Internal temperature comes from a simple steady-state thermal balance: colony metabolic heat output divided by total heat conductance, where conductance is the sum of a wall term (from material R-value and thickness) and a ventilation term (from the vent opening fraction):
R = material.R × thickness
G_wall = 1 / R
G_vent = 0.12 + 2.6 × (vent / 100)
T_in = T_out + Q_bees / (G_wall + G_vent)
Thicker walls and higher-R materials (polystyrene) raise the internal temperature above ambient; thin walls, low-R materials (mesh, cob) or wide-open vents let it drift toward the outside temperature. The bee cluster contracts into a tight ball when cold and spreads out — fanning near the entrance — when hot; rising particles show convective airflow, faster with a bigger vent and a bigger inside/outside gap.
- Shell tint — cool blue when the hive runs near ambient, warm orange when heat is being retained well above it.
- Cluster dots — bee positions inside the comb region; radius tracks the clustering factor derived from internal temperature.
- Flow dots — convection particles rising from the bottom vent to the top vent.