Browsing by Author "Radchenko, Yury M."

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Active Thermoregulation in Lasius Fuliginosus Nests in Spring (Hymenoptera: Formicidae)
(Sapienza University of Rome, Rome, Italy, 2025) Stukalyuk, Stanislav; Radchenko, Yury M.; Balabukh, Vira
ENG: The aim of the study was to investigate characteristics of temperature conditions in Lasius fuliginosus nests in spring to possibly prove the spring warmup hypothesis. In spring (05.03 to 31.05.2024), 3 loggers, allowing measurements of temperature conditions were mounted on the outer walls of 3 L. fuliginosus nests in a deciduous forest near Kyiv (Ukraine). The temperature measurements were taken at 15-minute intervals. Simultaneously, the atmospheric air temperature was measured during the same period (at 3-hour intervals). Nests 1 and 2 were typical for this species: both in empty cores of oak trees (1 m diameter), while Nest 3 was auxiliary and located under a 0.05 m layer of oak bark. The physical data (air and nest wall temperatures) were used to construct a mathematical model of the thermal processes occurring in the core of a carton nest. The modelling showed that the anthills’ ability to maintain nest temperature in spring depends on their size and location inside the tree trunks exposed to environmental influence. The temperature inside a nest follows the average daily air temperature with a slight delay due to thermal inertia of the tree. The nest in tree #1 proved to be the most stable: even during cold spells as low as -5°C, the temperature in the core remained +25°C thanks to metabolic heat. Nest #2 also maintains the required temperature (+25°C) during temperature falls to +5°C. However, nest #3 does not provide conditions for offspring development during sudden cold snaps: the heat emitted is insufficient to compensate for losses at air temperatures below +20°C. This nest is not designed for active thermoregulation. It has been shown that L. fuliginosus are able to actively warm up their nest in spring, and the warmup rates (up to 25–26°C) are similar to the temperature conditions in the red forest ants’ anthills (Formica rufa group).
Characteristics of Thermal Processes in Ant Nests Built Under Stones (Hymenoptera: Formicidae)
(“Charles Darwin” Sapienza University of Rome, Italy, 2022) Stukalyuk, Stanislav; Radchenko, Yury M.
ENG: Ants prefer to nest under stones. This is due to temperature regimes favorable to the development of ant broods. In this paper, we investigated the influence of stone and ambient parameters on ant nests and created a model of thermal processes in ant nests under stones. The simulation results were compared with temperature measurements. Temperature was measured under 20 stones under different illumination conditions (sun, penumbra and shade) for 3 ant species (Myrmica rubra, Formica cinerea, Lasius niger) in Ukraine from April to August 2021. Stones were categorized as hot, warm and cold. Each stone was checked once a week for the number of workers and brood. Under two stones, tem¬perature was measured using loggers. The number of workers under hot stones in spring increased three weeks earlier than under cold and warm ones. In May-June, the maximum number of workers was recorded under hot stones. In July, the number of ants was minimal under all categories of stones. Larvae appeared under hot stones two weeks earlier than under other categories of stones. In August, the number of pupae under cold and warm stones was greater than under hot ones. Number of larvae and pupae was positively influenced by the diameter of the stone, whereas stone height did not exert an important role. Ants preferred to inhabit nests under large flat stones, which are easily heated in spring and warm the soil under them. Another important characteristic was the location of the stones. The highest brood development was noted in nests under stones in open areas well lit by the sun in the daytime. In summer ants migrated from under hot stones, because soil under it dry and warmed. Stones and their position may be important factors in accelerating the development of brood in colonies of ant species that do not have active thermoregulation.
Mixed Colonies of Lasius Umbratus and Lasius Fuliginosus (Hymenoptera, Formicidae): When Superparasitism May Potentially Develop into Coexistence: a Case Study in Ukraine and Moldova
(Organisation for Conservation and Study of Biodiversity (CSBD) in collaboration with ANeT-India, 2021) Stukalyuk, Stanislav; Radchenko, Yury M.; Gonchar, Oleksiy; Akhmedov, Ascar; Stelia, Valery; Reshetov, Alexander; Shymanskyi, Artem
ENG: In 2015, in the territory of Kyiv (Ukraine) and in 2012-2017 in Transnistria (Moldova), two mixed colonies consisting of two species of ants – Lasius fuliginosus and L. umbratus were observed. Another 2 mixed colonies were discovered in 2021 in the territory of the city of Rivne (Ukraine). The aim of the study was to describe the observed mixed colonies, analyze the interaction of workers of two species on the trails, and by mathematical modelling to determine the probability of preserving queens of both species as part of a mixed colony. On the trails of the colonies from Kyiv and Rivne, the number of workers of L. fuliginosus is slightly higher than that of L. umbratus, so is the number of L. Fuliginosus workers in the colony. Workers of both species were making contact both within the same species and interspecific contacts, but trophobiosis with aphids has been recorded only by L. fuliginosus. The most likely of the 4 options considered was the survival of the queens of both species, otherwise the dynamics of the population over 6 years of development (total population of the mixed colony from Kyiv: 27 thousand workers of L. umbratus, 72 thousand workers - L. fuliginosus and two colonies with same population from Rivne) is difficult to explain. The possibility of such mixed colonies co-existing for at least a few years is debated.