582 Invasive Stink Bugs and Related Species (Pentatomoidea)
response of the Osaka population was about 13 hours 30 minutes at 25°C. The day length (with half the
civil twilights) in Osaka at the beginning of September is 13 hours; this value determined the onset of
facultative winter adult diapause (Nakamura and Numata 2006).
Many species of true bugs studied in this region of Japan have similar critical photoperiods of winter
diapause induction and produce three generations per season (see Section 12.5.1 below). Based on this,
the cited authors assumed that Dolycoris baccarum also developed in three generations in the Osaka
region, although, according to other data (Kobayashi 1972), this species has a bivoltine seasonal cycle
there.
The critical photoperiod for the Hokkaido population was about 16 hours, which permitted develop-
ment of two complete generations (Figure 12.12). The difference in the critical photoperiod of dia-
pause induction between the populations from Osaka and Hokkaido was more than 2 hours, indicating
a clinal geographic variation (Figure 12.12). The critical photoperiod changed by about 1 hour every
5 degrees of latitude, similar to what had been determined earlier for many insect species (Danilevsky
1961, Saulich and Volkovich 2004). According to the earlier cited data of Perepelitsa (1971) for Voronezh
and Krasnodar, the critical day length of European populations also varied within 1 hour per 5 degrees
of latitude.
The temperature-related variation of the long-day PhPR of diapause induction usually is manifested
in the following way: the proportion of diapausing individuals decreases in all the photoperiods as the
temperature rises. Such variation was observed in the European populations of Dolycoris baccarum
from Norway (Conradi-Larsen and Sømme 1973) and The Czech Republic (Hodek and Hodková 1993).
By contrast, in the Japanese populations, the number of diapausing individuals decreased noticeably
only under the long-day conditions L:D 16:8 whereas at short-day conditions L:D 12:12, the number of
diapausing bugs did not decrease even when the temperature rose to 27.5°C and 30°C (Figure 12.13).
The effect of the temperature was noticeable only in the duration of diapause, which was much shorter
at 30°C than at 25°C in the bugs of both populations under the short-day conditions (Nakamura and
Numata 2006).
Stink bugs of the genus Aelia have been well studied because of their economic importance as cereal
pests. In particular, the development of two species, A. acuminata (L.) and A. sibirica Reuter, was
studied in the north of Kazakhstan (Kustanai Province, 53°N) where both species can produce two
generations per vegetative season (Burov 1962). Despite slight differences in the parameters of the PhPR
of diapause induction (Figure 12.14), the seasonal cycles of the two species are noticeably different.
A. sibirica shows a greater tendency for univoltinism, with more than 30% of adults of the first genera-
tion forming winter adult diapause even in the most favorable years.
10050AB
L:D 16:8 L:D 12:120
20 25 30 20 25 30
Temperature, °CIncidence of diapause,%FIGURE 12.13 The effect of temperature on winter diapause induction in the populations of the sloe bug, Dolycoris
baccarum, from Osaka (34.7°N) and Hokkaido Island (44.2°N), both in Japan, under long-day (A) and short-day (B) condi-
tions. Nymphs were reared to adults and then maintained at four different temperatures (indicated under the horizontal
axis) under two constant photoperiodic conditions – long day L:D 16:8 and short day L:D 12:12. Open circles, females
of the Osaka population; closed circles, males of the Osaka population; open triangles, females of the Hokkaido popula-
tion; closed triangles, males of the Hokkaido population. (From K. Nakamura and H. Numata, Applied Entomology and
Zoology 41: 105–109, 2006, with permission.)