The Biology and Behaviour of Ptinus Tectus Boie. (Coleoptera, Ptinidae), A Pest of Stored Products

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Abstract
The amount of walking about shown by adult Ptinus tectus is not a simple function of temperature. It depends on culture temperature, on whether the temperature is constant or changing and, with changing temperatures, on the speed and direction of change. Thus, at 20°C., about 25% of animals walk about if the temperature is constant or rising slowly, while about 90% are active if it is rising fast or falling slowly. None of the temperature-activity curves bear any resemblance to the usual kind of Q10 curve. For experiments in which the temperature has been constant for a day the temperature-activity curve of Ptinus rises from 3 to 15°C., then is steady or falling somewhat to 30 or 35°C., and then falls steeply to 40°C. The activity level depends on the temperature at which the animals have been kept during the previous weeks. When the temperature is raised slowly (3-7.5°C. per hour), activity rises steeply up to about 10°C., then falls to the level appropriate to constant temperatures and, at about 30°C., rises steeply again. When the temperature is raised more quickly (14°C. per hour) the activity rise is at first similar to that for slowly rising temperature, but it continues until 90-100% activity is reached at about 15°C.; activity remains at this high level until damaging changes occur at about 40°C. When the temperature is slowly lowered, the activity curve is similar to that for quickly rising temperature. There is thus a stimulating effect of change of temperature--whether rising or falling--the magnitude of which depends on the speed and direction of the change. The results obtained have a considerable bearing on the testing and use of insecticides whose effectiveness depends on the activity of the insects.