The causative agent of larval rot and odor disease in Europe is honeycomb coccus of the hive, and the rest are secondary bacteria, such as Bacillus hive, Bacillus sidereus and its variant streptococcus of the honeybee.

Honeycomb cocci of the hive is a lance-shaped cocci, its diameter is 0.5 to 1.1 micrometers, non-motile, is Gram-positive but staining is unstable, sometimes show Gram-negative. The bacterium does not form spores and may sometimes form pods. Smear examination shows that it is mostly present as a single, but also arranged in double chains or plum blossom complexes. Streptococcus humilis grows well on potato agar medium.