Low temperatures in nature occur together with desiccation conditions, causing changes in metabolic pathways and cellular dehydration, affecting hemolymph volume, water content and ion homeostasis. Although some research has been conducted on the effect of low temperature on Gromphadorhina coquereliana, showing that it can survive exposures to cold or even freezing, no one has studied the effect of cold on the hemolymph volume and the immune response of this cockroach. Here, we investigated the effect of low temperature (4 °C) on the abovementioned parameters, hemocyte morphology and total number. Cold stress affected hemocytes and the immune response, but not hemolymph volume. After stress, the number of circulating hemocytes decreased by 44.7%, but the ratio of apoptotic cells did not differ significantly between stressed and control individuals: 8.06% and 7.18%, respectively. The number of phagocyting hemocytes decreased by 16.66%, the hemocyte morphology drastically changed, and the F-actin cytoskeleton differed substantially in cold-stressed insects compared to control insects. Moreover, the surface area of the cells increased from 393.69 µm 2 in the control to 458.38 µm 2 in cold-treated animals. Together, our results show the links between cold stress and the cellular immune response, which probably results in the survival capability of this species. Abbreviations CHC Circulating hemocyte count NR Neutral red AC Anticoagulant buffer AMU Adam Mickiewicz University SR-VAD-FMK Sulforhodamine derivative of valyl alanyl aspartic acid fluoromethyl ketone WB Wash buffer THC Total hemocyte count TWC Total water content One of the key elements responsible for the evolutionary success of species is adaptation to adverse environmental conditions. Most insect species live, reproduce and survive within a limited temperature range 1. This thermal range depends on a number of elements, such as developmental stage, sex or species geographical origin, with tropical ones exhibiting a narrower temperature range than temperate 2. The geographic distribution of insects is determined by many factors, among which the ability to withstand low temperatures (cold tolerance) is one of the major factors 3. Therefore, in the course of evolution, insects living in harsh environments with low temperatures developed a set of adaptations to counteract the harmful effects of stress and to survive suboptimal thermal conditions 4-6. The cold stress response has been well documented in many species from temperate 7-9 and subarctic zones 10-12. Adaptation to cold stress and species-specific temperature limits are determined by the geographical origins and niches of insects 13,14. For instance, species from temperate zones manage cold stress better than tropical species from the same family, as was reported in flesh flies 15. Additionally, Drosophila species from the tropics are usually less tolerant to low temperatures than species from temperate regions 16-19. However, whether insects from tropical regions can survive cold stress and the mech...