Honey Stomach (Crop)

A Living Transport Tank

The honey stomach (also called the crop or ingluvies) is an expandable sac in the anterior (front) portion of the bee's digestive tract, located between the esophagus and the proventriculus (a valve that connects to the true digestive stomach). When a forager collects nectar from flowers, she stores it in the honey stomach rather than her digestive stomach. The proventriculus acts as a one-way valve, allowing the bee to choose whether to pass the nectar backward into her own digestive system (for personal nutrition) or forward through her mouth (for delivery to the hive).

Capacity and Transport

The honey stomach can expand to hold approximately 40 milligrams of nectar, nearly equal to the bee's own body weight. A forager returning to the hive with a full honey stomach is noticeably heavy and slow compared to her outbound flight. She may visit 50 to 100 flowers to fill her crop on a single foraging trip, and she will make 10 to 12 trips per day during peak nectar flow.

Enzymatic Processing Begins Here

The conversion of nectar to honey begins inside the honey stomach. The enzyme invertase, secreted by the bee's hypopharyngeal glands and mixed with the nectar during collection, begins breaking down sucrose into glucose and fructose during the flight home. Glucose oxidase is also added, which will later produce hydrogen peroxide (one of honey's antimicrobial agents) when the honey is diluted. By the time the forager returns to the hive, the nectar's chemistry has already begun changing from raw plant sugar to the complex mixture that will become honey.