Pupae ofEphestia cautella(Walker) andPlodia interpunctella(Hübner) were brief1y exposed to temperatures of 40, 45, or 50°C, and the effects on adult eclosion, mating, fecundity and fertility were determined. All males and females of both species were killed by a 2-h exposure to 50°C, butE. cautellawas significantly more tolerant of exposure to 40 and 45°C thanP. interpunctella. The median lethal time for exposure to 45°C was 7- to 8-fold longer inE. cautellathan inP. interpunctella. Generally, exposure of male or female pupae of either species to high temperature caused some failure to mate and reduced the fecundity of mated females but did not reduce hatchability of the eggs laid. The percentage of mating failure depended to some extent on which sex was exposed and increased with temperature and length of exposure. Loss of fecundity was usually more severe when females rather than males were exposed.