Data from: Anticipatory flexibility: larval population density in moths determines male investment in antennae, wings and testes

Developmental plasticity provides individuals with a distinct advantage
when the reproductive environment changes dramatically. Variation in
population density, in particular, can have profound effects on male
reproductive success. Females may be easier to locate in dense
populations, but there may be a greater risk of sperm competition. Thus,
males should invest in traits that enhance fertilization success over
traits that enhance mate location. Conversely, males in less dense
populations should invest more in structures that will facilitate mate
location. In Lepidoptera, this may result in the development of larger
antennae to increase the likelihood of detecting female sex pheromones,
and larger wings to fly more efficiently. We explored the effects of
larval density on adult morphology in the gum-leaf skeletoniser moth,
Uraba lugens, by manipulating both the number of larvae and the size of
the rearing container. This experimental arrangement allowed us to reveal
the cues used by larvae to assess whether absolute number or density
influences adult responses. Male investment in testes size depended on the
number of individuals, while male investment in wings and antennae
depended upon larval density. In contrast, the size of female antennae and
wings were influenced by an interaction of larval number and container
size. This study demonstrates that male larvae are sensitive to cues that
may reveal adult population density, and adjust investment in traits
associated with fertilization success and mate detection accordingly.