Arboreal termites are widely recognized for the ecological functions of their conspicuous nests, yet their interactions with the underlying soil remain poorly understood. Here, we provide the first comprehensive characterization of the hypogeal constructions associated with the arboreal termite Constrictotermes cyphergaster and evaluate their effects on soil properties across two contrasting pedological contexts in a semiarid environment in Brazil. We documented a consistent subterranean system composed of a central chamber and radiating tunnels connected to arboreal nests by a single gallery, revealing a poorly recognized vertical extension of the colony. The architecture of these hypogeal structures was independent of arboreal nest size, suggesting a functionally regulated subterranean component. By comparing soils collected from hypogeal constructions, soil beneath nests, and surrounding soil controls, we show that termite activity modifies soil chemistry and physical structure, but in a context-dependent manner. In hydromorphic Stagnosol soils, termite constructions increased porosity and pH, and base cation concentrations, indicating effects on soil structure and biogeochemistry cycling. In nutrient-poor Regosol soils, termite influence was primarily expressed through the accumulation of organic matter and nitrogen. Across both soil classes, hypogeal chambers exhibited higher nutrient content, revealing these structures as biogeochemical hotspots. Our findings demonstrate that C. cyphergaster functions as a dual-strata ecosystem engineer, integrating arboreal and subterranean environments through a cryptic yet ecologically consequential hypogeal system. These results redefine the ecological footprint of arboreal termites and highlight their potential role in enhancing soil functioning in semiarid landscapes.

Termites are known as wood consumers, although some species eat other substrates. Assessing resource selection is important to understanding their biology. The present study provides information on the foraging behavior of Constrictotermes cyphergaster (Blattaria, Termitidae) in a dry forest area of Caatinga in Brazil. We aimed to verify the frequency of resource exploitation by termites as a function of environmental and soil temperatures. We found no significant differences in resource exploitation as a function of temperature, which is interesting because this variable is often reported as modulating foraging activity in some other termite species. This species forages on open trails at high temperatures in the Brazilian semi-arid zone. Environmental changes may affect the dynamics of their behavior and, consequently, the ecosystem, since C. cyphergaster influences the carbon cycle and can modify the soil. Our study provides a basis for future research intending to understand the adaptations of this termite to live in the drylands.

Termites are eusocial insects that maintain cohesion and exchange information through frequent physical interactions among nestmates. This social organisation underlies the principle of horizontal insecticide transfer, which is widely exploited as a termite control strategy. However, despite extensive laboratory evidence supporting its effectiveness, the specific behaviours mediating interactions between intoxicated and healthy individuals remain poorly understood. Here, we evaluate how caste‐associated social context shapes behavioural interactions between healthy nestmates and a single imidacloprid‐exposed individual in Nasutitermes corniger (Termitidae: Nasutitermitinae). We compared two biologically relevant social scenarios: worker groups interacting with an exposed worker and mixed worker–soldier groups interacting with an exposed soldier. We quantified alarm‐ and prophylaxis‐related behaviours and subsequently assessed group mortality. Our results show that antennation responses depended on the interaction between insecticide treatment and caste‐associated social context. Vibratory behaviour was more frequent in worker‐only groups, whereas trophallaxis was more frequent in mixed worker–soldier groups, independently of insecticide exposure. Grooming increased independently in mixed groups and following insecticide exposure. Mortality analyses did not provide evidence that the introduction of a single exposed individual consistently altered group‐level mortality risk. Overall, our findings indicate that termite responses to intoxicated nestmates depend on caste‐associated social context, probably reflecting both caste‐specific interaction patterns and the morphological dependence of soldiers on workers.

Termites are key ecosystem engineers whose nesting activities influence soil structure, nutrient dynamics, and microbial communities, particularly in resource-limited environments. In semiarid ecosystems, where soils are typically low in organic carbon, termite-induced modifications may help sustain belowground biological activity. Constrictotermes cyphergaster is a widespread arboreal termite in the Brazilian Caatinga whose nests maintain consistent subterranean connections with the soil, yet the microbial implications of these structures remain poorly understood. In this study, we assessed fungal abundance in soils associated with the nesting system of C. cyphergaster at two semiarid sites with contrasting precipitation regimes and soil classes. Soil samples were collected from beneath arboreal nests, from termite-built hypogeous constructions, and from surrounding soils, and fungal density was quantified using colony-forming units. Fungal abundance differed significantly among sampling points at both sites, with higher densities consistently observed in soils influenced by termite structures compared to surrounding soils. These results suggest that the nesting system of C. cyphergaster creates localized conditions that favor fungal proliferation. Our findings highlight the ecological importance of arboreal termites with subterranean connections in structuring soil microbial communities and emphasize their potential role in maintaining soil functioning in semiarid landscapes.

The ecological success of termites is closely linked to their associations with gut microbial communities, yet these interactions may also entail potential fitness costs. The effects of gut-associated bacteria on host performance remain poorly understood. Here, we experimentally assessed the effects of a gut-derived Bacillus sp. isolate on the survival and feeding behavior of workers of the termite Constrictotermes cyphergaster (Silvestri, 1901) (Termitidae: Nasutitermitinae), using the opportunistic pathogen Pseudomonas aeruginosa as a reference treatment. Workers were exposed to increasing bacterial doses, and survival analyses revealed that both bacteria induced a significant dose-dependent decline in survival. However, the Bacillus isolate caused a stronger reduction in overall survival compared to controls, whereas P. aeruginosa also reduced survival but with a comparatively weaker effect. Feeding activity was independent of dose, but exposure to Bacillus sp. significantly reduced food consumption, a pattern not observed for P. aeruginosa. These results demonstrate that a gut-derived bacterium can negatively affect host survival and feeding under experimental conditions, highlighting the importance of considering both beneficial and potentially harmful effects of host-associated microorganisms on termite fitness.