Seasonal comparative lipid contents between two populations of spruce beetle, Dendroctonus rufipennis (Kirby) (Coleoptera: Curculionidae)

Spruce beetles, Dendroctonus rufipennis (Kirby) (Coleoptera: Curculionidae), experience lipid loss both while overwintering and later in their life cycle while dispersing and attacking new hosts in order to feed and reproduce. It has been suggested that differences in lipid content between univoltine and semivoltine beetles may contribute to different flight capacities and therefore differential population spread. To determine if lipid contents differ between beetle populations, larvae from Duffey Lake in southern British Columbia and Prince George in central British Columbia were lab-reared at constant 21°C or 15°C temperatures (i.e. four different population x treatment combinations). Insects from Duffey Lake had higher lipid contents than Prince George insects. Insects were then placed at 4°C for 80-days to emulate winter, after which all tested populations and temperature treatments contained less fat. Insects from Duffey Lake maintained higher lipid contents over the cold period and were both heavier and larger than Prince George insects. Insect eruptive potential may vary with beetle population under a changing climate.