Effects of chlortetracycline of honey bee worker larvae reared in vitro

An in vitro method was developed for rearing worker honey bee ( Apis mellifera L.) larvae to the adult stage. Average larval and postdefecation mortalities were 9.5% and 18.1% respectively. Larval and postdefecation development times were similar to worker brood reared in field colonies. Only 1 of 30 sampled adult bees exhibited queen or intercaste characteristics. The in vitro rearing method subsequently was used in studying the effect of the antibiotic chlortetracycline on larval growth and development. A general dose response was observed in mortalities of larvae fed diets containing 0.0025% to 0.05% chlortetracycline. At 0.0025%, larval and postdefecation mortalities were similar to the controls. At this concentration, chlortetracycline effectively reduced larval and postdefecation mortalities of larvae inoculated with 1 × 10 4 to 1.5 × 10 8 spores/ml of Bacillus larvae, the causative pathogen of American foulbrood disease. Chlortetracycline doses higher than 0.0025% retarded larval growth and development and caused precocious pigmentation in early larval instars.