part_of helcium SIBO:0000108 Helcium- The very reduced and specialized presclerites of abdominal segment 3, which form a complex articulation within the posterior foramen of the petiole. In general the helcium is mostly or entirely concealed within the posterior orifice of the petiole, but in certain groups it is partly visible. Disarticulation of abdominal segments 2 and 3 is necessary to examine the structure and its variation in detail. See also Abdomen. (Bolton, B. (1994). Identificstion guide to the ant genera of the world. Cambridge, Mass., Harvard University PRess. pp.1-222). sibo waist