David E. Leonard

EFFECTS OF DENSITY OF LARVAE ON THE BIOLOGY OF THE GYPSY MOTH, PORTHETRIA DISPAR

The crowding of larvae of Porthetria dispar in laboratory cultures induced physiological and morphological differences. Larvae which were crowded developed faster than isolated larvae, but the development of instars varied in a characteristic manner. In crowded larvae (1) instar I was longer, (2) instars II–IV were shorter, (3) in males the penultimate and last instar were shorter, (4) in females the penultimate and last instar were longer, (5) in both sexes the pupal period was shorter. The pupal weights from crowded larvae were less, indicating a loss of fecundity. Crowding larvae increased the percentage of larvae which had increased survival. Phalaris tuberosa tended to cause high mortality in Rhopaea. Trifolium than the coloration of adults reared in isolated cultures.

Effects of starvation on behaviour, number of larval instars, and developmental rate of Porthetria dispar

Abstract The behaviour, number of larval stadia, and developmental rate of the gypsy moth, Porthetria dispar , can be altered by deprivation of food. The behavioural change is an increase in locomotory activity associated with hunger. The number of larval instars can be increased by food deprivation during instar I, but in instars II, III, or IV no significant increase was obtained. Food deprivation early in instars II, III, or IV reduced the numbers of subsequent ecdyses. When food was withheld early in an instar, the rate of development was accelerated during the remainder of the instar. The removal of food just before the cessation of feeding prior to apolysis also accelerated development.