Every fact in the three bee lessons is listed here with where it comes from. The numbers in [brackets] on the lesson pages link to this list.
How we rate sources
High: space agencies (NASA), peer-reviewed open textbooks (OpenStax, Rice University) and professional scientific societies (American Physical Society).
Medium-high: reputable science news reporting directly on a primary document.
Medium: single-author essays and popular history sites. We only use these for history details, and never on their own: each one is paired with a second source.
Wikipedia was not used as a source. Numbers are rounded (for example 9.8 m/s² for Earth's gravity). The text was drafted with help from AI (Claude) and then checked against these sources. Corrections: hello@echoesof.science.
Where the facts are simplified or less certain: figures on how much food depends on pollinators measure different things: about 84% of EU crops depend on insect pollination [1], while about 35% of the world's food crops depend on animal pollinators [2]; the money values are estimates [2]. 'About 20,000 described bee species' counts known species only [4]. The waggle-dance distances in lesson 3 are one set of example values from university lecture notes, and the straight-line formula is our simple fit to those values [6]. Bees are not the only pollinators: flies, beetles, butterflies, moths, birds and bats also pollinate [1][2].
All sources
[1] Insect pollination
Natural History Museum, London · Reliability: High
Type: Natural history museum
Pollination is how flowering plants reproduce: pollen moves from the anther (male part) to the stigma (female part) so the plant can make seeds. Some plants use wind or rain, many use animals. Plants give nectar and pollen as a reward. Bumblebees vibrate to shake pollen loose (buzz pollination) and comb it into pollen baskets on their legs (corbiculae); solitary bees carry pollen on a pollen brush (scopa) on the legs or under the abdomen. The UK has nearly 250 species of solitary bees and at least 1,500 insect species that pollinate. Bumblebees can forage several kilometres from the nest; solitary bees mostly within 500 m. An estimated 84% of EU crops and most wildflowers depend on insect pollination; in a UK study insect pollination tripled apple production. Pollinators are declining; causes include climate change, habitat loss and light pollution.
U.S. Fish and Wildlife Service · Reliability: High
Type: National government wildlife agency
As much as 35% of the world's food crops depend on animal pollinators (about one in every three bites of food). Pollinators add more than $235 billion a year to the value of global crops (FAO figure). About 4,000 species of native wild bees live in the U.S. Birds, bats, butterflies, moths, flies, wasps and beetles also pollinate. Almonds, apples, blueberries, cherries, alfalfa, tomatoes and pumpkins need insect or bird pollination. More than 70 pollinator species are listed as endangered or threatened.
[3] 7 things you should know about bees and other pollinators
Smithsonian's National Zoo and Conservation Biology Institute · Reliability: High
Type: National zoo and research institute
Pollinators provide about one of every three bites of food we eat. About 20,000 plant species are buzz pollinated, including blueberries, cranberries, tomatoes and potatoes: a bumblebee lands on a flower and rapidly vibrates its thorax muscles, which shakes pollen from the anther. Some plants are wind-pollinated.
Oxford University Museum of Natural History · Reliability: High
Type: University natural history museum
There are about 20,000 described species of bees. Honeybees and bumblebees are a very small proportion; most bee species are solitary. Small bees are often mistaken for wasps or flies. Bees and flowering plants have co-evolved for over 100 million years; plants provide nectar and pollen. About 10% of bee species are parasites of other bees.
University of Florida, IFAS Extension · Reliability: High
Type: University extension publication
A honeybee colony has a queen, workers and drones. The queen is the only reproductive female and lays the colony's eggs; queens can live several years. Workers are non-reproductive females; they care for the brood, maintain and defend the hive and collect pollen and nectar, and their tasks change with age. Drones are males that mate with queens from other colonies. The brood area is kept at about 34 °C (93 °F). When a colony swarms, the queen and up to two thirds of the workers leave to found a new colony.
Texas A&M AgriLife Extension, Department of Entomology · Reliability: Medium-high
Type: University extension lecture notes
A swarm has one queen and about 10,000 workers. The round dance signals food less than about 100 m away and gives no direction. The waggle dance signals food more than about 200 m away: the angle of the waggle run gives the direction relative to the sun, and its duration gives the distance (about 13 waggles per second). Example values: 0.5 s ≈ 200 m, 1.0 s ≈ 800 m, 1.5 s ≈ 1,400 m, 2.0 s ≈ 2,000 m, 3.0 s ≈ 3,200 m. Recruits follow about 6–8 dance cycles and average them.
[7] How bees make honey (EarthDate fact sheet, episode 173)
EarthDate, Bureau of Economic Geology, The University of Texas at Austin · Reliability: Medium-high
Type: University science-outreach fact sheet
Worker bees collect nectar from flowers and pass it to hive bees, whose enzymes break sucrose into simpler sugars. The bees store it in cells and fan it to lower the water content from 50–70% to about 18–20%, then cap the cells with wax. A worker may visit up to 2,000 flowers in a day; one pound (about 0.45 kg) of honey takes visits to about 2 million flowers.
Smithsonian National Museum of Natural History · Reliability: High
Type: National natural history museum (teaching resource)
Insects have three main body parts (head, thorax and abdomen), six legs, a pair of antennae used to sense chemical signals, and either no wings or two pairs. A bee is shown as an example of an insect.