Distribution of Trogoderma granarium (Col. Dermestidae) at constant humidity and in gradient of humidity

The distribution of males and females of Trogoderma granarium beetles in a humidity gradient and at constant humidity was examined. Distribution was not uniform at constant humidity as the beetles usually aggregated at the margins of the apparatus. In a gradient the beetles collected most abundantly where the humidity was low. The initial distribution of beetles at the beginning of the experiment (whether located at the centre or dispersed uniformly along the instrument) influenced the response and the subsequent behaviour. The response vs. time curve indicates an excessive activity in the different humidity regions in the 10-100 per cent range and a decrease in response in each humidity region with time. At 0 per cent r.h. the activity appears to be normal along the entire instrument and the response increases systematically with time. Aggregation due to an olfactory factor influences the humidity reaction of Trogoderma granarium beetles.