EFFECT OF DIFFERENT NARCOSIS PROCEDURES ON INITIATING OVIPOSITION OF PREDIAPAUSING BOMBUS-TERRESTRIS QUEENS

Four experiments aimed at the stimulation of starting oviposition were carried out with bumblebee queens (Bombus terrestris L.) from colonie s belonging to the ecotype of Central Western France and reared in a g lasshouse. After mating, queens were narcotized with carbon dioxide, c onfined singly in small boxes (11 x 5 x 4.5 cm) and kept in a dark roo m at 28-29 degrees C and 60 %-65 % r.h. They were fed on a sugar solut ion and a pollen-syrup mixture. No effects were discernible if the nar cosis was applied 20 to 30 days after mating instead of 5 days, nor if the queens were submitted to a 4 to 5 day period at 34 degrees C foll owing narcosis. Survival rates ranged from 65 % to 68 %. If the queens were reared under fluorescent tubes (L8:D16) after narcosis the mean delays to egg-laying were significantly reduced compared to a dark tre atment (21 days instead of 39), as was their variability (s.e.=1.6 day instead of 3.1 days). The survival rates were respectively 73 % and 6 7 %. Under the same photoperiod (L8:D16) the CO2 narcosis repeated at a 24h interval had the same efficacy whether its duration was 10 min o r 5 min. The delays to egg-laying were respectively 20 days (s.e=1.5) and 25 days (s.e.=4.8) with survival rates close to 73 %. Egg-laying c ould also be induced in non-narcotized queens with a survival rate of 54 % and delays to oviposition close to those of queens narcotized 2 x 10 min.