2.2.2. Killing and storage
For molecular (DNA) methods, the method of killing does not matter very much, and storage in 95% ethanol is recommended. Diluted EtOH (70%) will work for a limited amount of time, when no 95% alcohol is available, but the bees should be transferred to higher concentrations as soon as possible. Freezing is also possible, but rarely an option when collecting in the field. Storage in any liquid containing formaldehyde or acetic acid destroys DNA and is not recommended (for more details, see also the section ‘Standard methods for immobilizing, terminating and storing adult Apis mellifera’ in the BEBOOK paper on miscellaneous methods (Human et al., 2013)).
For analysis with “classical” morphometry, the bees should preferably be killed by immersion in hot (boiling) water or by ether vapours, because no other method will surely lead to the extension of their proboscis which cannot be measured if not stretched out. In the field, water would keep hot over several hours in a common thermos bottle. The best storage method for morphometric analysis is 70% EtOH, where the chitin stays soft enough for dissection. However, dissection is also still possible after storage in 95% EtOH as recommended for DNA analysis.
For allozyme analysis, the bees should be transported to the laboratory alive, or frozen on site (dry ice, liquid nitrogen) (see also chapter the section ‘Standard methods for immobilizing, terminating and storing adult Apis mellifera’ in the BEEBOOK paper on miscellaneous methods (Human et al., 2013)).