A healthy honey bee colony keeps a tight, near-solid brood pattern surrounded by bands of stored pollen and capped honey. When protein (pollen) or carbohydrate (nectar/honey) income falls short, nurse bees ration what little food they have — and the first visible sign is the brood pattern itself turning ragged and "spotty" as the queen is held back from laying and marginal larvae are abandoned or eaten.
Nutritional gaps in the brood nest are usually concentrated at the margins, correlate with a visibly thin pollen/honey band, and recover within days of feeding. Brood disease produces an irregular, scattered pattern anywhere in the nest, sunken or perforated cappings, and does not improve with feeding alone — it needs a different intervention entirely.
A single strong colony can consume 20–30 kg of pollen and well over 100 kg of honey in a year — most of it during the spring brood-rearing build-up, which is exactly when a protein shortfall does the most damage to colony strength.
A 3D brood frame lets you watch a colony's brood pattern, pollen band and honey band respond in real time as pollen and nectar reserves rise and fall — and recover as you feed the colony.
The brood nest, pollen band and honey band all thin outward-in as reserves fall, reproducing the classic "spotty brood pattern" inspectors look for, while the disease overlay shows the scattered, non-edge-following pattern typical of brood disease for comparison.
Drag the pollen and nectar sliders down to starve the colony and watch the pattern fragment, then use the pollen patty and syrup feed buttons to simulate feeding and watch the frame recover over a few seconds.
Because nurse bees ration food to the queen and larvae first, a real deficiency almost always shows up at the margins of the brood nest before it shows up in the centre — exactly the pattern reproduced here.