Parents re-emerged sooner at higher densities but the total proportion that re-emerged was independent of density. Over 20 offspring per female were produced at the lowest density (0.5/100 cm2) but only 0.6 per female at the highest density (31/100 cm2). Offspring from the lowest density were about 50% heavier than those from the highest density and also the fat content increased with decreasing density. Females weighed less and contained less fat than males. Male offspring from lower densities produced larger amounts of the pheromone components cis-verbenol and 2-methyl-3-buten-2-ol than males from the higher densities. Offspring from the highest density produced about half as many progeny as those from the lowest densities, showing an effect of density acting over more than one generation. Density-induced variation of beetle 'quality' might be of importance in the population dynamics of bark beetles.-from Authors