Ten workers from each size morph were obtained from five different colonies, resulting in fifty individuals per size morph, which were kept at -80C in RNAlater [Sigma-Aldrich] upon sampling. The antennae were removed from the body and were pooled separately for small, medium and large individuals of each colony (i.e. ten individuals per pool, or twenty antennae per pool), resulting in five replicates per size morph. RNA was extracted from these pools using the RNEasy Plus Mini Kit, including DNase I digestion, according to manufacturers instructions [Qiagen, Hilden, Germany]. Samples were sent to Novogene (Cambridge) for Illumina paired end sequencing at a read length of 150 base pairs. Samples were sequenced to an average depth of 47.9 million read pairs (s.d.= 2.8M).