REARING OF HONEYBEE LARVAE IN VITRO: EFFECT OF YEAST EXTRACT ON QUEEN DIFFERENTIATION
HEINZ REMBOLD AND BERND LACKNER
First instar honeybee larvae (60 per test) were reared ill vitro under controlled conditions. The yield of adults was 70-80%, and 10% were queens if royal jelly was used, diluted 1:1 with water and supplemented with D-glucose and D-fructose (2·5 g in 40 g test food). Difco bacto-yeast extract (0,5 g) or charcoal-treated extract (1 g) were added to this basic food. At the same rate of survival, larval growth and queen determination were considerably increased (30% and 50% queens). The charcoal-treated yeast extract was separated by gel chromatography into a salt and an amino acid fraction. The salt component reduced the yield of adults to about 50% ,but it increased larval growth rate and differentiation (20% queens). The amino acid fraction reduced the rate of survival to about 30%; growth rate and caste differentiation were below those with the basic food. Addition of both fractions gave the same result as addition of charcoal-treated yeast extract. The average gain in weight of 4th to 5th instar larvae was related to the degree of caste differentiation. For routine tests, use of a mixture of royal jelly, water, sugar and yeast extract yields more than 30% queens, at a survival rate from 1st instar worker larvae near 80%, under controlled in vitro conditions.