Queens were isolated with moist paper towels in individual plastic shipping tubes and shipped overnight to the University of Vermont. Upon arrival, queens were individually weighed to the nearest 0.01 mg with a Mettler

Toledo microbalance (AX 205 Microbalance, Mettler-Toledo, Columbus, OH, USA) and painted with one of three different colors of Testors paint pens on the thorax. Pairs of queens differing in paint color and an equal number of single ‘control’ queens were placed into 600-mL bottles 2/3 filled with damp soil in which the queens could excavate a nest and rear brood in a seminatural soil-filled tunnel. Thirty sets of bottles were set up in check details 2011, and 36 in 2012. Division of labor could emerge as a result of multiple types of self-organization

mechanisms (Duarte et al., 2011), including agonistic social interactions (Jeanson et al., 2005). To determine whether agonistic interactions drive division of labor between queens, we quantified the extent and symmetry of aggressive behavior when queens were first introduced. All pairs of queens in both nest types were observed in groups of six nests for the first 15 min following their release into the nest. All instances of aggressive behaviors (Table 1) performed by each queen during this period were recorded. The contribution of each queen to excavation behavior was quantified by intensive observations of groups of 20 nests for 15-min intervals in which all instances of excavation behavior by each queen were noted. A subset of five nests in a set was scanned by a single observer for 3–5 s before moving to the next AZD0530 subset, resulting in approximately two scans per minute per nest over the entire 15-min interval. All observations were conducted over a period of 2 days, after which excavation behavior had ceased and the majority of nests were sealed with soil. In 2011, nests were observed for a total of 10 observation MCE公司 periods; this was increased to 15 in 2012 to better capture high-intensity excavation bouts in the first few hours following queen introduction. Colonies were

collected in week eight, when the brood in the majority of colonies contained darkening pupae and/or workers. All surviving queens, larvae, pupae and workers were counted and preserved in 95% ethanol. Any pairs in which one or both queens had died prior to collection were excluded from reproduction comparisons. To determine queen lineage identity and reproductive apportionment in paired nests, DNA was extracted from a leg or the head of each queen from both the paired and control nests, and the whole body for all brood from paired nests using a standard Chelex-100 rapid extraction protocol (Helms Cahan et al., 2006). To determine queen lineage identity, the Cox1 mitochondrial gene was amplified as described in Schwander et al.