Effect of Temperature upon Energy Reserves of the Monarch Butterfly, Danaus plexippus (L.) (Lepidoptera : Danaidae)

The effects of three day temperatures (high, 36 ± 1°C; medium, 20-30°C; low, 10-18°C) on lipid accumulation and lean dry weights of monarch butterflies when night temperatures are <10°C are described. Reproductively dormant monarchs accumulated lipid when held at high or low daily temperatures. Lipid accumulated until day 15 and then diminished. Lipids were not stored at medium temperatures. Reproductively active butterflies did not store lipid. Lean dry weights of reproductively dormant monarchs pre-treated with low temperatures were higher than those of other groups. These data, together with information on other aspects of monarch winter biology, suggest that behavioural modification of body temperature is important in energy reserve storage.