ReadMe for Queen colony initiation data set from Baron, G.L., Jansen, V.A.A., Brown, M.J.F., Raine N.E. 2017. Pesticide reduces bumblebee colony initiation and increases probability of population extinction, Nature Ecology and Evolution: in press. This ReadMe file describes the data file accompanying the experimental section of the above publication, where full details of the methods and experimental set up can be found. This manuscript should be cited when using these data. The following files are included: 1) Filename: ÒBaron etal 2017 QueenData.xlsxÓ Data collected during laboratory trails using Bombus terrestris queens. Column headings are as follows: * ID: unique identification number for each queen included in the final experiment * Queen Colony: the number code relating to the colony from which each queen was reared * Male Colony: the number code relating to the colony from which the male each queen mated with was reared * Hibernation: the duration of hibernation each queen underwent (short = 6 weeks, long = 12 weeks) * Pesticide: Pesticide treatment (PEST = queen received the pesticide treatment, NOPEST = control, queen did not receive the pesticide treatment) * Parasite: Parasite treatment (PARA = queen was exposed to the parasite, NOPARA = control, queen was not exposed to the parasite) * Infection Status: infection status after faecal checks * Thorax width (mm): thorax width of queen, measured in mm * Percentage weight lost during hibernation: percentage of queen mass at start of hibernation lost during the hibernation period (%) * Survival: whether the queen survived to the end of the ten week experiment * Survival time: time from emergence from hibernation until death (days) * Eggs laid: whether the queen laid eggs within the ten week experiment * Time to egg laying: time after emergence from hibernation until egg laying (days) * Average daily syrup consumption: amount of pesticide, or control, treated syrup consumed during the pesticide treatment phase of the experiment per day (ml) * Adult workers reared: whether or not the queen reared adult workers * Number adult workers reared: number of workers produced by end of the 14 week experiment * Time to adult workers: time from emergence from hibernation to first adult worker emergence (days)