The development and evolution of butterfly wing patterns:
finding the primitive pattern
Fred Nijhout
Department of Biology
Duke UniversityDurham, NC 27708
hfn@duke.edu

Synopsis: The color patterns of butterflies and moths constitute a highly evolved system ofvisual communication used in sexual signaling, camouflage, warning, territoriality andmimicry. These patterns are based on extensive modifications of a groundplan of three pairsof bands. The ancestors of this pattern can be found as far back as the dragonflies, which
are among the first winged insects, and model simulations will illustrate how this could havehappened.
Outline: The development and evolution of butterfly wing patterns have been extensively
studied over the past 30 years. Much of our understanding of the structure of these color
patterns derives from the classical work of Schwanwitch (1924) and Süffert (1927). Theseauthors independently derived the diversity of color patterns in the butterfly Family
Nymphalidae, from a common ”groundplan” composed of three parallel pairs of bands thatrun from the anterior to posterior margin of the wing. Each pair of bands has a characteristicpigmentation pattern and is called a symmetry system because the pigments of the bands
mirror each other. Subsequent work by these authors and their associate showed that the“nymphalid groundplan” (Figure 1) applies widely to other Families of butterflies and to
many moths as well.

Figure 1. The Nymphalid Groundplan iscomposed of 3 sets of bands called thebasal-, central- and border- symmetry
systems. In some butterflies and moths thebands are un-interrupted, as in the left
panel, but in most cases the bands aredisrupted by the vein system (as in the rightpanel), which compartmentalizes thepattern into semi-independent
developmental units (after Nijhout, 1991).

A long-standing question in this field is whether the Nymphalid Groundplan somehow
represents the primitive butterfly wing pattern from which all others were derived. The
butterflies are phylogenetically within the moths, so if there is a primitive pattern of
Lepidoptera, it needs to be sought among the moths. Recently, Schachat and Brown (2016)
studied the color patterns of the Micropterigidae, the most basal group of moths, anddeduced that their color patterns were based on a system of 5-6 parallel bands. In many
moths and butterflies the crossbands are interrupted by the wing veins and appear as a rowof spots, and it is still an open question whether bands arose from rows of spots or whetherrows of spots came from broken bands.
In my presentation I will show that the primitive color pattern from which the mothpatterns evolved arose long before the evolution of the Lepidoptera. Color patterns of thecaddis flies (Trichoptera) and scorpion flies (Mecoptera) all resemble those found in thebasal moths. I will show that these patterns are all based on variations on a set of 6 parallel
bands, and that this basic patterning system can be found in the earliest winged insects,
represented today by the dragonflies (Odonata).
A simple reaction-diffusion system can readily generate three symmetry systems, that canbe visualized as either 3 pairs of bands or 6 identical bands (e.g. the yellow stripes in Figure2).

Figure 2. Pattern of threesymmetry systems formed
by a substrate-depletion
model of reactiondiffusion.

I will show that from this banding system, a lateral inhibition mechanism can, in turn,generate much of the diversity of spotting and banding patterns that we see in thedragonflies and other patterned insect wings, including the Lepidoptera.
References:Nijhout, H. F. (1991). Development and Evolution of Butterfly Wing Patterns. Washington D.C.
Smithsonian Press.
Schachat, S.R. and Brown, R.L., 2016. Forewing color pattern in Micropterigidae (Insecta:Lepidoptera): homologies between contrast boundaries, and a revised hypothesis for theorigin of symmetry systems, BMC Evolutionary Biology. 16, 116.
Schwanwitsch, B. N. (1924). On the groundplan of the wing-pattern in nymphalids and certain otherfamilies of rhopalocerous Lepidoptera. Proceedings of the Zoological Society of London B, 34,509–528.
Süffert, F. (1927). Zur vergleichende Analyse der Schmetterlingszeichnung. Biologisches Zentralblatt,47, 385–413.