Fluid secreted from tiny hairs on the feet of the European blowfly help it stick to surfaces via capillary action adhesion.

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“A study of fly footprints shows that the offending insect relies mainly on capillary forces generated by fluid secreted from its feet. Mattias Langer et al. used atomic-force microscopy to examine the adhesiveness of tiny puddles of foot fluid left by a fly, Calliphora vicina, as it walked across a glass slide. As the fluid evaporates, its stickiness decreases, showing that the fluid plays an important role in generating adhesion between foot and substrate. Adhesion measured in air was much stronger than that measured in an aqueous environment, indicating that capillary forces are mainly involved in the fly’s attachment mechanism.” (Hopkin 2004:756)

“The attachment pads of fly legs are covered with setae, each ending in
small terminal plates coated with secretory fluid. A cluster of these
terminal plates contacting a substrate surface generates strong
attractive forces that hold the insect on smooth surfaces. Previous
research assumed that cohesive forces and molecular adhesion were
involved in the fly attachment mechanism. The main elements that
contribute to the overall attachment force, however, remained unknown.
Multiple local force-volume measurements were performed on individual
terminal plates by using atomic force microscopy. It was shown that the
geometry of a single terminal plate had a higher border and
considerably lower centre. Local adhesion was approximately twice as
strong in the centre of the plate as on its border. Adhesion of fly
footprints on a glass surface, recorded within 20 min after
preparation, was similar to adhesion in the centre of a single
attachment pad. Adhesion strongly decreased with decreasing volume of
footprint fluid, indicating that the layer of pad secretion covering
the terminal plates is crucial for the generation of a strong
attractive force. Our data provide the first direct evidence that, in
addition to Van der Waals and Coulomb forces, attractive capillary
forces, mediated by pad secretion, are a critical factor in the fly’s
attachment mechanism.” (Langer et al. 2004:2209)

Journal article
Adhesion forces measured at the level of a terminal plate of the fly's setaProceedings of the Royal Society B: Biological SciencesOctober 21, 2004
M. G. Langer, J. P. Ruppersberg, S. Gorb

Journal article
Flies get a gripMichael Hopkin

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Urban Bluebottle BlowflyCalliphora vicinaSpecies

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