THE EFFECT OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND MORTALITY OF TRIBOLIUM CASTANEUM (HERBST) (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Triboliicnz castaneum were studied over a series of temperatures between 15 and 40 degrees C. at 10, 30, 70 and 90 % R. H. using wheatfeed as food. Eggs did not hatch at any humidity at 17.5 degrees C. or less, nor at 10 % R. H. at 40 degrees C. At all other conditions about 80 % of eggs hatched. Humidity does not affect the duration of the egg period. The effect of temperature on the egg period is shown graphically, the shortest period occurring at 3 7.5 degrees C. Larvae fail to develop into normal adults at 20 degrees C. and also fail at 90 and 30 yo R. H. at 40 degrees C. At 20 degrees C. and 70 % R. H. pupae may be formed but they do not become normal adults. The rate of larval development is affected by both temperature and humidity. Development is quickest at the highest humidity used at any temperature and at 35 degrees C. for each humidity. Larval mortality is less than 20 % except at 40 degrees C. and at combinations of low humidity and low temperature. The results correspond with published results using similar foodstuffs. Groundnuts were used as a food in a series of experiments at 30 degrees C. and another series at 70 % R. H. Larvae on this food were much more susceptible to the effects of humidity and were unable to develop at 20 or 40 degrees C. at 70 % R. H. In all conditions development was slower and mortality higher than on wheatfeed. The pupal period is not affected by humidity and is shortest at 37.5 degrees C. The conditions in which Park found that cultures of T. castaneum became extinct, 24 degrees C. and 30% R.H., lie inside the zone in which development is possible. The possible causes for this discrepancy are discussed.