Females cannibalizing males
In this study, we recorded frequent occurrence of females predating on
conspecific males. We found 12 (42.9%) cases in Anisoptera represented
by species Erythemis simplicicollis (9 cases) and Orthetrum
sabina (3 cases). In Zygoptera 19 cases (50%) were observed in nine
species (Agriocnemis femina , Ceriagrion coromandelianum ,Coenagrion puella , Ischnura sp, Ischnura elegans ,Ischnura graellsii , Ischnura ramburii , Ischnura
verticalis , and Lestes alacer ) where females predate on males
(Supplementary Table 1-3, Fig. 2). The predation of male odonates by
females odonates can be an act of sexual cannibalism Cordero (1992).
Sexual cannibalism (eating of male by female) has been shown in other
insect system such as spiders, and praying mantis where consuming males
has been shown to benefit fitness of the species (Nishimura & Isoda,
2004; Mitchell & Walls, 2008; Segoli et al., 2008). However, further
experimental studies are required in case of odonates to determine
fitness cost and benefit for the species. Sexual cannibalism is common
in many arthropod species and several hypotheses have been proposed by
researchers to explain the drivers that induce the sexual cannibalism
(Nishimura & Isoda, 2004; Mitchell & Walls, 2008; Segoli et al.,
2008). Females predate on males during low food availability when male
are easy to consume (Newman & Elgar, 1991). As a result of extreme mate
choice, females’ prey on undesirable rejected males (Elgar & Nash,
1988). Failed to recognize conspecific males could lead to the
consumption of males (Gould, 1984). It occurs due to the inheritance of
high aggressiveness in females (Arnqvist & Henriksson, 1997; Schneider & Elgar, 2002). Sexual cannibalism also represents male
monogamy, as in some spider species males initiate the cannibalism
process by placing their abdomen in front of female mouthparts during
copulation and sacrificing themselves to females to gain reproductive
success (Segoli et al., 2008). In Odonates, mating harassment is a
common phenomenon and costly for female fitness. Traits such as
conspicuous colour and cryptic behavior have evolved in species to avoid
male mating harassment (Khan, 2019). Simultaneously, the wheel position
and male sperm translocation have been evolved in odonates to avoid
sexual cannibalism (Rivas-Torres, 2019). Female predation on males can
be an evolutionary strategy to avoid male mating harassment (Fincke
1987; Xu & Fincke, 2022). To avoid sexual cannibalism the future
studies should focus to determine what drives female odonates predate on
male odonates.