Pinching of right foreleg (A), midleg (B), and hindleg (C) and pinching of tarsus of right hindleg (beetle in rear-end view), with leg in raised position (D) and in downward position (E). [Bar (C) = 0.5 cm.]

Pinching of base of left midleg (A), of distal portion of femur of right midleg (B), and of base of femur of right hindleg (C) and pinching of distal portion of left femur, with femur positioned beside body (D) and positioned behind abdominal tip (E). (A–C) Ventral view of abdomen. (D) Dorsal view of abdominal tip. (E) End-on view of abdominal tip.

(A) Pinching of prothorax from above. A faint trace of the discharge is seen in white, emerging forward from the abdominal tip. (B) Poking of left flank of abdomen. Note that the abdominal tip (dorsal view) is rotated to the left and that the spray is bouncing off the left reflector. (C) Poking of abdominal tip just to the left of glandular opening. The secretion is bouncing off the left reflector and has almost drenched the tip of the forceps. (D) Poking of the abdominal tip, just to the right of the midline, above the gland opening. The secretion is bouncing off the right reflector and is hitting the tip of the forceps. (E) Undisturbed abdominal tip, showing the two sclerotized reflectors (light brown) in their unexposed position. (F) Comparable to preceding (scanning electronmicrograph). The arrows denote the curved slit-like opening through which the spray is expelled. The two reflectors (rf), shown in their unexposed position, form the lower “lip” of this opening. The upper lip (lp) is a membranous fold. [Bar (E) = 0.5 mm.]

Schematic representation of an encounter between an ant and a bombardier beetle (reprinted from ref. 24 by permission).