How Not to Be Turned into a Zombie

Abstract

The emerald jewel wasp (Ampulex compressa) is renowned for its ability to zombify the American cockroach (Periplaneta americana) with a sting to the brain. When the venom takes effect, the cockroach becomes passive and can be led by its antenna into a hole, where the wasp deposits an egg and then seals the exit with debris. The cockroach has the ability to walk, run, or fly if properly stimulated, but it does not try to escape as it is slowly eaten alive by the developing wasp larva. Although the composition and effects of the wasp’s venom have been investigated, no studies have detailed how cockroaches might prevent this grim fate. Here it is shown that many cockroaches deter wasps with a vigorous defense. Successful cockroaches elevated their bodies, bringing their neck out of reach, and kicked at the wasp with their spiny hind legs, often striking the wasp’s head multiple times. Failing this, the elevated, “on-guard” position allowed cockroaches to detect and evade the wasp’s lunging attack. If grasped, the cockroaches parried the stinger with their legs, used a “stiff-arm” defense to hold back the stinger, and could stab at, and dislodge, the wasp with tibial spines. Lastly, cockroaches bit at the abdomen of wasps delivering the brain sting. An aggressive defense from the outset was most successful. Thus, for a cockroach not to become a zombie, the best strategy is: be vigilant, protect your throat, and strike repeatedly at the head of the attacker.

Predators as drivers of insect defenses

“…Kicking and striking are considered simple defensive behaviors, because these actions do not require the development of specific organs. Cockroaches have been observed to kick parasitoid wasps to defend themselves (Catania 2018), whereas some hawkmoth larvae use their heads to strike antagonists (Walters et al 2001;Sugiura & Takanashi 2018).…”

Getting the Most Out of Your Zombie: Abdominal Sensors and Neural Manipulations Help Jewel Wasps Find the Roach’s Weak Spot

“…For these data adult female cockroaches were used as hosts. Adult cockroaches often successfully defend themselves by kicking with their hind legs, thereby deterring the wasp's attack [Fox et al, 2009;Catania, 2018]. Therefore, for this first part of the study, the hind legs were removed to facilitate host handling.…”

“…The struggle between these 2 contestants begins when a stalking jewel wasp discovers and approaches a cockroach. If the roach is vigilant it may put up a successful defense [Williams, 1942;Fox et al, 2009;Catania, 2018] by standing tall (stilt-standing), thus increasing the distance between its body and the wasp. This posture allows the roach to use its mechanosensitive and barbed legs as a roadblock of sorts.…”

“…At the same time, stilt-standing allows the roach to kick at the wasp with its powerful, spiny hind legs. Most wasps are deterred after receiving multiple kicks to the head [Catania, 2018].…”

Comparative morphology of the musculature of the sting apparatus in Ampulex compressa (Hymenoptera, Ampulicidae) and Sceliphron destillatorium (Hymenoptera, Sphecidae)

“…After provisioning, the cells are sealed with mud and either additional cells or a new nest is constructed (Bohart andMenke 1976, Fateryga andKovblyuk 2014). A. compressa preys upon cockroaches and its unusual stinging behaviour is well documented (Haspel et al 2003, Libersat 2003, Catania 2018: The adult female grasps the lateral margin of the cockroach's pronotum, then bends her metasoma downwards to sting the cockroach for paralyzing. Two stings accurately hit the ganglions in the head and thorax.…”