Mating behavior of Petrobiellus akkesiensis captured from movies, viewed from the top. Counters indicate the time from the commencement of the experiment, i.e., when a male and a female were placed in the experimental arena. A–C Sequential frames of mating in Case I from Table 1 (captured from File S1). A At 8 sec after the commencement of the experiment (ACE), the male positions himself to the right of the female, placing his maxillary palps on her thorax. B At 2 min 9 sec ACE, the male grasps the basal part of the ovipositor with his penis. C At 12 min 45 sec ACE, even after the penis releases the ovipositor, the male continues to hold and vibrate the female for a short while. D A single frame from Case V in Table 1 (captured from File S2), at 46 sec ACE. Soon after ovipositor-holding is established, the male’s ventral sacs begin to swell; a pair of ventral sacs in each of the abdominal segments VII and VI can be observed. — Abbreviations: MxP – maxillary palp; VS6, 7 – ventral sacs VI and VII. — Scale bars: 5 mm.