Ptilocnemus lemur: the ant assassin

To the uninitiated, this may look like a harmless (albeit strange) hemipteran, but it is in fact a feather-legged assassin bug – a killer, that is trained in the subversive arts of ant sedation. Although the majority of assassin bugs (Reduviidae) are generalist predators, some are known to prey upon certain groups of arthropods (e.g. termites). Ptilocnemus lemur (and some other members of the Holoptilinae), however, has taken up the challenging task of preying upon ants. It manages this by utilising a specialised structure known as a “trichome” (hair-like structure that discharges secretions) that is located on the ventral abdomen. The trichome and associated glandular areas are thought to produce secretions which attract and paralyse ants, allowing the bug to pierce and kill the ants with its rostrum. Once its digestive saliva is done dissolving the tissues of its prey, it can then suck up the ants bodily fluids at its leisure.

These assassins usually position themselves near a trail of ants to which they signal to with their conspicuous rear legs. They do this in a jerky motion that, along with the legs being large and hairy, is quite obvious to the ants. This signalling is then reinforced with a pheromone produced from the trichome (and associated glands) that further entices the ants to come near. Eventually the bug will lift itself up and reveal the trichome to the ants, who then may taste the secretion directly from its source. An ant may become sedated by the effects of these chemical secretions. The assassin bug can then safely strike at its prey, killing it and eventually feed on its bodily juices.

I was quite lucky to observe the act of predation, above, one night. The Camponotus ant was initially observed dragging along the assassin bug as if it was it’s prey – whether it was attracted to the secretions of the trichome or if it had just found it via random foraging, I am uncertain. The assassin bug was happy to go along with this, until eventually it struck at the thin joint between the ants head and pronotum with its rostrum. It then shook the ant violently from side to side (possibly to prevent the ant from biting it) before retreating to a crack in the bark. It did not take long for the ant to die. The assassin bug was later observed to feed on the ant via the antennal socket. For further observations and to see the photos at larger sizes, click through the photos to visit my Flickr, and be sure to watch this clip of them in action from Life in the Undergrowth.