Cannibalism in adult odonates (dragonflies and damselflies): an
intriguing but unexplored behavior
Abstract
Several insect groups exhibit the phenomenon of cannibalism, preying
upon individuals of the same species. Cannibalism is an intriguing
behavior but often poorly understood. Cannibalism is thought to be
influenced by the sex, life history stage, and physiological condition
as well as ecological and social contexts in which it occurs. Here we
review cannibalism in a carnivorous insect order Odonata (dragonflies
and damselflies), on the adult stage of their life cycles, based on
primary and secondary data. We collected primary data from our field
work (mostly from opportunistic observation) spanning eight years from
three countries (India, Bangladesh and Australia) and secondary data
including published literature and observations from global citizen
science portals. In total, we retrieved 86 instances of cannibalism and
metadata (developmental stage and sex of the individuals involved in
cannibalism) of 63 cannibalistic instances. We found that, Odonata
families with most reported cannibalism cases were Coenagrionidae (n=50)
and Libellulidae (n=31) followed by Lestidae (n=2), Aeshnidae,
Calopterygidae and Euphaediae each with one example. We classified the
cannibalism in odonates into four patterns, 1) Females cannibalizing
males, 2) males cannibalizing females, 3) intrasexual cannibalism and,
4) mature individuals cannibalizing tenerals. We found, female
cannibalizing males was higher in proportions, compared to males
cannibalizing females, and intrasexual cannibalism. We further found
that, individuals involved in Anisopteran cannibalism were mostly
matures, but in case of Zygoptera, mostly matures individuals were
canabilising tenerals. We discuss that species recognition errors,
intrasexual competition for mating, and mating harassment avoiding
strategies are major driving factors of cannibalism in odonates. We
provide a comprehensive insight into the cannibalistic behavior of adult
odonates and highlight that experimental evidences are required to
understand the mechanisms of cannibalism.