Spatial pattern

Spatial patterning is an important mechanism of organization in social insect colonies, both within and across nests (if polydomous); this creates informational heterogeneity.

Worker sorting

In the first demonstration of an organizational mechanism for creating polymorphic workers in social insect colonies, we demonstrated that nurse bees stick to the center of the nest but brood is spread across the nest, leading to less-fed, smaller pupae in the periphery.

Nonetheless, bumble bees maintain development temperature in all brood across the nest.

Workers of some other tasks are also non-randomly sorted across the nest area.

Jandt JM, Dornhaus A 2009 Spatial organization and division of labor in the bumble bee, Bombus impatiens Animal Behaviour 77: 641-651 - pdf - bumble bees, like some ants, maintain spatial fidelity zones in the nest (small areas where they are predictably found), with brood care workers/smaller workers in smaller zones nearer the nest center, and foragers near the periphery even when inactive; this paper is also the first to demonstrate body size-based division of labor in bumble bees for tasks other than foraging, and shows a weak age differences between tasks

Couvillon MJ, Dornhaus A 2009 Location, location, location: larvae position inside the nest is correlated with adult body size in worker bumble bees (Bombus impatiens), Proceedings of the Royal Society: Biological Sciences 276: 2411-2418 - pdf - larvae nearer the center of the nest are fed more and turn into larger pupae; together with the results above that nurses stick to the center, this provides a mechanism for generating body size variation in concurrently raised brood

Jandt JM, Dornhaus A 2011 Competition and cooperation: bumblebee spatial organization and division of labor may affect worker reproduction late in life, Behavioral Ecology and Sociobiology 65: 2341-2349 - pdf - workers who reproduced after the queen was gone were larger, older, and had been both more inactive and staying away from the queen when she was still around; suggesting inactive workers may gain selfish benefits later even if not immediately

Kelemen E, Dornhaus A 2018 ‘Lower temperatures decrease worker size variation but do not affect fine-grained thermoregulation in bumble bees’, Behavioral Ecology and Sociobiology 72: 170 - pdf - bees maintain high temperatures for brood in all locations, but not honeypots; under higher ambient temperatures, more size variation in brood is produced

Architecture

Since spatial distribution of workers in the nest matters, it is likely that nest cavity shape and built architecture have important roles to play; this new area of research is being explored.

We show that even simple built walls by Temnothorax colonies have repeatable, and thus possibly relevant, traits.

First description of social pseudoscorpion nests in detail.

DiRienzo N, Dornhaus A 2017 ‘Temnothorax rugatulus ant colonies consistently vary in nest structure across time and context’, PLoS One 12: e0177598 - pdf - colonies build walls to encircle the used part of their nest cavity; these are thicker when colonies have more brood, thicker, longer, and heavier with higher ambient humidity, and colonies differ (repeatably) in the traits of walls they build

Chapin KJ, Kittle A, Dornhaus A 2022 Social pseudoscorpion nest architecture provides direct benefits to group members and rivals the efficiency of honey bees, Journal of Arachnology 50: 323-334 - pdf - detailed quantitative descriptions of nests of social pseudoscorpions, which consist of multiple molting chambers or ‘cells’; calculation of the amount of silk saved by cooperation

Chism GT, Nichols W, Dornhaus A 2024 Cavity geometry shapes overall ant colony organization through spatial limits, but workers maintain fidelity zones, Animal Behaviour 216: 195-211 - pdf - bioRXiv - distribution of colony members differs between tube- and circle-shaped nests and shows non-random distribution, but spatial fidelity zones remain the same

not yet peer reviewed: Chism GT, Dornhaus A 2022 Temnothorax rugatulus ants do not change their nest walls in response to environmental humidity, bioRXiv - external humidity does not have an effect on built nest walls, but ant colonies have preferences for particle sizes and wall density that are consistent between field and lab

Networks

Networks among spatially viscous or unmoving agents show high clustering, and slow information flow along the global network.

More work in this area, particularly with large empirical datasets, is needed.

Blonder B, Dornhaus A 2011 'Time-ordered networks reveal limitations to information flow in ant colonies', PLoS One 6: e20298 - pdf - using a large empirical dataset of ant-ant interactions, we show that indeed spatial viscosity in movement strongly limits information flow in ant colonies

Charbonneau D, Blonder B, Dornhaus A 2013 ‘Social insects: a model system for network dynamics’, in: Holme P and Jari S: Temporal Networks. Springer books - pdf - conceptual review paper showing examples of network analysis in social insect research and calling for more use of such techniques

Polydomy

Multiple nests can be used by ants to effectively exploit a larger area; and ‘outstations’ may be nest-like even without brood in them.

Also, ants make cockroach jerky.

Search

Collective search pattern does not seem to involve much coordination between ants (at least in Temnothorax). However, individuals have complex search strategies: systematic meandering combined with random walks, strong consistent differences between individuals, changes as ants become familiar with their environment, and effects of very subtle environmental heterogeneities.

Lanan MC, Dornhaus A, Bronstein J 2011 'The function of polydomy: the ant Crematogaster torosa preferentially forms new nests near food sources and fortifies outstations', Behavioral Ecology and Sociobiology 65: 959-968 - pdf - ants make beef jerky (out of cockroaches); colonies may inhabit multiple nest sites, and if so, often found new nests near valuable locations; and while a ‘nest’ technically is only a cavity with brood in it, ants also inhabit ‘outstations’ (without brood, but with adults and which are fortified, so not just short-term shelters for foragers); workers are preferentially associated with a particular nest even if there is traffic between nests

Popp S, Dornhaus A 2023 ‘Ants combine systematic meandering and correlated random walks when searching for unknown resources’, iScience 26: 105916 - pdf - as ants move in large empty arena, their turn directions autocorrelate, such that they meander regularly, changing turn direction roughly every 10 mm (3 body lengths). This reduces self-crosses and dispersion from the nest, and constitutes a form of systematic search (with stochastic elements). Such a combination of random walking with systematic search may be a compromise between efficiency and robustness of search.

Popp S, Dornhaus A 2023 ‘Ant colonies explore novel environments with more slower, curvier walks, particularly near the nest’, Insectes sociaux 70: 463–474 - pdf - colony-level exploration activity decreased with time, but only within a roughly 1 m radius around the nest, possibly reflecting a shift from familiarization (or marking) to searching. Individuals’ movements overall also became slightly straighter and faster across and within days.

Popp S, Dornhaus A 2024 ‘Collective search in ants: Movement determines footprints, and footprints influence movement’, PLoS One 19: e0299432 - pdf - we show that geometric constraints and side-effects can generate artefacts in analyzing search paths, particularly when it comes to area preferences. Nonetheless, even controlling for these artefacts we find that ants prefer to walk on areas with more footprint pheromone (inferred from data on previous ant walks on the same surface). However, search density around an ant colony is more affected by individual differences in movement pattern and local spatial heterogeneities.