Data from: "Alternative phenotypes within mating systems" in The evolution of insect mating systems

Insects were for a long time considered simple organisms with unvarying
behavioural repertoires, incapable of complicated behavioural responses to
changing environments and/or social conditions. However, nothing could be
further from the truth; phenotypic plasticity is widespread in insect
development, life history, physiology, and behaviour (Whitman and
Ananthakrishnan 2009). Plastic responses to environmental and social
conditions are actually central to the remarkable adaptability of insects,
and have played a crucial role in their evolutionary histories (Moczek
2010; Simpson et al. 2011). Moreover, phenotypic plasticity in insects is
not merely restricted to simple responses in metabolism or activity to
abiotic factors such as temperature, but can be extremely elaborate, an
illuminating example of which is the learning ability of honeybees (Giurfa
2007; Hammer and Menzel 1995; Menzel 1993; Menzel and Muller 1996). Insect
mating systems are no exception to this pattern. This chapter explores the
intrasexual variation in behaviours and morphologies found in insect
mating systems. More specifically, we focus on the evolution of the
alternative means by which individuals obtain fertilizations, generally
referred to as ‘alternative mating tactics’, or ‘alternative mating
phenotypes’ (AMPs). The first studies to describe what we can interpret
today as cases of AMPs in insects date back to at least the 1930s (Salt
1937), but it was only in the 1970s that the number of studies reporting
this phenomenon started to accumulate. In 1983, when the classic examples
of AMPs in digger bees and scorpionflies were reviewed by Thornhill and
Alcock (1983), approximately 50 cases of AMPs in insects were already
known, a number that has now surpassed the 200 mark. Here, we review the
theoretical and empirical advances that have been made in this area since
Thornhill and Alcock’s volume. We start by describing two illustrative
systems in detail, gryllid field crickets and onthophagine dung beetles.
These two groups were chosen because their reproductive biology is well
known, and because the contrasting degrees of behavioural plasticity and
morphological specialisation between alternative phenotypes in these two
groups illustrate the diversity of AMPs that has evolved in insects. We
then discuss the genetic models that have been proposed to account for the
evolution and maintenance of such dimorphisms, before reviewing the
occurrence of AMPs in insects more generally. Finally, we discuss the
relatively limited evidence for AMPs in female insects, a somewhat new and
very promising area for future research.