Proboscis Lengths and Flower Utilization of Bumblebees from Sumatra and Java

We studied intra- and interspecific variations in body size and tongue dimensions of two bumblebees, Bombus rufipes and B. senex which occurred in highlands of Sumatra and Java, Indonesia. The presence/absence of B. senex which occurred only in Sumatra seemed not to affect between-island variation in tongue-morphology of B. rufipes which occurred on both islands. Although the ranges of body size (head width) overlapped between the species, Bombus senex had longer proboscis relative to head width and more elongated malar area than B. rufipes. Bombus rufipes visited various flowers both outside and inside the mountain forests, whereas B. senex was confined to mountain primary forests. Compared with temperate bumblebee communities in Japan, Europe and North America, the Indonesian community had only medium mean proboscis lengths. However, the individual variations in body size and proboscis length in Indonesian bumblebees were markedly large, associated with disproportionately enlarged queen/worker sizes.