Invasive Stink Bugs and Related Species (Pentatomoidea)

522 Invasive Stink Bugs and Related Species (Pentatomoidea)

11.5.1 Spontaneous Termination of Winter Diapause

This type of termination of winter diapause is based on endogenous (horotelic) processes and may pro-
ceed under the same conditions under which diapause was induced. Spontaneous diapause termination
is thought to be most important in species with a weak diapause, which generally is typical of insects
of tropical and subtropical origin. Because the conditions never remain constant in most parts of the
Earth, true spontaneous diapause termination can be observed only under stable laboratory conditions.
The possibility of this type of winter diapause termination under constant conditions has been shown in
laboratory experiments for many heteropterans, including the stink bugs Carbula humerigera (Kiritani
1985b), Plautia stali (Kotaki 1998a,b), Nezara viridula (Musolin et al. 2007), and others.
Spontaneous diapause termination usually follows a prolonged period of diapause development, with
the timing of diapause termination varying between individuals. For example, Musolin et al. (2007)
showed the timing of postdiapause oviposition between the earliest and the latest females of Nezara
viridula in different short-day regimes at 25°C varied from 106 days (photophase 13 hours; Figure
11.13C) to 158 days (photophase 10 hours; Figure 11.13A), whereas in the nondiapausing females the
range of variation was only 43 days at the same temperature (photophase 14 hours; Figure 11.13D).
Under natural conditions, the difference in the timing of oviposition after overwintering between the
earliest and the latest females was only 23 days (Musolin et al. 2007). These results demonstrate that
rates of spontaneous diapause termination vary greatly between individuals.

5 4 3 2 1 0 5 4 3 2 1 0 5 4 3 2 1 0

25

20

15

10

5

(^0020406080100120140160180200220240260280300320340360)
Days after adult emergence
Numb
er of female
s
A
B
C
D
L:D 10:14
L:D 12:12
L:D 13:11
L:D 14:10
FIGURE 11.13 Effect of photoperiod on the preoviposition period in females of the southern green stink bug, Nezara
viridula, from Osaka, Japan (34.7°N) at 25°C. Nymphs were reared to adults and then maintained under constant experi-
mental conditions (From D. L. Musolin, K. Fujisaki, and H. Numata, Physiological Entomology 32: 64–72, 2007, with
permission.)