temperature, pu- pae were buried in either dry or waterlogged peat, care being taken to ensure that an equal amount of substrate was above and below the pupae. The pots containing the pupae were removed from their respective temperature regimes and placed at 20~ 16 h photoperiod after 1, 2, 3, 7 and 10 days. The time to eclo- sion and relative survival rates were recorded. d) Duration of waterlogging. Healthy pupae were removed from an insectary and placed in groups of ten into small plastic pots containing water for i, 3, 5, 7, 24 and 96 h