Know Your Enemy: Biological Traits of Wax Moths

Greater Wax Moth (Galleria mellonella) and Lesser Wax Moth (Achroia grisella), the most destructive lepidopteran pests in beekeeping. They go through four life stages with distinct characteristics:

Egg Stage

Oviposition: G. mellonella females infiltrate hive crevices and frame surfaces nocturnally. Each clutch has 300 to 600 pink-white eggs. Each egg is about 0.5 mm in diameter. A. grisella egg prefers hiding in the hive floor debris or pollen deposits.

Hatching Dynamics:

G. mellonella: The eggs can hatch in 3-5 days in a high temperature environment (29-35℃). At a low temperature of 18℃, the delay in hatching will extend to 30 days.

High Levels of Hideaway: The eggs are pros at hiding. Even a brood frame that seems clean may have eggs that haven't hatched yet.

Larval Stage

Early Instars: The newly hatched larvae of G. mellonella are less than 1 mm long. However, their mobility is amazing. The wax moth larvae can go up to 50 meters to a bee colony once they finish hatching.

Damage from Feeding: The larvae burrow into wax combs, consume bee larval frass, and spin silken webs ("web masses").

G. mellonella: Gregarious, 28 mm max length; 19-day cycle at 32°C vs. 5-month diapause under stress.

A. grisella: The larvae are cream-colored with a brown head. They develop faster, but they are more sensitive to changes in temperature.

The larvae of the lesser wax moth (A. grisella) are solitary by nature. They prefer to feed on the organic detritus, such as waste and debris that collects at the bottom of the honeycomb.

Pupal Stages

The greater wax moth (G. mellonella) carves distinctive, canoe-shaped cavities into wooden frames during its pupal stage. At a perfect temperature of 32°C, this phase lasts about 14 days. However, it can consume 60 days if conditions are not ideal.

The lesser wax moth (A. grisella), on the other hand, has a shorter pupal period, though we don’t have an exact time frame for it.

Adult Stages

Adult greater wax moths (G. mellonella) have a wingspan of 27–28 mm and a gray-brown color. These night-active moths lay eggs throughout their lives, which can last anywhere from 9 to 44 days.

Adult lesser wax moths (A. grisella) are smaller, with a 21 mm wingspan and a silver-gray appearance. They do not respond strongly to light (a trait called weak phototaxis) and live for 4 to 31 days.

Critical Reminder: Wax moth eggs are like hidden time bombs. Cold temperatures can delay their hatching, but they won’t wipe out the infestation in honey bee colonies. A sudden jump in temperature can trigger a massive outbreak of these moths.