A bee's body plan is inside-out compared with ours: the main nerve cord runs along the belly (ventral), not the back, as a chain of ganglia — mini brains that control their own body segment even if disconnected from the head.
Its circulatory system is open: a single muscular dorsal-vessel "heart" pumps straw-coloured hemolymph forward, but the fluid then spills directly into the body cavity and bathes the organs rather than flowing through veins and arteries.
Oxygen never travels in the blood at all — pairs of valved spiracles along the body wall open into branching tracheal tubes that carry air straight to every tissue, driven by abdominal pumping ("ventilation").
Nerve impulses in insects are unmyelinated, so conduction is slower than in vertebrates and speeds up as flight muscles warm the thorax — press Stimulate nerve at each activity level to see the conduction time drop from a resting bee to one mid-flight.
- Body outline — fades the exterior silhouette so the organs stand out.
- Activity level — sets heart rate, ventilation rate and nerve conduction speed together, the way a warmer, harder-working bee actually behaves.
- System toggles — isolate the nervous, circulatory, respiratory or digestive system.
- Click an organ — brain, ganglia, heart chambers, trachea/spiracles or the gut — for a short explanation of what it does.