4.4. Preparation and storage of diets

  • Estimate the needed amount of diet
  • Prepare or thaw sugar solutions (w/v)
  • Mix sugar solutions with royal jelly 1:1 (w/w)
  • Warm diet to 34.5°C in the incubator--> Section 5.9. Feeding of diets
  • Dump remaining diet or store diet maximum 2 days at 4°C

Most artificial diets for honey bee larvae contain royal jelly plus 3-9 % (w/v) each of glucose and fructose and 0-2 % (w/v) yeast extract (Rembold and Lackner, 1981; Vandenberg and Shimanuki, 1987; Peng et al., 1992; Aupinel et al., 2005; Genersch et al., 2005).

As an example, we present a detailed preparation description for 10 g diet with 6 % (w/v) glucose, 6 % (w/v) fructose and 1 % (w/v) yeast extract (diet A which is fed to larvae on day one according to Aupinel et al., 2005): 1.2 g of glucose, 1.2 g of fructose and 0.2 g of yeast extract are weighed (w) and solved in about 5 ml autoclaved water. This clear solution is filled up to exactly 10 ml (v). For preparing the final diet the aqueous solution must be mixed with fresh royal jelly 1:1 (w/w), for the given example 5 g of each are needed. If frozen royal jelly is used it can be recommended to freeze it in aliquots (e.g. amounts used to feed one plate), ready to be filled up with the same weight (w) of aqueous solution. To optimize worker rearing and avoid intercastes composition of diets and amounts of food must be changed in later larval stages (Table 2).

In another recipe (Genersch et al., 2005; 2006), the larval diet consists of 3 % (w/v) glucose, 3 % (w/v) fructose, and 66.6 % (v/v) royal jelly in sterile, double-distilled water. It is recommended to have a glucose/fructose stock solution containing 9 % (w/v) glucose and 9 % (w/v) fructose solved in sterile double-distilled water and stored at 4°C until use. Aliquots of royal jelly are stored frozen at -20°C. Every day fresh larval diet is prepared by thawing royal jelly shortly before use and mixing two volume parts of royal jelly with one volume part of glucose/fructose stock solution to obtain the above given concentrations. If an aqueous solution of yeast extract is also added, the concentration of the glucose/fructose stock solution needs to be adjusted to ensure that the larval diet does not contain less than 66.6 % (v/v) royal jelly and not more than 33.3 % (v/v) aqueous solutions. Otherwise the larval diet will contain too much water and young larvae will tend to drown in the diet or will have problems with digestion.

If investigations start in early spring, no fresh royal jelly will be available; therefore frozen royal jelly has to be used. Also, freeze-dried royal jelly stored at -70°C can be used (Peng et al., 1992). In general, we suggest preparing new diet every day or using prepared and refrigerated diets within three days. Re-freezing should be avoided.

 

Table 2. Daily amounts and composition for limited feeding according to the age of worker larvae in percentage of weight (Aupinel et al., 2005). For details on preparation of diets (w/v and w/w in particular) see section 5.4.

Day of feeding

Amount [µl]

% D glucose

% D fructose

% yeast extract

% royal jelly

1

10

6

6

1

50

2

10

6

6

1

50

3

20

7.5

7.5

1.5

50

4

30

9

9

2

50

5

40

9

9

2

50

6

50

9

9

2

50