EFFECTS OF MATING STATUS, SEX-RATIO, AND POPULATION-DENSITY ON LONGEVITY AND OFFSPRING PRODUCTION OF CRYPTOLESTES-FERRUGINEUS (STEPHENS) (COLEOPTERA, CUCUJIDAE)

The life span and reproductive rate of the rusty grain beetle, Cryptol estes ferrugineus (Stephens), were determined at different adult densi ties and sex ratios at 30 +/- 1-degrees-C, 75 +/- 5% relative humidity (RH), and with feed consisting of ground wheat plus wheat germ (4:1, w/w). The mean life spans of adult beetles were 32 weeks for adults in dividually isolated in separate vials, 22 to 25 weeks for adults of di fferent strains kept one male and one female per vial, 24 weeks for a group of 30 virgin females together in one vial, 13 weeks for a group of 30 virgin males together ih one vial, 14 weeks for groups with 10 m ales and 20 females per vial, 13 weeks for groups with 15 males and 15 females per vial, and 12 weeks for groups with 20 males and 10 female s per vial. When kept one adult per vial, males and females had simila r life spans: when kept one male and one female per vial, males lived longer; when kept in groups of 30 per vial females lived longer, excep t in the group which had a sex ratio of two males to one female; in th is group life spans of males and females were the same. Females in sep arate vials with one male produced mean numbers of offspring ranging f rom 389 for an inbred homozygous malathion-resistant strain to 514 for an outbred strain (genetically variable: GV). GV strain females in vi als which had 10 males and 20 females produced a mean of 97 offspring, GV strain females in vials which had 15 males and 15 females produced a mean of 146 offspring, and GV strain females in vials which had 20 males and 10 females produced a mean of 216 offspring. The results of this study and similar studies on other insect species suggest that th e life span of this insect is inversely related to the rate at which i t expends energy and to injury incurred during copulation, and that ov iposition rate decreases as the density of larvae and female adults in creases.