Antlion larvae are fluid-feeding ambush predators that feed on arthropods trapped in their funnel-shaped pits built in sandy habitats; however, details are lacking about their feeding mechanism. Here we tested the hypothesis that the antlion, Myrmeleon crudelis, has adaptations that facilitate fluid feeding in sandy habitats. We measured contact angles of water droplets and used the capillary-rise technique to assess mouthpart wettability. A structural organization was discovered that provides a hydrophobic-hydrophilic wetting dichotomy that would simultaneously support self-cleaning and fluid uptake and is enabled by antiparallel movements of the maxillae. The mouthparts also are augmented by their material properties, including maxillae and mandible tips that are heavily sclerotized for piercing prey and mandibular teeth with resilin that would assist in preventing tooth breakage. Our findings provide insight on how antlion larvae have overcome the challenges of fluid feeding in sandy habitats, which likely contributed to their success and widespread distribution.

We administered droplets of dH2O onto the mandibles using a spray bottle and used contact angles of the droplets to assess wettability. The mandibles were divided into three zones to investigate the wettability along its length: Zone 1 (base of the mandible to tooth 1), Zone 2 (tooth 1 to tooth 3), and Zone 3 (tooth 3 to distal tip). The contact angles of three droplets were measured per zone on the dorsal and ventral sides to determine average droplet contact angles per zone for each individual. A second droplet experiment was performed on the same mandibles after they were washed in hexane (two washes, 15 min each) to remove cuticular waxes, and the same methodology was used to assess wettability.