To kill or be killed: predatory behaviour of an araneophagic assassin bug, Stenolemus bituberus (Heteroptera, Reduviidae)

Web-invading araneophagic predators hunt a dangerous prey, and thus risk becoming the hunted rather than the hunter. As a result, these predators require considerable skill when hunting. An Australian araneophagic assassin bug, Stenolemus bituberus (Heteroptera, Reduviidae), is known to hunt a wide range of spiders by invading their webs. We observed the predatory behaviour of S. bituberus hunting 5 species of sympatric spider: Achaearanea sp. (Theridiidae), Achaearanea extridium (Theridiidae), Badumna longinqua (Desidae), Pholcus phalangioides (Pholcidae) and Uloboridae sp., all of which constitute a part of the natural prey range of S. bituberus. Stenolemus bituberus utilises two distinct predatory strategies whilst hunting these spiders: (1) luring, wherein S. bituberus manipulates the silk of the spider webs, appearing to attract the resident spider within attacking range; and (2) stalking, in which S. bituberus stealthily approaches and attacks the resident spider. We propose that the luring strategy adopted by S. bituberus may be a form of vibratory aggressive mimicry, a hypothesis that we are currently testing using a combination of comparative and playback experimental techniques.