DOI: 10.5061/dryad.x3ffbg7hg
title: Drosophila glue protects from predation

description: Animals can be permanently attached to a substrate in aerial environments
 at certain stages of their development. Pupa adhesion has evolved multiple
 times in insects and is thought to maintain the animal in a place where it
 is not detectable by predators. Here, we investigate whether pupa adhesion
 in Drosophila can also protect the animal by preventing potential
 predators from detaching the pupa. We measured the adhesion of Drosophila
 species sampled from the same area and found that pupa adhesion varies
 among species, which can be explained by different glue production
 strategies. Then, we compared attached and manually detached pupae in both
 field and laboratory assays to investigate the role of pupa adhesion to
 prevent predation. First, we found that attached pupae remain on site 30 %
 more than detached pupae in the field after three days, probably because
 they are less predated. Second, we observed that attached pupae are less
 efficiently predated by ants in the laboratory: they are not carried back
 to the ant nest and more ants are needed to consume them onsite. Our
 results show that pupa adhesion is crucial for Drosophila fly survival and
 can prevent the animal from being taken away by predators.
description: <strong>Figure S1. Distribution of the buckets in Bois de
 Vincennes</strong>. Each circle represents one bucket. Dashed lined
 circles indicate unused buckets and solid lined circles buckets used for
 the experiment. The number in the circle indicates the ID of the bucket.
 Crosses indicate the location of the trees. Orientation of the location is
 indicated in the top left corner. <strong>Table
 S1</strong>. <strong>List of Drosophila flies collected in
 Bois de Vincennes</strong>. The number corresponds to the total
 number of individuals collected at each site. Traps were emptied twice,
 two days and five days after traps were set up in the field. GPS
 coordinates are shown for each trap and for the compost.
 <strong>Table S2</strong>. <strong>Adhesion
 force and pupa-substrate interface measurements</strong>. Results of
 the adhesion assay performed on pupae from <em>D. suzukii, D.
 simulans and D. hydei </em>strain originating from Vincennes.
 Sample_ID column corresponds to a unique identifier for each pupa,
 Temperature_assay, Humidity, Pressure_mba indicate respectively the room
 temperature (°C), the room humidity (%) and the atmospheric pressure (mba)
 at the moment of the assay. date_measurement and time_measurement
 correspond to the day and hours of the assay. date_substrate and
 time_substrate correspond to the day and hours at which larvae were put on
 the substrate. force_detachment_mN corresponds to the maximum force
 reached during the experiment in mN. Comment_on_this_sample reports
 particular observations:  the pupa did not detach from the substrate
 (“not_detached”), the pupal case broke during the assay (“cuticle_broke”)
 or nothing special happened during the assay (“ok”). Area_px corresponds
 to the pupa-substrate contact surface measured in pixel and scale_px,
 scale_mm correspond respectively to the scale present on the picture in
 pixel and mm. <strong>Table S3</strong>.
 <strong>Pupal size measurement</strong>. Measurements of the
 size of pupae of<em> </em><em>D. simulans, D. suzukii,
 D. hydei</em>. ID column corresponds to a unique identifier for each
 pupa. Area corresponds to the area obtained by measuring the contour of
 the pupa in pixel. scale_px and scale_mm are defined as in Table
 S2. <strong>Table S4</strong>.
 <strong>Pupal count in the field experiment</strong>. Results
 of the experiment performed in the field. bucket_ID column corresponds to
 a unique identifier for each bucket. Orientation_C and Orientation_NC
 give, respectively, the orientation of attached and detached pupa within
 the bucket. Count_C and Count_NC indicate, respectively, the number of
 attached and detached pupa in a dish. Time indicates the time at which
 pupae were counted: t0 after 0h (8 September 2020, day 1 morning, at 11
 am) t1 after 6h30 (day 1 PM), t2 after 22h30 (day 2 AM), t3 after 31h (day
 2 PM), t4 after 47h (day 3 AM), and t5 after 54h (day 3 PM).
 <strong>Table S5</strong>. <strong>Animals
 observed in the dishes during the experiment with half-buried buckets in
 Bois de Vincennes</strong>. The number indicates the number of
 dishes where the respective animals were observed. In total, 56 dishes
 were examined at each time point. <strong>Table
 S6</strong>. <strong>Ant count during predation assay in the
 laboratory</strong>. The number indicates the number of ants
 observed in direct contact with the pupa at each time point. The column
 “X_Y” corresponds to the count over one experiment with the ant colony X
 at the trial Y. <strong>Table S7</strong>.
 <strong>Results table of the predation assay in the
 laboratory</strong>. Each row corresponds to the description of the
 experiment for one pupa. condition column indicates the initial state of
 the pupa (“attached” or “detached”), strategies indicates whether the pupa
 was brought to the nest over the duration of the experiment (“to_nest”) or
 was never brought to the nest and consumed outside the nest (“on_site”).
 Time corresponds to the time at which the pupa was brought to the nest or
 fully consumed outside the nest in min. max_ant corresponds to the maximum
 number of ants observed in contact with the pupa over the duration of the
 experiment. orientation indicates whether the pupa was initially on the
 left or on the right side of the glass slide at the beginning of the
 experiment. first_ant corresponds to the time in min at which the first
 interaction between the pupa and an ant is observed. max_ant_at_first_done
 corresponds to the maximum number of ants observed in direct interaction
 with the pupa from the beginning of the experiment to the time when the
 first pupa is brought to the nest or fully consumed outside the
 nest. <strong>Table S8</strong>.
 <strong>Pupal count in the field experiment</strong>. Same as
 Table S4 except that one line corresponds to one individual. Status is
 either 0 (pupa still present) or 1 (pupa disappeared).
 <strong>R script</strong>.
 <strong>Drosophila_glue_predation.R</strong>: R script used to
 prepare the figures and run the statistical tests.
 <strong>pupa_prints</strong>: Folder containing
 pictures of the prints left by the pupae on glass slides after detachment
 during our adhesion assay force measurements.
 <strong>pupal_size</strong>: Folder containing the
 pictures of pupae used to measure the size of the pupae of the different
 species.
 <strong>Pictures_Videos_Vincennes</strong>: Folder
 containing pictures and videos taken during and after the experiments in
 the field.
 <strong>Pictures_Videos_predation_lab</strong>:
 Folder containing pictures and video of the predation assays in the
 laboratory