Insect behavioral restraint and adaptation strategies under heat stress: An inclusive review

In fluctuating thermal conditions, the survival challenge for insects is particularly difficult because their physiological activities depend upon environmental temperature. The extreme temperature or heat stress leads to the insect species' extinction and evolution in adaptation strategies. Upon extreme heat, many insect species cannot survive, because they do not possess sufficient heat tolerance during gradual heat stress in their habitat. In the current review, we demonstrated the physiological process which triggers responses toward heat stressed environments and engenders the heat tolerance capacities in ectothermic insects including the nervous system response to detect heat, metabolic mechanism in response to heat stress, silk shelters behavior during thermal changes, host plant preferences, microhabitat selection, thermoregulatory behavior and thermal acclimation response under the heat stress. This review highlighted that besides the insect’s responses regulated by varied physiological mechanisms, heat shock proteins (HSPs) still needs proper investigations. Entrenched in geographical distributions and microhabitat selection, we discussed the adaptation strategies and physiological and behavioral mechanisms that evolved due to heat stress. Many insect species cope with heat stress with the help of phenotype plasticity and genetic variations. The plasticity mechanisms are not sufficient alone to avoid extreme temperatures in insect populations. There is still need to explore how insects respond to thermal changes by using advanced genetic variation methods in both hot and cold-adapted insect species. This review enriched the new insight to improve the researcher’s understanding of distinct responses and evolutionary consequences of insect responses and thermal adaptations under the changing climate.