The
heat index, which combines temperature and relative humidity, plays a critical
role in influencing the survival, behavior, and development of insect species,
particularly those with economic significance such as Tribolium castaneum
(Herbst) (Coleoptera: Tenebrionidae). This study explores the impact of heat
index acclimation on the physiological processes, behavioral patterns, and
developmental dynamics of T. castaneum. The experiment exposed adult
beetles to five different heat index conditions (28°C/60%, 30°C/60%, 35°C/70%,
40°C/80%, and 45°C/90%) and measured key parameters such as metabolic rate,
critical thermal maximum (CTmax), activity levels, developmental time, and
survival rates.
The results reveal that heat stress significantly alters metabolic
activity, with oxygen consumption increasing by up to 96.9% under extreme heat
index conditions. Acclimation moderately enhanced thermal tolerance, as reflected
in an increased CTmax, but this effect diminished at extreme heat indices
(≥40°C/80%). Behavioral patterns, measured by activity levels, showed a marked
decline with increasing heat index, with acclimated beetles maintaining
slightly higher activity than non-acclimated counterparts. Developmental
dynamics were also disrupted, with prolonged developmental times and increased
mortality rates observed at higher heat indices, particularly at 45°C/90%,
where mortality reached 18%. Acclimation improved survival rates under heat
stress, but the benefits were limited under extreme conditions. These findings
suggest that while acclimation may partially mitigate the negative effects of
heat stress, the physiological and developmental limits of T. castaneum
are surpassed under extreme heat index conditions. This study underscores the
need to consider thermal adaptation and heat stress management in pest control
strategies, particularly in the context of climate change and increasing global
temperatures.
