Morphological adaptations shape interactions between a kleptoparasitic cricket and its social insect hosts

Myrmecophiles are organisms that associate with ants, ranging from casual visitors to fully integrated in the colony. They further vary in host specificity, from generalists that utilize multiple hosts to specialists adapted to a single host species. Ant colonies defend themselves against invaders using a nestmate recognition system of cuticular hydrocarbon profiles. To circumvent these defenses, myrmecophiles may use chemical deception and deploy a range of morphological and behavioral strategies that work together in tandem to fool the host or circumvent its aggression. These strategies may scale in complexity with the degree of specialization. Ant crickets in the genus Myrmecophilus are obligate kleptoparasites that exploit ant colonies by stealing resources, acquiring host chemical profiles through grooming, and intercepting food exchanges. Myrmecophilus pergandei, a host-generalist species native to the U.S., uses a range of hosts. This study used scanning electron microscopy (SEM) and behavioral bioassays to examine morphological traits and behaviors that facilitate host integration. We compared M. pergandei to host-specialist ant cricket species through SEM, analyzing adaptations that support their different lifestyles. We further examined possible changes in interactions between M. pergandei and its ant hosts by isolating crickets to degrade their chemical profiles and modifying body parts identified via SEM that may influence their interactions with their host. Results showed increased host aggression when crickets were isolated or when they had impaired appendages, with or without isolation. Ant cricket success appears closely tied to sensory structures including antennae, cerci, and sensory hairs, which help them respond to host cues.