Drosophila glue protects from predation

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.