This paper presents the life tables for sexually isolated males and females of the ''tobacco beetle", Lasioderma serricorne F., based on insects that lived in vials maintained in an incubator at 30°C and 85% of relative humidity, in the dark. The adults were obtained from three different cultures ; the immature stages were fed on wheat flour. For each culture the females were always longer-lived than the males (P = .01). The mean life durations for males from cultures a, b and c were respectively 23.06, 24.63 and 19.66 days. Males from cultures a and b showed no statistical difference in their life duration (P = .01). The mean life durations for females from cultures a, b, and c were respectively 33.63, 26.53 and 21.18 days. Those means are statistically different (P = .01). Males and females from cultures c were shorter lived (P = .01) than males and females of both cultures a and b. Considering the fact that the original number of beetles from culture c (382 males and 330 females) was much larger than the original number of beetles from culture a (171 males and 157 females) or b (146 males and 184 females), we know that the density of the larval population in the culture c was higher than in the culture a or b. Competition during the larval stage must be the chief factor responsible for the shortening of the mean adult life for both sexes of L. serricorne F. from culture c as compared with the mean adult life of adults from cultures a and b, less densely populated during the larval stage. This observation agrees with the criticism of Wright, mentioned by Allee, Emerson, Park and others (1) concerning the importance of exogenous events in the pre-imaginal period of the life duration of the adults. The data show that L. serricorne F. is an excellent material for studies on physiological longevity, because the adult beetles do not feed. For toxicological studies this insect species also seems to be a very appropriate material, as it is well brought out by the survivorship curves.