Juvenile hormone biosynthesis and diapause termination inBombus terrestris

Summary Corpora allata from female Bombus terrestris, incubated in a medium containing L-[methyl-3H]methionine, released three radiolabelled products, one of which was identified as JH-III by RPLC analysis. Two others did not correspond to any JH analogues or JH-related compounds, and they remain unidentified. Exogenous farnesol stimulated JH-III biosynthesis and suppressed the synthesis of the two unidentified products. Corpora allata activity was monitored throughout and after adult diapause. Rates of JH-III biosynthesis were low during prediapause and diapause. Corpora allata reactivation occurred several days after emergence from soil and thus seemed not to be involved in diapause termination processes. Experimental diapause breakdown revealed two phases in imaginai Bombus diapause: diapause development and post-diapause quiescence. Carbon dioxide narcosis associated with 20°C, 13L/11D conditions provided rapid and reliable diapause termination in both diapause phases. The mode of CO2 narcosis action is not mediated by corpora allata reactivation and remains to be elucidated.