Raghavendra Gadagkar

Division of labour (DoL) is of prime importance in the success of social insects in various ecosystems and benefits their colonies by increasing efficiency and productivity. This review summarizes more than three decades of experimental evidence collected towards understanding the emergence and maintenance of division of labour in the Indian tropical paper wasp Ropalidia marginata . This primitively eusocial species provides an interesting variation between newly founded colonies and mature colonies in terms of the behavioural mechanisms regulating division of labour. Newly founded colonies rely on physical dominance behaviour for establishing division of labour. Workers in mature post-emergence colonies continue to implement physical dominance as a way to regulate non-reproductive division of labour in a decentralized manner, while the queens switch to chemical regulation of worker reproduction. We discuss experiments that build evidence toward establishing R. marginata as an important model for understanding the origin and maintenance of division of labour. This article is part of the theme issue ‘Division of labour as key driver of social evolution’.

The yellow crazy ant, or the long-legged ant, Anoplolepis gracilipes (formerly Anoplolepis longipes) - named so for its meandering movements when disturbed, possibly owing to its long legs and antennae - is globallywidespread and currently classified as one of '100 of the world's worst invasive species' (Lowe et al. 2000). This status is assigned to species that are non-native in a region and cause significant negative ecological and/or socioeconomic impacts, including declines in native biodiversity, changes in native ecosystem structure and function, and the breakdown of native biogeographic realms. Possibly, themost devastating and multipronged impacts of A. gracilipes have been observed on island ecosystems, such as on Christmas Island in the Indian Ocean, where it impacted the entire island ecosystem by reducing arthropod, reptile, bird, and mammalian diversity on the forest floor and canopy, causing an 'invasional meltdown' (O'Dowd et al. 2003).

I enjoyed reading this article on Anthropogenic Biodiversity. This is certainly a neglected topic. The only thing I found missing in it was any reference to the extensive work of EK Janaki Ammal. Please note that she also published extensively in _Cu...

In social insect colonies, food transferred through space and time via nestmates carries both nutrition and information. We study the mechanism of spatio-temporal coordination (or the lack thereof) between multiple wasps for them to optimally solve the problem of feeding randomly placed larvae in a social insect colony. We followed each morsel of food brought into semi-natural colonies of the tropical paper wasp Ropalidia marginata, in each of 36 feeding bouts until the food was exhausted. We found that most acts of feeding larvae are performed by wasps that unload food from foragers, but unloading itself is highly skewed among individuals. We also found that larvae closer to the nest center were fed more frequently than those at the periphery, irrespective of their developmental stage. This differential feeding may have fitness consequences as it is known that well-fed larvae become voracious feeders as adults and have a higher likelihood to become reproductives. Using the analogies of the travelling salesman problem and the Hamiltonian path problem, we showed that individuals which disburse food to more larvae within a feeding bout adopted paths that were considerably shorter than expected by chance while the distinction between adopted and random routes was not as pronounced when the number of larvae fed in a bout was fewer. There was no spatial segregation between wasps feeding larvae in parallel, possibly building redundancy and avoiding larval starvation across bouts. Understanding the spatial organization of food transfer may be a key to understanding how insect societies achieve efficient social organization and division of labor. Significance: The limited studies on within-nest spatial organization of food distribution have been performed on ants and not primitively eusocial insects like wasps that contain randomly placed yet trackable larvae within the colony. We address the gap in a holistic understanding of spatial organization of food distribution through our study in the social wasp Ropalidia marginata . Through the lens of task partitioning, colony-level larval landscape, and spatial strategies adopted at individual and collective scales, our study presents one of the most detailed account of behavioral and spatio-temporal data mapping sources and sinks of food in a colony chronologically. We found that feeding routes adopted by wasps while feeding randomly placed larvae within a colony may not be a result of random walk but instead the degrees of route optimization based on the food load available to distribute within each feeding bout. We suggest paper wasp colonies to be ideal model systems for spatial studies owing to their observable colony sizes and randomly placed brood. Understanding the mechanism of colony-level problem solving by individuals with limited local information has widespread real-life applications besides a better understanding of social organization in colonies of social insects.