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Some aspects of the biology of the Bruchid beetle, Caryedon gonegra (Fab.), have been studied. The Bionomics were observed at 30°C, 40°C and 45°C, and 50, 70% and 90% 17..H., and about 27.5°C, 75% R.H. Studies on competition were made in the latter conditions. Preliminary work included studying the relationship between the head dimensions of the larvae and of the instar reached; between live, dead and dry weights, and percentage of weight lost, of mated and unmated adults (males and females) was analysed (linear regression analysis). The bionomic studies were concerned with the influence of high and optimal temperatures and relative humidities on the longevity and fecundity of the adults, as well as with egg-survival and with the incubation period; the influence on these of the presence or absence of food was also determined at the optimal conditions. The duration of the mating period, the rhythm of oviposition and the types of egg destruction were also determined. The competition between adults was analysed by its effects on the longevity of the adults, their oviposition and the survival of their eggs. The larval competition was the most important part of the work, the following phenomena being studied in most detail: place of pupation, developmental period and mortality, live weights of adults (F1), and behaviour of competing larvae. Finally, some observations were made on the phenomena of dispersal.