Size change of Apis mellifera eggs during the Incubation period
Nine queen honey bees (Apis mellifera) were restricted for 4 h 30 min under a queen-excluder cap on an empty comb in the centre of the broodnest. 25 eggs were removed from each comb and their length and width were measured, as well as the length of the embryo. The egg removal and measurements were repeated every 7 h 30 min. In total, 2475 eggs were measured, on which 7425 measurements were made. In addition, groups of 25 eggs were weighed in four determined periods. Results showed that the length, width and volume of eggs 7 h 30 min-12 h old reduced to 98%, 98% and 94% of their initial dimensions, respectively. Eggs 15-19 h 30 min old increased the three dimensions to 99%, 98% and 96%, respectively. Next the eggs decreased to 91%, 90% and 73% at the age of 52 h 30 min-57 h. Subsequently a peculiar phenomenon occurred, namely the eggs increased to 93%, 92% and 78% at the time of hatching. The embryo changed its length similarly to the egg. The correlation coefficient between the length of embryo and egg was r = 0.92. The weight of eggs decreased continuously to 65% of their initial value at the hatching time. Thus, the eggs change their size and weight during the whole incubation period. It is suggested that the size and weight changes of eggs are due to metabolic processes.