Meeting Abstract
The proboscis of butterflies and moths consists of a pair of C-type fibers, called galeae, which are developed separately in the pupa and when the butterfly emerges from it, these two galeae are still separated. We observed that proboscis self-assembly is facilitated by discharge of saliva. In contrast with vertebrate saliva, butterfly saliva is not slimy and is an almost inviscid, water-like fluid. Butterfly saliva, therefore, cannot offer any viscoelastic adhesiveness. We hypothesize that the saliva meniscus is used by butterflies to bring and hold the galeae together while locking them in place. Theoretical analysis supported by X-ray micro-computed tomography on columnar liquid bridges suggests that both concave and convex liquid bridges are able to pull the galeae together[1, 2]. The image analysis of meniscus profiles confirms the model predictions. Experiments on sedated butterflies when the muscular action was diminished but saliva was present, show the crucial role of saliva meniscus in brining galeae together. Experiments on live butterflies and theory confirm that the adult insects are able to self-repair proboscises after separation of galeae. References 1. Zhang, C.Q., et al., Self-assembly of the butterfly proboscis: the role of capillary forces. Journal of the Royal Society Interface, 2018. 15(144): p. 20180229. 2. Why spit is key to building a butterfly. Nature, 2018. 560(7716): p. 2.
