Aerial egg transfer using a Velcro®-like catching mechanism in stick insect oviposition

The trade-off between offspring quality and quantity can demand substantial resources and is a major force shaping reproductive evolution. Stick and leaf insects (Phasmatodea) produce hard-shelled eggs exhibiting remarkable phenotypic diversity. Their oviposition technique is considered the main factor influencing the egg shape and its surface structures. Evolutionary divergence from the ancestral egg-dropping technique to various derived modes of oviposition gave rise to a wide range of adaptations. We discovered that the burr-like surface structures on the eggs of Orestes draegeri (Heteropterygidae: Dataminae) evolved to form a reversible mechanical interlocking with the antennae. We revealed this combination to be specialized for its remarkable oviposition technique and provide the first high-speed recordings of this stereotypic behaviour. To deposit the egg in a previously dug hole, the female throws the egg in a quick and acrobatic launch-and-catch movement from the abdomen to the antennae. The egg “hairs” end in a grappling hook-like structure that interlocks with specific mushroom-shaped cuticular protuberances on the female antennae. The peculiar technique adopted by O. draegeri represents a refined trade-off between the cryptic behaviour of Phasmatodea and finding the best conditions for the development of their offspring. Furthermore, we characterised the attachment performance of this mechanism and revealed the first example of a hook and mushroom probabilistic fastener in phasmids. Our study underscores the heterogeneity of oviposition techniques in insects, especially in Phasmatodea, and demonstrates remarkable morphological and behavioural adaptations for targeted oviposition.