Meeting Abstract
Drilling in solid substrates with slender probes is challenging, but is normal behavior of many parasitic wasps. Females use their thin ovipositors to search for and deposit their eggs in/next to hosts hidden within the substrates. The ovipositor consists of three valves that are longitudinally connected with a rail-like structure, enabling them to slide along each other. Alternating valve movements have been hypothesized to play a role in damage avoidance and steering during probing. We tested these hypotheses in vivo by quantifying the probing kinematics of the parasitoid Diachasmimorpha longicaudata (Braconidae) in transparent gels of two different stiffnesses. The quantification of valve motion revealed their different functional roles and effects on the shape of the ovipositor tip. We further investigated the valves’ mechanical properties by measuring their bending resistance. We show that wasps were able to probe in any direction relative to their body. Steering of the ovipositor is achieved by changing the shape of its tip, which is done by adjusting the valve offset. Upon the protraction of the ventral valves, the asymmetry was enhanced due to curving of these valves toward the dorsal one which increased the asymmetry of the tip forces. Furthermore, alternating valves were always used when drilling in stiff gels, whereas ovipositors can be inserted without such movements in soft gels. This indicates that reciprocal movements are needed in high-friction environments, presumably for buckling avoidance. Similar probing kinematics was observed in mosquitoes and suggested to occur in hemipterans. The increased knowledge on the functional morphology of multi-element insect probes may stimulate the development of new bioinspired minimally invasive tools.
