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Laboratory studies on insects face the dual challenge of maintaining organisms under artificial conditions, and in reduced spaces while mimicking the species’ ecological requirements as much as possible. Over decades, myrmecologists have developed and continuously improved laboratory methods and artificial nests for rearing ants. However, the setups commonly used to house colony fragments of few individuals or even isolated individuals present disadvantages such as insufficient ventilation, difficult access to specific workers, and problems with water delivery. Here, we developed and tested a new setup for keeping ants or similar sized insects in small groups. The setup consisted of a Petri dish containing a piece of plaster connected underneath to a water tank by a sponge. The sponge is immersed in the water on one side and embedded in the plaster on the other side, maintaining the plaster permanently moist and thus offering a water source to the ants. We tested the setup with two ant species of different sizes, Platythyrea punctata and Cardiocondyla obscurior in feeding, starvation, and desiccation conditions. Our results showed that our new setup worked equally well for both species in all conditions in comparison to a more conventional setup with the advantage of reducing maintenance costs and ant manipulation, but also preventing death by drowning and offering water ad libitum . The setup was quick to build, with cheap and reusable materials for further experiments. Therefore, we are confident that it will facilitate future studies on isolated or small groups of individuals and that such a standardized setup will make future studies more comparable.

Background Elderly people in nursing homes are particularly vulnerable to COVID-19 due to their age, the presence of comorbidities, and community living. On March 14, 2020, at the beginning of the first epidemic wave of COVID-19 in France, a cluster was reported in a nursing home in the Nouvelle-Aquitaine region. We monitored the outbreak as well as the infection prevention and control (IPC) measures implemented. Methods A confirmed case was defined as laboratory-confirmed COVID-19 in a resident or staff member present in the nursing home between March 7 and May 1, 2020; and a probable case as a person presenting an acute respiratory illness after contact with a confirmed case. Symptomatic inpatient residents and symptomatic staff members were systematically tested for SARS-CoV-2. In addition, two screening sessions were held on site. Results We identified 109 cases (98 confirmed, 11 probable). The attack rate was 66% among residents and 45% among staff. Half of all cases were identified during the screening sessions. One-quarter of cases had minor symptoms or were asymptomatic. The case fatality rate among residents was 29%. IPC measures were rapidly implemented such as the quarantine of residents, the reinforcement of staff personal protective equipment, and home quarantine of staff testing positive, which were supplemented in April by systematic controls at the entrance of the nursing home and the creation of additional staff break rooms. Conclusions This outbreak confirmed the considerable health impact of SARS-CoV-2 transmission in a nursing home. In addition to the implementation of IPC measures, the early detection of cases through the screening of residents and staff is essential to identify asymptomatic and pre-symptomatic cases and limit the spread of the virus.

An important question in evolutionary biology is to identify the mechanisms that control the number of reproductives in social groups. Ants are appropriate models to address this question because of the variety of their social structures both within and between species, making this taxon suitable for initiating comparative studies to examine the drivers of this diversity. In this study, we developed a comparative approach between populations of the ponerine ant Odontomachus hastatus from Brazil and French Guiana. In Brazil, monogynous and polygynous colonies coexist in the same populations, whereas only monogynous colonies are present in French Guiana. We combined ecological, behavioural and chemical analyses to identify the factors associated with the expression of this social polymorphism. In Brazil, nest densities were higher than in French Guiana, but nesting sites were available in large quantities in both areas, indicating that habitat saturation is probably not the cause of social polymorphism. We did not detect any difference in queen size, regardless of the social structure of the colonies, suggesting that dispersal strategies may be similar between monogynous and polygynous populations. We found no influence of social structure on aggression intensity in dyadic encounters between workers. Last, we showed that the level of aggression increased with both geographical and chemical distance, but we did not find any difference in cuticular profiles between monogynous and polygynous colonies. Overall, the determinism of social polymorphism in O. hastatus still eludes us and calls for further field experiments coupled with genetic approaches.

While reproduction and longevity are negatively correlated in a large number of animals, this fundamental trade-off appears to be absent from social insect queens. Here, we examine the distribution of the life-spans of queens and their mates and the age-trajectory of reproduction in experimental colonies of the Pacific tramp ant Cardiocondyla cf. kagutsuchi. Queens of Cardiocondyla are generally short-lived (0.5-2 years), which allows determining their lifetime reproductive success and establishing mortality tables. We show that the queen's total number of sexual offspring is positively associated with its life-span. Regular counts of eggs, larvae, and pupae suggest that more fecund queens live longer than less fecund queens and that an early onset of sexual production does not negatively affect the queen's life-span. This corroborates the view that the costs of reproduction are not born by the queen itself. The number of eggs present in colonies increased with queen's age until shortly before death, indicating negligible reproductive senescence. Sex ratios were strongly affected by the origin of queens but neither by colony size nor total productivity. Several queens produced only males late in their lives, suggesting the occurrence of sperm depletion. Male life-span was not correlated with any other studied trait. Our study shows that the ant genus Cardiocondyla provides a suitable model system to investigate the evolution of life-span in social insect queens and males.

