Total charge acquired= +20 pC = 20*10^-12 C

Since the honeybee was neutral before, the total charge acquired would be equal to n*charge of electron, where n is number of electrons lost

charge on each electron = 1.6*10^-19 C

n*1.6*10^-19 = 20*10^-12

n=12.5*10⁷

Number of electrons lost = 12.5*10⁷