3.1.4. Material and its preservation
For guidance on how to collect bees, see the BEEBOOK paper on miscellaneous methods (Human et al., 2013). Freshly killed bees will be available for dissection at all times, and even in the depths of winter can be collected from the cluster. With the exception of queens and drones, preserved bees are more satisfactory for dissection. Bees outside of preservation fluid deteriorate quickly, so bees that are intended for autopsies need to be collected alive and appropriately preserved. Black bees, or dark hybrids, are easier to dissect than pale races, the internal sclerotized parts being more deeply coloured and therefore more conspicuous. Queens and drones must be dissected immediately after killing; their reproductive organs become brittle when they are preserved by any method, and thus break up when they are disturbed.
Alcohol is commonly supposed to be a good preservative. This is a fallacy. It does not penetrate sufficiently rapidly to prevent the onset of decomposition, which ensues very rapidly after death, and it renders tissues very brittle. It is therefore necessary to add to the alcohol some substance which has great penetrating power and which tends to toughen tissues. Two such fluids are commonly used, formalin and acetic acid.
Formol alcohol is prepared by mixing the following:
- 95 % alcohol 70 parts by volume
- formalin 5 parts
- water 25 parts.
The formalin penetrates quickly, and hardens soft tissues, making them leathery and easy to handle. This fluid can be used not only for preserving material, but also for fixing and hardening finished dissections of freshly killed bees, prior to mounting them in glycerol.
For preserving material, however, many prefer Carl's solution.
This is made up of:
- 95 % alcohol 17 parts
- formalin 6 parts
- water 28 parts
- glacial acetic acid 2 parts.
The acetic acid should be added just before using, i.e. 2 parts of acetic acid to 51 parts of the remaining mixed constituents.
Larvae and pupae can be extracted from their cells without damage by floating them. This is quite easy if a jet of water from a fine nozzle is directed into the cells. They should be carefully handled, using a small spoon or section lifter, and at once put into formol alcohol or Carl's solution. They should be dissected two days later (see section 3.6.1.).