Of particular importance in shaping species assemblages is the spatial heterogeneity of the environment. The aim of our study was to investigate the influence of spatial heterogeneity and environmental complexity on the distribution of ant functional groups and species diversity along altitudinal gradients in a temperate ecosystem (Pyrenees Mountains). During three summers, we sampled 20 sites distributed across two Pyrenean valleys ranging in altitude from 1,009 to 2,339 m by using pitfall traps and hand collection. The environment around each sampling points was characterized by using both physical and land-cover variables. We then used a self-organizing map algorithm (SOM, neural network) to detect and characterize the relationship between the spatial distribution of ant functional groups, species diversity, and the variables measured. The use of SOM allowed us to reduce the apparent complexity of the environment to five clusters that highlighted two main gradients: an altitudinal gradient and a gradient of environmental closure. The composition of ant functional groups and species diversity changed along both of these gradients and was differently affected by environmental variables. The SOM also allowed us to validate the contours of most ant functional groups by highlighting the response of these groups to the environmental and land-cover variables.

Two cases are reported of an apparently distinct type of immune disorder. Beginning with mild anaemia and widespread massive lymphadenopathy, the disease progressed to a fatal autoimmune type haemolytic anaemia. Serum investigation showed polyclonal hypergamma-globulinaemia and some autoantibodies. Repeat lymph node biopsies in each case showed hyperplasia within B lymphocyte territory (follicular hyperplasia and polyclonal plasmacytosis with IgG predominance) and atrophy of T dependent areas. Dilatation of lymph sinuses, vascular proliferation, and sclerosis were striking features. This appears to be a new entity, and reasons are given for separating this disease from other pseudotumourous lymph node disorders associated with dysimmunity.

An ultrastructural cytochemical study of lysosomal acid phosphatase was performed on leukemic cells in a case of chronic lymphocytic leukaemia of T cell origin (T-CLL). The cells showed inclusion bodies known as parallel tubular arrays, which often lay within acid phosphatase-positive, membrane-bound spaces. This suggests their lysosomal location.

Social insects, such as ants and bees, are known for their highly efficient and structured colonies. Division of labour, in which each member of the colony has a specific role, is considered to be one major driver of their ecological success. However, empirical evidence has accumulated showing that many workers, sometimes more than half, remain idle in insect societies. Several hypotheses have been put forward to explain these patterns, but none provides a consensual explanation. Task specialisation exploits inter-individual variations, which are mainly influenced by genetic factors beyond the control of the colony. As a result, individuals may also differ in the efficiency with which they perform tasks. In this context, we aimed to test the hypothesis that colonies generate a large number of individuals in order to recruit only the most efficient to perform tasks, at the cost of producing and maintaining a fraction of workers that remain inactive. We developed a model to explore the conditions under which variations in the scaling of workers’ production and maintenance costs, along with activity costs, allow colonies to sustain a fraction of inactive workers. We sampled individual performances according to different random distributions in order to simulate the variability associated with worker efficiency. Our results show that the inactivity of part of the workforce can be beneficial for a wide range of parameters if it allows colonies to select the most efficient workers. In decentralised systems such as insect societies, we suggest that inactivity is a by-product of the random processes associated with the generation of individuals whose performance levels cannot be controlled.

Division of labour occurs in a broad range of organisms. Yet, how division of labour can emerge in the absence of pre-existing interindividual differences is poorly understood. Using a simple but realistic model, we show that in a group of initially identical individuals, division of labour emerges spontaneously if returning foragers share part of their resources with other group members. In the absence of resource sharing, individuals follow an activity schedule of alternating between foraging and other tasks. If non-foraging individuals are fed by other individuals, their alternating activity schedule becomes interrupted, leading to task specialisation and the emergence of division of labour. Furthermore, nutritional differences between individuals reinforce division of labour. Such differences can be caused by increased metabolic rates during foraging or by dominance interactions during resource sharing. Our model proposes a plausible mechanism for the self-organised emergence of division of labour in animal groups of initially identical individuals. This mechanism could also play a role for the emergence of division of labour during the major evolutionary transitions to eusociality and multicellularity. Division of labour, where members of a group specialise on different tasks, is a central feature of many social organisms. Using a theoretical model, the authors demonstrate that division of labour can emerge spontaneously within a group of entirely identical individuals.