The effect of nest replacement on the production of females of the alfalfa leaf-cutter bee Megachile rotundata (F)

S. C. Jay And N. Mohr

Partially filled hives, containing cells of Megachile rotundata (F) brood, were replaced with empty hives early in the field season in an attempt to obtain an increase in the number of female alfalfa leaf-cutter bees. The frequency of female bees decreased from the back of the tunnels to the front ends in both the original and replacement hives; male bees showed the opposite pattern. Ratios of male to female bees ranged from 1.6 : 1 to 3.0 : 1 despite the use of tunnels of standard length and diameter. There was no significant increase in females produced in the replacement nests suggesting that it is neither feasible nor economical to replace nests to increase numbers of female bees. However, chalcidoid parasitism (by Pteromalus venustus Walker) was significantly reduced in the replacement hives, possibly owing to the method used to remove bees from the original hives.