Diapause in Pentatomoidea 535
their host plant. For overwintering, adults change body color to orange, which also is adaptive because
leaves are reddish/brown in the autumn and the litter in which the adults overwinter is dark. In spring,
both females and males change body color and starting at this moment the trajectories of body color
begin to differ between the sexes. Males turn dark green and die after copulation. Females, on the other
hand, turn light green, and their body color corresponds to the color of the lower surfaces of leaves where
females guard their only egg cluster; they remain with the resulting brood until the nymphs reach the last
instar. Only after this prolonged guarding, females turn dark green and then either die or probably over-
winter again. It has been speculated that this seasonal polyphenism (or at least one of its phase, namely,
light green to dark green transition) is not regulated by day length but, rather, linked to sexual maturation
and copulation, as this transition is characteristic only of females. The control mechanism of body color
change in this species still needs to be determined. Nevertheless, the whole pattern looks very adaptive
and linked to parental care, a behavioral strategy well known in acanthosomatids and some other true
bugs (Cobben 1968, Tallamy and Wood 1986, Kudo 2006).
In the case of seasonal morphological polyphenism, seasonal forms (sometimes called seasonal
morphs) can differ morphologically. For example, the bugs can have different shapes of spines on
the pronotum as in the pentatomids Euschistus tristigmus tristigmus (McPherson 1975a,b), Oebalus
ypsilongriseus (Vecchio et al. 1994, Panizzi 2015), Euschistus heros (Mourâo and Panizzi 2002), and
Dichelops melacanthus (Chocorosqui and Panizzi 2003). These are the examples of irreversible seasonal
polyphenism.
1513Day length,h1192540Air temperature, °C35
30
25
20
15
10
5
0
20 –5
15
10
5
025
2035
3015
No. of females10
5JulAug SepJOct NovDecJan Feb Mar AprMay Jun ul AugSep0FIGURE 11.18 Seasonal body color changes in female of the southern green stink bug, Nezara viridula, under natural
conditions in Osaka, Japan (34.7°N). The upper experimental series corresponds to the mid-summer reproductive (i.e.,
nondiapause and directly breeding) generation; the lower series, the late-season diapausing generation. Arrow marks the
moment when the egg clusters were transferred into outdoor conditions to start each experimental series. The nymphs
and males are not shown. The histogram shows the number and color of females as follows: Light sections of bars: green
females; shaded sections of bars: females with intermediate body color; black sections of bars: brown/russet females.
Dotted line: the total number of mating females; solid line: that of ovipositing females. The temperature is shown as the
minimum and maximum daily values. (Modified from D. L. Musolin and H. Numata. Ecological Entomology 28: 694–703,
2003, with permission.)