Material and methods
We recorded opportunistic observations of cannibalism in odonates during field work in India, Bangladesh, and Australia during 2014 to 2024 (Fig 1 a-f). We further collated records of cannibalism from 18 published literatures (Fraser, 1934; Corbet, 1962; Bick & Bick, 1963; Bick & Sulzbach, 1966; Müller, 1972; Martens & Smeyer, 1978; Utzeri, 1980; Robinson, 1983; Robertson, 1985; Fincke, 1987; Dunkle, 1990; Cordero, 1992; Rolff & Kröger, 1997; Reels, 2010; Nair, 2011; Kosterin & Chartier, 2017; Payra, 2020; Priyadarshana, 2021) , peer-reviewed web portals (http://www.odobd.org, https://www.indianodonata.org) (Shah & Khan, 2020; Joshi et al., 2022), and observation of community scientists in online platform https://www.inaturalist.org/, and taxonomy focused social media group (http://www.facebook.com/groups/OdoBD).
After accumulation of photographic records and observations, we identified the species, life stages (adult, immature, and teneral), and sexes (male, female) of the involved individuals by using taxonomic keys of Fraser (1933, 1934, 1936), Abbott (2015), Boudot et al.(2021) and peer-reviewed websites (http://www.odobd.org and www.indianodonata.org) (Shah & Khan, 2020; Joshi et al., 2022). Based on the life stage and sex involved individuals were categorized as Mature Male (m♂), Mature Female (m♀), Young Male (y♂), Young Female (y♀), Teneral Male (t♂), and Teneral Female (T♀). Body size (average length of abdomen including appendages) of involved males and females in cannibalism was obtained from Fraser (1929, 1933, 1934, 1936); Rodrílguez et al. (2015); Boudot et al. (2021) and the website (http://www.odobd.org ). We applied DurgaDiff function of Durga R package v2.0 (Khan & McLean, 2024) to determine if there is difference of body size between predator and prey of individuals involved in cannibalism. The likely mechanisms of cannibalism in adult odonates were categorized in three categoriesviz ., Female driven cannibalism (Females cannibalizing males), male driven cannibalism (males cannibalizing females), intrasexual cannibalism (when males devouring males and females devouring females). We used 63 (28 Anisoptera and 35 Zygoptera) out of 83 observations where we could identify the sexes based on the photographs and literature, to determine the involvement of the sex in cannibalism. Further to ascertain the involvement of life stages in cannibalism we choose 73 instances (30 Anisoptera and 43 Zygoptera) where we were able to identified the life stages confidently. Instances where we could not identify age or sexes correctly were removed from the final analysis.