EFFECTS OF CROWDING ON LARVAE OF MEAL MOTH EPHESTIA KUHNIELLA

Ephestia larvae of strain BII (inbred for 140 generations) were obtained at late first or early second instar, and subjected to progressively more crowded conditions. Population sets of 2, 4, 8, 16, 32, and 64 larvae were confined together. In this experiment crowding caused a diminution of body size, an apparent delay in development, and increased mortality. Experiments were also performed with sets of 64 larvae in containers with progressively greater surface area. Areas of 12.6 cm,2 and 144 cm 2 were employed. In some cases weight of food remained constant, in others, the depth. These experiments suggested that the crowding effect was not unimodal. Inhibition of body size remained, while the inhibition of development rate and mortality decreased with increased surface area. A third set of experiments measured the pO2 and pCO2 at weekly intervals in 12.6 cm 2 jars containing 4, 16, 32, and 64 larvae each, and 28.2 cm2 jars containing 64 larvae. A decrease in pO2 was found only at 14 days after isolation in the 32, 64, and 64/28.2 cm 2 jars. When jars of 64 larvae each were flushed continually with air, inhibition was not reduced. Thus the differences in pO2 were judged to be insignificant to the inhibition, and the inhibitor was judged to be non‐volatile. Mortality in the crowded populations was found to result from failure to complete eclosion by pupae behaviorally “trapped” beneath the cocoons of other larvae. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company