“…Ancistrocerus Wesmael, 1836, is one of the largest genera of the eumenine wasps. With 116 described species, this genus is native to most zoogeographical regions except the Australian (Piekarski et al, 2017). Females of these wasps usually nest in preexisting cavities while some Palaearctic and Nearctic representatives of the genus, such as A. albophaleratus (de Saussure, 1855), A. catskill (de Saussure, 1852), A. densepilosellus Cameron, 1911, A. japonicus (von Schulthess, 1908), A. lutonidus Bohart, 1974, A. oviventris (Wesmael, 1836), and A. waldenii (Viereck, 1906), are known to construct aerial mud nests attached to stones (Iwata, 1938; Buck et al, 2008; Olszewski and Fateryga, 2023).…”