Circadian rhythms, which respond to the day-night cycle on the earth, arise from the endogenous timekeeping system within organisms, called the “biological clock.” For accurate circadian rhythms, daily fluctuations in light and temperature are considered one of the important time cues. In social insects, both abiotic and biotic factors (i.e., social interactions) play a significant role in activity-rest rhythm regulation. However, it is challenging to monitor individual activity-rest rhythms in a colony because of the large group size and small body size. Therefore, it is unclear whether individuals in a colony exhibit activity-rest rhythms and how social interactions regulate their activity-rest rhythms in the colony. This study developed an image-based tracking system using 2D barcodes for Diacamma cf. indicum from Japan (a monomorphic ant) and measured the locomotor activities of all colony members under laboratory colony conditions. We also investigated the effect of broods on activity-rest rhythms by removing all broods under colony conditions. Activity-rest rhythms appeared only in isolated ants, not under colony conditions. In addition, workers showed arrhythmic activities after brood removal. These results suggested that a mixture of social interactions, and not light and temperature, induces the loss of activity-rest rhythms. These results contribute to the knowledge of a diverse pattern of circadian activity rhythms in social insects.

昼夜节律对地球上的昼夜循环做出反应，产生于生物体内的内源性计时系统，称为“生物钟”。对于准确的昼夜节律，光和温度的每日波动被认为是重要的时间线索之一。在社会性昆虫中，非生物和生物因素（即社会相互作用）在活动-休息节律调节中发挥着重要作用。然而，由于群体规模大且体型较小，因此在群体中监测个体活动-休息节律具有挑战性。因此，目前尚不清楚群体中的个体是否表现出活动-休息节奏以及社会互动如何调节他们在群体中的活动-休息节奏。本研究开发了一种基于图像的跟踪系统，使用 2D 条形码用于Diacamma cf。来自日本的indicum（一种单态蚂蚁）并在实验室群体条件下测量了所有群体成员的运动活动。我们还通过在菌落条件下去除所有育雏来研究育雏对活动-休息节律的影响。活动-休息节律仅出现在孤立的蚂蚁中，而不出现在群体条件下。此外，工人在取卵后表现出心律不齐的活动。这些结果表明，社交互动的混合，而不是光和温度，会导致活动-休息节奏的丧失。这些结果有助于了解群居昆虫昼夜节律的多种模式。