THE INCIDENCE OF DIAPAUSE IN 17 POPULATIONS OF THE FLOUR MOTH, EPHESTIA-KUEHNIELLA ZELLER (LEPIDOPTERA, PYRALIDAE)

Samples of E. keuhniella were examined for diapause at 20.degree. and 25.degree. C in continuous darkness, continuous light and 3 other photoperiods. The samples came from 5 flour mills and 5 unheated stores in England, and from Scotland [UK], Egypt, Finland and Japan, together with 3 laboratory reared stocks. Some larvae entered diapause in all but three of the English stocks, in all stocks from other countries, and in a 10-yr old laboratory stock from Japan but not in two other stocks reared in the laboratory for over 30 yr. In continuous darkness at 25.degree. C, the incidence of diapause exceeded 10% in 11 stocks, 25% in 8, and 50% in 3 stocks; in darkness at 20.degree. C the proportions were usually much smaller. In other light regimes there was a much lower incidence of diapause, 10% being reached in only 6 experiments out of more than 80. Markedly more larvae entered diapause when reared on the maize or wheat flour available in mills than on a nutritious laboratory diet of wheatfeed, glycerol and yeast.