Survivorship Curves and Longevity for Workers of Bombus ardens SMITH and Bombus diversus SMITH (Hymenoptera, Apidae)

Survivorship curves and longevity of workers were observed on 2 species of Japanese bumblebees, Bombus (Pyrobombus) ardens SMITH and B. (Diversobombus) diversus SMITH. In both species, the survivorship curve of specialized foragers markedly differed from that of house bees. The curves of whole workers and specialized foragers steeply dropped in early adult life, while the curve of house bees plus occasional foragers slowly descended step by step. Foraging was started from 3 days after emergence and the number of foragers was generally large during 4 to 16 days after emergence when the survival rate of workers rapidly decreased. The average longevities for whole workers, foragers, and house bees plus occasional foragers in a favorably developing and queenright colony were 26.3, 15.6 and 42.8 days in B. ardens and 19.4, 12.4 and 35.0 days in B. diversus.