Examination of female proportion of light trapped turnip moth (Scotia segetum Schiff.)

The change of the number of turnip moth (Scotia segetum Schiff.) females was examined at 65 different light trap stations between 1957 and 1990. There are two generations of the examined species in Hungary, but the individual number of the first generation is low year by year, so we processed only the data of the second generation. Only those generations were examined that had more than 100 samples because of the statistical reliability. Thirty-three light trap stations were suitable for this examination. The joint number of yearly caught male and female individuals and also separately the samples of females were summarised for each observing station. The change of female individual number as a function of total individual number was determined from the coherent pairs of value. The connection can be described by linear function. The proportion of females is 38%. The relative frequency of females was also determined in the function of the individual number. The shown point-mass is similar to the damped vibration known at technical systems. It was established that the female proportion was higher than the average if the individual number is low, but it showed average value when the individual number was high. It can also be established that the female proportion is significantly high in some cases before gradation years.