Data from: Mechanisms of ovipositor insertion and steering of a parasitic wasp

Drilling into solid substrates with slender beam-like structures is a
mechanical challenge, but is regularly done by female parasitic wasps. The
wasp inserts her ovipositor into solid substrates to deposit eggs in
hosts, and even seems capable of steering the ovipositor while drilling.
The ovipositor generally consists of three longitudinally connected valves
that can slide along each other. Alternative valve movements have been
hypothesized to be involved in ovipositor damage avoidance and steering
during drilling. However, none of the hypotheses have been tested in vivo.
We used 3D and 2D motion analysis to quantify the probing behavior of the
fruit-fly parasitoid Diachasmimorpha longicaudata (Braconidae) at the
levels of the ovipositor and its individual valves. We show that the wasps
can steer and curve their ovipositors in any direction relative to their
body axis. In a soft substrate, the ovipositors can be inserted without
reciprocal motion of the valves. In a stiff substrate, such motions were
always observed. This is in agreement with the damage avoidance hypothesis
of insertion, as they presumably limit the overall net pushing force.
Steering can be achieved by varying the asymmetry of the distal part of
the ovipositor by protracting one valve set with respect to the other. Tip
asymmetry is enhanced by curving of ventral elements in the absence of an
opposing force, possibly due to pretension. Our findings deepen the
knowledge of the functioning and evolution of the ovipositor in
hymenopterans and may help to improve man-made steerable probes.