Nezara viridula ( L .) 373
7.4.4.2 Diapause-Associated Reversible Color Change in Adults
Nezara viridula has conspicuous body color polymorphism: more than ten, genetically determined, color
morphs of adults are recognized, with the most common being a completely green morph (G-type,
morph smaragdula F.) (Figure 7.1E–H; Yukawa and Kiritani 1965; Kiritani 1970, 1971; Hokkanen
1986; Ohno and Alam 1992). In addition to this genetically controlled adult body color polymorphism,
N. viridula shows an interesting example of a reversible seasonal adult color change (seasonal poly-
phenism; also see Figure 11.17 and Chapters 11 and 12). With the possible exceptions of a recently
observed blue morph in Brazil (Figure 7.1G; Antônio R. Panizzi, personal communication) and a black
morph in North America (Figure 7.1H; Esquivel et al. 2015), adults of all other genetic color morphs
turn gradually russet or reddish-brown when they experience diapause-inducing conditions (Figure
7.1D and Figure 11.17; Harris et al. 1984, Seymour and Bowman 1994, Musolin and Numata 2003a,
Musolin 2012). This russet color is physiologically controlled and reversible (Yukawa and Kiritani 1965,
Musolin and Numata 2003a, Musolin et al. 2007). Adult diapause termination, the resumption of active
development, and the beginning of postdiapause reproduction are associated with a gradual reversion to
the original body color (see below). This color change is conditioned by processes not in the cuticle but
in the underlying epidermal cells and involves the pigment erythropterin (Gogala and Michieli 1962,
1967). Although erythropterin occurs in both nondiapausing (green, yellow, and others) and diapausing
(reddish-brown or russet) adults, in the former it exists in aqueous solution, whereas in the latter it is
predominantly crystalline and deep red (Harris et al. 1984). It has been noted that the intensity of the
russet color is somewhat stronger in females than males (Kiritani and Hokyo 1970). Oxygen consump-
tion also is much lower in russet-colored adults than in green adults (Michieli and Žener 1968). The
reddish-brown winter coloration of adults apparently functions as a camouflage in the hibernacula. It
seems likely that the cryptic role of the seasonal color change has never been studied experimentally in
this species, whereas this type of adaptation is well known in several other species of true bugs and other
insect taxa (Fuzeau-Braesch 1985, Saulich and Musolin 2012). In addition to camouflage, this seasonal
adult body color change might also be important for thermoregulation during the period of diapause
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Photophase, hIncidence of diapause,%FIGURE 7.8 Photoperiodic response curves for diapause induction in females and males of Nezara viridula. Solid line
and closed circles, females at 25°C; solid line and open circles, males at 25°C; dashed line and closed triangles, females at
20°C; dashed line and open triangles, males at 20°C (for L:D 12:12 and L:D 13:11 at 25°C, the results of three replications
are also shown as closed squares, females; open squares, males). Shaded area shows a range of critical day length inducing
diapause in 50% of individuals. (From D. L. Musolin and H. Numata, Physiological Entomology 28: 65–74, 2003a, with
permission.)