Honeybee colonies keep the brood nest temperature between 33 and 36 degrees Celsius using muscle movement to warm the hive. Bees, like many insects, are cold blooded and require their brood to remain within a small temperature range to continue normal development. Responding to temperature changes in the environment, or thermoregulation of the nest, is the job of special heater bees. If a heater bee is trying to warm an individual brood cell, it can press against the top of the cell with its thorax, or midsection, to transfer heat to the developing young inside. Similarly, bees can also crawl inside a neighboring cell to transfer heat. The current leading hypothesis says heating is accomplished using muscle contraction for periods of time up to 45 minutes. The muscles that contract are flight muscles, and decoupling the wings from these muscles separates wing movement from muscle activity that would normally initiate flight; that way, the muscles can contract without moving the wings. The heat produced from muscle contraction warms the bee’s body up to 44 degrees Celsius, about 10 degrees warmer than a normal bee. Body heat transferred to the brood cells can effectively circulate around the hive and maintain a stable temperature in the hive overall.Edit Summary
“We find that many bees that are apparently resting inside empty cells in the brood comb are participating in the regulation of brood temperature by serving as a heat source for the neighbouring, sealed, brood cells. This hitherto unrecognised thermal activity of bees inside cells is remarkable because long-duration cell visitors were previously considered to be resting and also because heat production inside cells provides a way to transfer heat to the brood more efficiently than heating via the brood caps.” (Kleinhenz et al. 2003:4218).
Hot bees in empty broodnest cells: heating from withinJournal of Experimental BiologyDecember 1, 2003
“Bees use two pairs of big fibrillar muscles, the dorsal longitudinal (DL) and the dorsoventral (DV) indirect flight muscles in various behaviours. The most important behaviours include warming of individuals in preparation for flight (Esch, 1960; Heinrich, 1980), flight itself (Esch etal. 1975; Esch 1976), communal hive heating (Himmer, 1932; Esch, 1960; Heinrich, 1987) and fanning during regulation of hive temperatures (Lindauer, 1954).” (Esch and Goller 1991:419).
“The big indirect flight muscles in the thorax of honeybees and bumblebees show two modes of action: they contract with ‘conventional’ twitches in response to slowly repeated muscle potentials and go into tetanus at higher muscle potential frequencies. They can also contract much faster when quickly stretched (stretch activation)” (Esch and Goller 1991:419).