Alfalfa seed production in the northwestern United States and western Canada is heavily dependent upon the pollinating services of Megachile rotundata (F.) (Hymenoptera: Megachilidae). M. rotundata females nest in cavities either naturally occurring or in artificial nesting blocks. Because of the physical nature of the nest, M. rotundata brood may have limited to no exposure to photoperiodic cues in order to regulate important circadian functions. Therefore, various thermoperiod regimes were used to characterize the possible role of thermoperiodism in synchronizing M. rotundata adult emergence. Adult emergence was monitored using a microprocessor-controlled event logger. Incubating bees under constant 29°C and darkness resulted in an arhythmic adult emergence pattern. Exposing developing M. rotundata to a thermoperiod synchronized emergence to the beginning of the thermophase and decreased the total number of days required for all adults to emerge. The amplitude of the thermoperiod regulated the timing of peak emergence in relationship to the increase in temperature. A thermoperiod amplitude of only 2°C was sufficient to synchronize peak adult emergence to take place during the rise in temperature. Increasing the amplitude of the thermoperiod to 4 or 8°C caused a positively correlated shift in peak emergence to later in the thermophase. Brood stored under constant 29°C and darkness for different durations (May or June early in the growing season or July or August late in the growing season) or under a fluctuating thermal regime (base temperature of 6°C and daily 1-h pulse of 20°C until September or November) maintained their capacity for entraining emergence timing by thermoperiodism.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 45 • No. 1