“…This theory originally rested on indirect evidence, including observations that queens and workers apparently always differ in their CHC profiles (reviewed in Van Oystaeyen et al, 2014), that CHC profiles correlate with inter-individual variation in fecundity within a given caste (e.g., D’Ettorre et al, 2004; Holman, Dreier & D’Ettorre, 2010), and that workers can discriminate between the CHCs of fertile and non-fertile individuals (Dietemann et al, 2003; D’Ettorre et al, 2004). Recently, studies using synthetic hydrocarbons have experimentally demonstrated that queen-like CHCs affect worker ovarian development (in seven species; Van Oystaeyen et al, 2014; Holman et al, 2010; Holman, Lanfear & D’Ettorre, 2013; Holman, Hanley & Millar, 2016; Holman, 2014; De Narbonne et al, 2016; Oi et al, 2016), and/or induce behavioural changes in workers that are putatively related to reproduction (in three species; Holman et al, 2010; De Narbonne et al, 2016; Smith, Millar & Suarez, 2015; Smith, Hölldobler & Liebig, 2009). A recent comparative analysis of chemicals thought to be correlated with caste or fertility in 64 species of social Hymenoptera concluded that these chemicals were most commonly saturated CHCs, and that the correlation between saturated CHCs and female fecundity appears to be ancestral in Hymenoptera (Van Oystaeyen et al, 2014).…”