2.5.4. Recognising the age of larvae

When queen caging is not an option to obtain larvae of known age, the age of worker larvae can be assessed visually or by weighing. Visual recognition can be done based on Fig. 7. This however, only allows for a rough estimate of age. Because the growth is exponential, visual estimation of age is error prone. A more accurate way is to weigh the larvae after having cleaned them from jelly residues and absorbed the excess water from their surface. Table 5 gives equations that allow the calculation of larva age for workers, queens and drones. Given the exponential growth of larvae, Thrashyvoulou and Benton (1982) divided the larval development of honey bees of Italian origin in several phases that could be described with regression equations for workers, queens and drones (Tables 9 and 10). The high coefficient of correlations obtained (between 92.3 and 99.7) shows that their formulas are reliable for the population measured. An equation was also produced to describe the complete development, but with lower precision and is therefore not given here (coefficient of correlations between 81.7 and 90.6). Despite the good fit of these equations, deviations might occur according to variations between bee populations and subspecies and they should be recalculated for different populations or subspecies.

Fig. 7. Development of a worker larva, starting from egg-laying by the queen. A rough assessment of larva age can be obtained by observing the space occupied by the larva in the cell. Larval instars are represented by greyed areas. Photo: V Dietemann.

figure07

Table 9. Regression equations for weight categories of honey bee workers and queens. X designate age and Y the measured weight within the category given in the second column (after Thrashyvoulou and Benton, 1965).

 

Workers

Queens

Age (h)

Weight (mg)

Regression equation

Weight (mg)

Regression equation

6 – 30

0.20 – 0.80

X = (Y - 1.41) / 32.60

0.12 – 0.69

X = (Y – 4.79) / 51.40

31 – 54

0.81 – 7.00

X = (Y – 31.90) / 2.71

0.70 – 8.50

X = (Y – 33.50) / 3.29

55 – 90

7.10 – 46.00

X = (Y – 50.60) / 0.87

8.60 – 37.90

X = (Y – 48.80) / 1.12

91 – 120

46.10 – 140.00

X = (Y – 73.30) / 1.69

38.00 – 186.00

X = (Y – 85.10) / 0.16


Table 10.
Regression equations for weight categories of honey bee drones. X designate age in hours and Y the measured weight in mg within the category given in the second column (after Thrashyvoulou and Benton, 1965).

Age (h)

weight (mg)

regression equation

9 – 54

0.29 – 3.50

X = (Y – 8.82) / 11.60

55 – 98

3.51 – 42.00

X = (Y – 52.80) / 1.09

99 – 120

42.10 – 129.00

X = (Y – 64.30) / 0.47

121 – 163

129.42 – 311.54

X = (Y – 91.6) / 0.23