Fuel uptake, storage and use in male bumble beesBombus terrestris L.

Abstract

1. During a period of more than ten days the flight activity of male bumble beesBombus terrestris follows a constant daily rhythm and they exhibit a constant pattern of large daily food (sugar) intake. The fate of the sugar consumed was studied with especial regard to the following questions: Is it converted into other storage products and, if so, in which organs are they stored? 2. Individual bumble bees were examined at three different times during the daily activity pattern (just before the onset of flight, at the beginning of foraging and at the end of the light period) and the total contents of glucose, fructose, trehalose, sucrose, glycogen and lipid in the thorax, digestive tract and the abdomen (minus digestive tract) measured. 3. No storage of glycogen or lipids was found in the male bumble bees. They store the chemical energy in the form of non-polymeric carbohydrates in the digestive tract. 4. The rates of fuel utilization during the different phases of the daily activity pattern were calculated. For the first time, the sugar consumption rate in male bumble bees during flight was determined directly (7.6 μmoles hexose units/min·g body mass). 5. A 24-h energy budget for male bumble bees was constructed from measurements of daily food uptake and the rates of energy consumption (Table 3).