J Appl Entomol. 2019;1–13. wileyonlinelibrary.com/journal/jen | 1 © 2019 Blackwell Verlag GmbH 1 | INTRODUCTION The greater wax moth (GWM), Galleria mellonella L. (Lepidoptera: Pyralidae), is considered as one of the destructive pest of bee‐ hive products, especially the stored comb (Jafari, Goldasteh, & Afrogheh, 2010; Nielsen & Brister, 1979). The impact of its dam‐ age is more severe in the tropics and sub‐tropics due to their warm climate which increases the reproductive potential (with females capable of laying up to 300 eggs in <3 weeks which develop rap‐ idly) and infestations by the moths (Shimanuki, Knox, Furgala, Caron, & Williams, 1992; Williams, 1997), (Nielsen & Brister, 1977; Shimanuki et al., 1992; Warren & Huddleston, 1962). The larva feeds on hive components, preferably in the order of pollen, wax, honey, occasionally brood, and cast‐off honeybee pupal skins, and creates tunnels as they burrow into the midrib of the comb leaving masses of webs (Dweck, Svensson, Gündüz, & Anderbrant, 2010; Shimanuki et al., 1992; Smith, 1965; Türker, Togan, Ergezen, & Özer, 1993; Williams, 1997), frass and debris on the frame (Williams, 1997). Honeybee colonies weakened by pesticide contamination, pathogens and diseases (Romel, Scott‐Dupree, & Carter, 1992), or undergoing starvation or with low adult populations (Shimanuki et al., 1992) are particularly vulnerable to moth infestations. Moth infestations often lead to galleriasis (trapping of emerging bees by silken threads spun by the GWM larvae) (Williams, 1997), Received: 10 September 2018 | Revised: 28 December 2018 | Accepted: 18 January 2019 DOI: 10.1111/jen.12617 ORIGINAL CONTRIBUTION Decanal as a major component of larval aggregation pheromone of the greater wax moth, Galleria mellonella Charles A. Kwadha 1,2 | Jacqueline M. Mutunga 1 | Janet Irungu 1 | George Ongamo 2 | Paul Ndegwa 2 | Suresh Raina 1 | Ayuka T. Fombong 1 1 International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya 2 School of Biological Sciences, University of Nairobi, Nairobi, Kenya Correspondence Charles A. Kwadha and Ayuka T. Fombong, International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya. Emails: ckwadha@gmail.com; fpalais@gmail. com Present Address Charles A. Kwadha, Swedish University of Agricultural Sciences, Alnarp, Sweden Funding information European Union, Grant/Award Number: DCI‐FOOD‐2011/023‐520; UK Aid from the UK Government; Swedish International Development Cooperation Agency (Sida); Swiss Agency for Development and Cooperation (SDC); Kenyan Government Abstract Larvae of the greater wax moth (GWM), Galleria mellonella, a destructive pest of the honeybee ( Apis mellifera), have been observed to display aggregation behaviours. However, the underlying mechanism by which these larvae come together remains unknown. We hypothesized that the GWM larvae detect, orient towards and utilize conspecific larval chemical cues to aggregate in groups. We used dual‐choice olfac‐ tometer assays to investigate the involvement of conspecific larval odours in their aggregation amongst 3–5th instar and 8th instar larvae. The assays revealed that only 8th instar larvae were significantly attracted to their odours and those emanating from newly spun cocoons. Coupled gas chromatography–mass spectrometry (GC‐ MS) of larval head space odours analysis revealed the presence of four compounds: nonanal, decanal, tridecane and tetradecane in pupal and mature larval odour ex‐ tracts. However, using synthetic compounds, behavioural assays showed that only decanal induced significant attraction, therefore, suggesting its role as a major com‐ ponent of the larval aggregation pheromone of GWM. Our findings reveal the in‐ volvement of volatile organic compounds in the aggregation behaviour of mature wax moth larvae and thereby offer prospects for the development of an odour‐baited in‐hive trapping management tool for wax moth larva. KEYWORDS GC‐MS, honeybee pest, olfactometer, pyralidae, semiochemical