Insects produce a variety of adhesives for diverse functions such as locomotion, mating, egg or pupal anchorage to substrates. Although they are important for the biology of organisms and potentially represent a great resource for developing new materials, insect adhesives have been little studied so far. Here, we examined the adhesive properties of the larval glue of D. melanogaster. This glue is made of glycosylated proteins and allows the animal to adhere to a substrate during metamorphosis. We designed an adhesion test to measure the pull-off force required to detach a pupa from a substrate and to evaluate the contact area covered by the glue. We found that the pupa adheres with similar forces to a variety of substrates (with distinct roughness, hydrophilic and charge properties). We obtained an average pull-off force of 217 mN, corresponding to 15 500 times the weight of a pupa and adhesion strength of 137-244 kPa. Surprisingly, the pull-off forces did not depend on the contact area. Our study paves the way for a genetic dissection of the components of Drosophila melanogaster glue that confer its particular adhesive properties.

Borne_2020_glue_table_S1.csv - Table S1. Raw dataset of adhesion measurements and measurement conditions.

glue-adhesion-script.R - R script used to prepare the figures and run the statistical tests.

Supplementary_files.pdf - PDF containing other Supplementary Information:

• Table S2. Contact angle measurements (°) for the different substrates. Contact angles were measured for each substrate. All the measurements were done before the pull-off force measurements except for PLL-PEG-coated glass.
• Figure S1. Force in function of (A) black area, (B) green area and (C) red area. Each dot represents one print on glass-type substrates. The grey lines represent the linear regressions: (A) r²= 0.01168, y= 257.69 - 46.03x, p=0.144 ; (B) r²= -0.009391, y= 218.05 + 13.73x, p=0.7793 ; (C) r²= 0.004791, y= 279.36 - 19.97x, p= 0.2369; where r² is the adjusted r².