Probable marking behavior of Cerceris clypeata (Philanthinae, Crabronidae, Hymenoptera)

Males of Cerceris clypeata appear to mark grass stems and other plant parts with secretions from cephalic glands by placing the head and tip of the abdomen on the plant as they walk up the stem or around the leaf of the marked plant. Behavior of this sort has rarely been recorded for Cerceris but is common in the Philanthinae including some members of the Cercerini, which includes Cerceris. Males of C. clypeata very occasionally defended their small marking site against intruders but no nests or females were observed during the study. The abdomen dragging behavior of C. clypeata and another member of the genus suggest that marking behavior is ancestral for the subfamily.