Artificial Selection for Weight and its Consequences in Tenebrio molitor L.

Abstract

BEGINNING in 1946 a population of Tenebrio molitor (Coleoptera, Tenebrionidae) was reared continuously in standard optimal or sub-optimal conditions of food, temperature and humidity, avoiding as much as possible interferences of cannibalism and overpopulation. At the same time, artificial selection in favour of small and big pupal weights was undertaken and resulted in splitting the initial population into two strains, one labelled F (small weights), the other labelled G (big weights). The first eight years were mainly devoted to this work of selection, consisting in the removal of all F-pupæ weighing more than 160 mg, then more than 130 mg, and of all G-pupæ weighing less than 160 mg. From 1952 on, after about 12 consecutive generations of both strains, both appeared definitely homogeneous and no further selection was needed save in quite exceptional instances¹. It had also become obvious that by selecting for weights one had also selected automatically in favour of shorter or longer durations of larval development. Further attempts to split the two strains in order to obtain dwarf strains failed². Thus time had come to find out whether the two strains differed also in other respects. They do so indeed, to an extent that it is now possible to formulate a true physiological diagnosis involving quite a number of unexpected characters.