Parasites and their hosts use different strategies to overcome the defenses of the other, often resulting in an evolutionary arms race. Limited animal studies have explored the differential responses of hosts when challenged by differential parasite loads and different developmental stages of a parasite. The fungus-growing ant Trachymyrmex sp. 10 employs three different hygienic strategies to control fungal pathogens: Grooming the antibiotic-producing metapleural glands (MGs) and planting or weeding their mutualistic fungal crop. By inoculating Trachymyrmex colonies with different parasite concentrations (Metarhizium) or stages (germinated conidia or ungermianted conidia of Metarhizium and Escovopsis), we tested whether ants modulate and change hygienic strategies depending on the nature of the parasite challenge. There was no effect of the concentration of parasite on the frequencies of the defensive behaviors, indicating that the ants did not change defensive strategy according to the level of threat. However, when challenged with conidia of Escovopsis sp. and Metarhizium brunneum that were germinated or not-germinated, the ants adjusted their thygienic behavior to fungal planting and MG grooming behaviors using strategies depending on the conidia germination status. Our study suggests that fungus-growing ants can adjust the use of hygienic strategies based on the nature of the parasites.

Recent reports of insect decline have raised concerns regarding population responses of ecologically important groups, such as insect pollinators. Additionally, how population trends vary across pollinator taxonomic groups and degree of specialization is unclear. Here, we analyse 14 years of abundance data (2009–2022) for 38 species of native insect pollinators, including a range of Coleoptera, Lepidoptera and Hymenoptera specialists and generalists from the tropical rainforest of Barro Colorado Island, Panama. We estimated population trends across taxonomic groups to determine whether specialist species with a narrower range of interacting mutualistic partners are experiencing steeper population declines under environmental change. We also examined the relationship between climate variables and pollinator abundance over time to determine whether differences in sensitivity to climate predict differences in population trends among pollinator species. Our analyses indicated that most pollinator populations were stable or increasing, with few species showing evidence of decline, regardless of their degree of specialization. Differences in climate sensitivity varied among pollinator species but were not associated with population trends, suggesting other environmental factors at play for tropical insect pollinators. These results highlight the need for long-term population data from diverse tropical taxa to better assess the environmental determinants of insect pollinator trends.

Social insects employ diverse strategies, including individual and collective sanitary care as well as colony-level hygiene, to prevent, manage and control pathogen transmission. The immune system constitutes a key component of the individual defensive repertoire, but its activation entails trade-offs with other life history traits due to its high metabolic cost. In this study, we investigated how different immune strategies interact in social insects. We challenged workers of the leaf-cutting ant Atta cephalotes with an entomopathogen to compare hygienic behavior and survival rates in the presence and absence of a previously activated immune encapsulation response. Entomopathogenic-challenged ants: (a) increased the production of infrabuccal pellets, formed by collecting detritus and fungal conidia and mixing them with antimicrobial compounds as a prophylactic behavior to avoid conidia germination; and (b) exhibited a reduced encapsulation response. Although the encapsulation response of insects is typically initiated within a few hours after infection, in our experiment neither pellet production nor encapsulation response depended on the timing of the prior immune challenge. Moreover, simultaneous activation of the immune system with both a foreign body (nylon implant) and entomopathogenic fungal conidia significantly reduced survival rates. Our findings suggest that when the ant immune system is chronically challenged to encapsulate a foreign body, its defensive capacity against a fungal pathogen is weakened.