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

Abstract

1. The highest temperature at which Ptinus tectus should be reared is near 24.7° C. 2. Humidities higher than 70 % cannot conveniently be used because of the growth of moulds. Lower humidities prolong development. 3. The best food tried was 95 % whole ground wheat with 5 % dried brewers' yeast. 4. The smallest quantity of this food which permits completion of development is about 3 mg. per animal. This produces miniature adults, one-third of the normal weight, in almost normal time. About 30 mg. is required to produce full-sized adults. These statements apply to individuals reared in isolation. 5. When a group of several larvae are reared in one container, development is prolonged by up to 40 % (which does not occur at all with isolated animals even if food is so short as to cause severe stunting), while some diminution of size (20 %) is found. This is called the ‘group effect’. 6. With groups of 8 larvae, as much as 5 g. of food per larva is required before the group effect disappears, 100 times as much as is needed for full and speedy development by an isolated larva. 7. With quantities of food per larva which are optimal or supra-optimal for isolated larvae, the group effect reaches its highest expression with 8 larvae in the group. It diminishes at smaller group sizes. Mass cultures show the effect to about the same extent as groups of 8. 8. Animals reared in groups show a wider range of variation in size than those reared in isolation, but their duration of development is not more variable. 9. No adequate explanation has yet been found for the group effect and no method has yet been found of producing from mass cultures animals as uniform in size as those reared singly. 10. Adults come into full and fertile lay about a week after emergence from the cocoon. 11. The rate of laying is markedly diminished if the animals are not given fresh food and water to drink daily. 12. A female can live for a year and lay nearly a thousand eggs. 13. In starting mass cultures, it is best to allow a large number of animals in good condition to lay for a day or so. No better result will be obtained by leaving the animals longer.