Dynastine Scarab Beetle

Dynastine scarab beetles (Cyclocephala colasi) are facultative endotherms, which means they are able to maintain an abdominal temperature that is higher than their surroundings through exercise. They spend most of their adult lives inside the flowers of Philodendron solimoesense, where ambient temperature averages about 28 degrees C (82 F) due to heat generated by the flower itself (floral thermogenesis).

In French Guiana, the dynastine scarab beetle (Cyclocephala colasi) forms a close association with one member of the Araceae family, Philodendron solimoesense, a hemi-epiphyte. The inflorescence (cluster of flowers) of P. solimoesense is a spadix, a white fleshy spike of tiny flowers enclosed by an outer covering called a spathe. Each spadix includes female flowers on the lower portion and male flowers on the upper portion; a section of sterile male flowers lies in between the reproductive male and female flowers. The flowering process, and the fascinating method by which the plant achieves pollination by beetles, was documented by Marc Gibernau and colleagues (see references). The process occurs over two days in July, with inflorescences of different plants opening at slightly different times. The opening of different inflorescences on the same individual plant is separated by a few days, which likely prevents self-pollination. The spathes open in the morning of the first day, revealing the spadix. By late afternoon, the spadix becomes hot and produces a strong odor that is unpleasant to humans. Each inflorescence is visited by several C. colasi, which begin to arrive after the spadix becomes hot and odorous. At this point the beetles are already covered with pollen from another flower previously visited. They crawl around on the female flowers on the lower part of the spadix, where they find conspecifics and copulate in the floral chamber. The following day, the beetles remain in the protected floral chamber, feeding on the sterile male flowers. The spathe begins closing around the spadix, forcing the beetles to climb up - across the reproductive male flowers - and out. At the same time, the male flowers release large chains of pollen that stick to the beetles. The beetles eat some of the pollen but are still covered with it when they reach the top of the inflorescence and fly off to another, recently opened, inflorescence.