Novel nesting of ants in bee cocoons in empty shells of terrestrial gastropods

Several species of ants were reported to place their nests inside empty shells of larger terrestrial gastropods. The structure of their nests was never studied in detail. We recorded 14 species of ants nesting in empty shells of terrestrial gastropods in various habitats of the Czech Republic, of which especially small species of the genus Temnothorax were the most numerous. In steppic habitats, nests of Temnothorax unifasciatus were placed inside the cocoons of the shell-nesting solitary bee Osmia bicolor in several cases. This bee is a specialist for nesting inside empty shells and is locally common and numerous in steppic habitats in Central Europe. In two nests, remnants of a dead bee were found inside the cocoon, together with the colony of T. unifasciatus. The adult of O. bicolor probably died inside the nest and was partly eaten by the ants suggesting a scavenging behaviour. This finding is unique and interesting, brings new insight to the biology of ants and a challenge for further studies on ants nesting in empty shells of gastropods.已有研究报道，多种蚁类会将巢穴构筑于大型陆生腹足类（terrestrial gastropods）的空壳内，但此类巢穴的结构尚未得到细致探究。本研究在捷克共和国的多种生境中，记录到14种依托陆生腹足类空壳筑巢的蚁类，其中扁胸切叶蚁属（Temnothorax）的小型蚁类占比最高。在草原生境中，有多例单带扁胸切叶蚁（Temnothorax unifasciatus）的巢穴被发现于独居蜂双色壁蜂（Osmia bicolor）的茧内；该蜂为专性依托空壳筑巢的物种，在中欧的草原生境中本地分布广泛且种群数量可观。在两处巢穴中，研究人员于茧内同时发现了单带扁胸切叶蚁的种群与一只死亡双色壁蜂的残骸。推测该双色壁蜂成虫死于巢内，并被蚂蚁部分取食，这表明蚂蚁存在食腐行为。该发现兼具独特性与研究价值，为蚁类生物学研究提供了全新视角，同时也为后续针对腹足类空壳筑巢蚁类的相关研究提出了新的课题。