Colony Social Organisation of Halictus confusus in Southern Ontario, with Comments on Sociality in the Subgenus H. (Seladonia)

摘要

Halictus (Seladonia) confusus Smith is one of the most common bees in North America. Classified as eusocial, its colony social organization is known only from qualitative descriptions of a population in Indiana. We studied the phenology and social behaviour of this bee in the Niagara Region of southern Ontario, using nest excavations, dissections and measurements of adult females, and pan trap samples of foraging bees to elucidate key elements of colony social organisation. The colony cycle in Niagara is typical of temperate-zone halictines, with overwintered foundresses producing a first brood of worker-sized females and a few males, followed by production of Brood 2, consisting of gynes and more males. Many Brood 1 females become reproductive: about one-quarter of Brood 1 females dissected exhibited levels of ovarian development rivalling queens. In contrast, only about one-quarter of Brood 1 females become classically altruistic, sterile workers. High rates of worker reproductivity may result from early queen mortality and supersedure or from the inability of viable queens to control worker behaviour - the average queen-worker size difference was only 5.6%, and queens were not always larger than the workers in their own nests. Comparisons withthe Indiana population suggest a geographic component to variation in colony social organisation. Comparisons with other members of the subgenus for which detailed information is available, suggest that in Seladonia, as in other eusocial halictines, queen control of worker behaviour depends on the ability of queens to dominate small numbers of small-bodied workers.