hamuli

Hamuli is the plural of hamulus, a term used in biology to denote small hook-like projections. The word can refer to two related but distinct structures in different groups of animals: feather microstructure in birds and wing coupling hooks in many insects.

In birds, hamuli are tiny hooklets along the barbules of flight feathers. These hooks interlock with neighboring barbules to hold the feather vane together, creating a continuous, aerodynamic surface. This microstructure helps maintain feather alignment and waterproofing during flight and is most evident in the primary and secondary wing feathers. The pattern and strength of hamuli can vary among species, reflecting adaptations to different modes of flight.

In insects, particularly Hymenoptera such as bees, wasps, and ants, hamuli are a row of hooks on the leading edge of the hind wing. These hooks engage with a corresponding row on the fore wing to couple the two wings during flight, allowing them to beat synchronously as a single flight unit. This wing-coupling mechanism enhances aerodynamic efficiency and maneuverability. The presence, size, and arrangement of hamuli can differ among taxa and may be used in taxonomic and functional studies.

Etymology traces both uses to the Latin hamulus, a diminutive of hamus, meaning little hook. While the general idea is the same—a hooked projection used to join or stabilize structures—the specific anatomical context distinguishes avian feathery hamuli from insect wing-coupling hamuli.