Removal of small hive beetle (Aethina tumida) eggs and larvae by African honeybee colonies (Apis mellifera scutellata)

The removal of small hive beetle [SHB] eggs and larvae was studied in seven Apis mellifera scutellata colonies. Because female beetles can protect their eggs by oviposition in small cracks we introduced unprotected eggs and protected eggs into these colonies. Whereas all unprotected eggs were removed within 24 hours, 66 +/- 12% of the protected eggs remained, showing that SHB eggs are likely to hatch in infested colonies. However, all larvae introduced into the same seven colonies were rejected within 24 hours. Workers responded quickly to the presence of SHB offspring in the colonies because 72 +/- 27% of the unprotected eggs and 49 +/- 37% of the larvae were removed within the first hour after introduction. The removal of SHB eggs and larvae was not correlated with colony phenotypes (size, amount of open and sealed brood, pollen and honey stores). Our data show that African colonies remove both SHB unprotected eggs and larvae within short periods of time. Therefore, we conclude that this removal behavior plays an important role for the apparent resistance of African honeybees towards SHB infestations.