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.

Insects exhibit diverse colours that play a crucial role in communication that directs inter- and intra-species interactions such as predator-prey interactions and sexual selection. Anthropogenic climate change may impact insects colour expression and consequently their physiology and behaviour. Insects can respond to changing climatic through phenotypic plasticity or genetic modification, however it is unclear how any of the resulting changes in body and wing colour may impact interactions with conspecifics and heterospecific (e.g., predator, prey, and mate). The aim of this review is to synthesis the current knowledge of the consequences of climate driven colour change on insects. Firstly, we discussed the environmental factors that affect insect colours, and then we outlined the adaptive mechanisms in terms of phenotypic plasticity and microevolutionary response. Secondly, we conducted a systematic review and performed a qualitative analysis to understand how experimental rearing temperature influences insect colouration. Finally, we gave an overview of the beneficial or maladaptive impact of colour change on sexual selection. We concluded by identifying research gaps and highlight potential future research areas.