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An intimate view of the unique architecture of Harpegnathos saltwater nest using aluminum nest casts
Given the incredible variety in ant nest architecture, this experiment sought to evaluate how the nest architecture of Harpegnathos saltator differs from other species’ nests. To achieve the ability to evaluate the structure of H. saltator nest, we created experimental colonies varying in size from 20, 40, 60, 80 workers of Harpegnathos saltator in five-gallon buckets of sand and then allowing the colonies to grow for four months and twelve days. To create the nest casts, we developed a charcoal kiln out of a galvanized trash can and used a ceramic crucible to hold the aluminum being melted. Using molten aluminum to create nest casts of each colony produced, we obtained three poorly developed nests and one decent nest. The decent nest cast, the 80 worker H. saltator nest, was lacking key features of H. saltator nests that have been excavated in the field. However, they do share many of the same structures such as the shaping of the chambers. The ability of the experimental colonies to excavate the soil provided in the buckets to them was likely halted by poor penetration of water into superficial layers of the soil, thus making the soil too difficult to excavate and form the structures that are key elements of the species nest architecture. Despite these key challenges which the colonies faced, the 80-worker colony showed extensive vertical development and did display features associated with natural H. saltator colonies. Thus, given the display of some key features associated with characteristics of the H. saltator nests excavated in the field, it can be said that with some modification to technique that this is a viable avenue for future study of nest architecture and colony structure.
Insects are able to navigate their environments because they can detect hydrocarbons and volatile odors, but it is not clear which one has the fastest reaction when detected, or how much of a response can be produced due to either one. In order to determine which category of odorant is detected first as well as which one causes the highest response rate, data on electrophysiological responses from ants was analyzed. While the statistical tests can be done to understand and answer the questions raised by the study, there are various hydrocarbons and volatile odors that were not used in the data. Conclusive evidence only applies to the odorants used in the experiments.
Although social hierarchies are commonly found all throughout nature, the underlying mechanisms of their formation are still ambiguous. Hierarchies form through a wide range of interactions between subordinate and dominant individuals, and the ponerine ant Harpegnathos saltator provides the perfect model to explore such dominance behaviors. When the queen is absent or her fecundity levels drop below a certain threshold, H. saltator workers undergo a dominance tournament, in which several individuals emerge as gamergates, reproductive workers that are not queens. During this tournament, several characterizable dominance behaviors are exhibited (antennal dueling, dominance biting, and policing), which can be used to study the behavioral and social dynamics in the formation of a reproductive hierarchy. Colonies of 15, 30, 60, and 120 workers were created in duplicate, and their dominance tournaments were recorded to study how these interactions impact gamergate establishment. Rather than studying these behaviors as isolated incidents, responses to policing behaviors (timid, neutral, or aggressive) and their duration were recorded along with the frequency of dueling. Three groups were determined: dueling future gamergates (DFG), dueling future non-gamergates (DFNG) and non-dueling individuals (ND). DFNG received many more policing attacks and the duration of these interactions lasted much longer. DFG consistently exhibited the most dueling. Timid and neutral responses were more common than aggressive responses, perhaps due to energy conversation purposes. Peaks in dueling correspond to peaks in policing, highlighting the dynamic behavioral interactions necessary for the formation of a reproductive hierarchy.
Cities in the Global South face rapid urbanization challenges and often suffer an acute lack of infrastructure and governance capacities. Smart Cities Mission, in India, launched in 2015, aims to offer a novel approach for urban renewal of 100 cities following an area‐based development approach, where the use of ICT and digital technologies is particularly emphasized. This article presents a critical review of the design and implementation framework of this new urban renewal program across selected case‐study cities. The article examines the claims of the so‐called “smart cities” against actual urban transformation on‐ground and evaluates how “inclusive” and “sustainable” these developments are. We quantify the scale and coverage of the smart city urban renewal projects in the cities to highlight who the program includes and excludes. The article also presents a statistical analysis of the sectoral focus and budgetary allocations of the projects under the Smart Cities Mission to find an inherent bias in these smart city initiatives in terms of which types of development they promote and the ones it ignores. The findings indicate that a predominant emphasis on digital urban renewal of selected precincts and enclaves, branded as “smart cities,” leads to deepening social polarization and gentrification. The article offers crucial urban planning lessons for designing ICT‐driven urban renewal projects, while addressing critical questions around inclusion and sustainability in smart city ventures.`