FRASS PRODUCTION OF LAST INSTAR LARVAE OF THE BEECH CATERPILLAR, QUADRICALCARIFERA-PUNCTATELLA (MOTSCHULSKY) (LEP-NOTODONTIDAE), AND METHODOF ESTIMATING THEIR DENSITY

The purpose of this study was to investigate frass pr?duction of the b eech caterpillar, Quadricalcarifera punctatella and to develop a metho d for estimating the field density of its last instar larvae from fall en pellets. About 90 % of larval frass was produced during the last in star period. The number of pellets was a better parameter for density estimation than the weight. Pellets wider than 1.8 mm were judged as t he last instar stage. The number of frass pellets produced per day or per hour in the last instar was influenced by many factors: larval age , photoperiod, and especially temperature. However the total number of pellets produced during the last instar was relatively constant (= 63 0) regardless of temperature and photoperiod. The total number of last instar pellets produced per m2 in the season was divided by 630; the quotient gives the total density of the last instar in the season. Thi s method, based on SOUTHWOOD-JEPSON'S graphical method, is very simple but reliable because the estimates are not influenced by temperature, and because the sum total of falling pellets can be estimated correct ly by setting traps throughout the entire season.