Invasive Stink Bugs and Related Species (Pentatomoidea)

524 Invasive Stink Bugs and Related Species (Pentatomoidea)

The interaction of spontaneous and induced processes during diapause termination were demonstrated
in two studies using Podisus maculiventris that originated from Missouri, the United States of America
(about 38°N). In the first experiment, diapause induction, termination, and postdiapause oviposition were
studied after exposure of the bugs to different photoperiodic and temperature conditions (Figure 11.14;
Chloridis et al. 1997). When females were reared from egg to adult and then maintained at long-day
conditions (L:D 16:8) and 23°C and remained under the same conditions further, all of them were non-
diapause and soon started oviposition (curve A). Basically, the same was recorded when females were
reared from egg to adult and then maintained under the same long-day conditions (L:D 16:8) and 23°C
but were transferred to short-day conditions (L:D 8:16) on day 13 after the final molt: these females were
reproductive and did not stop oviposition at least during 27 days following the transfer from long-day
to short-day conditions (curve B). On the contrary, all females reared from egg to adult and then main-
tained under short-day conditions (L:D 8:16) at 23°C entered diapause (curves C, D, and E). As a result
of spontaneous diapause termination under constant short-day conditions (L:D 8:16) at 23°C (curve C),
the females started laying eggs on day 47, which indicated that the diapause formed at the photoperiod
L:D 8:16 and 23°C was not very deep and stable. Exposure to cold under the same short-day conditions
(4°C for 10 days; curve E) hastened the onset of the postdiapause oviposition and increased the fraction
of ovipositing females as compared to those in the trial in which the females were kept under constant
short-day conditions at 23°C without any cold treatment (curve C). However, even on day 130, the frac-
tion of ovipositing females was only slightly over 40% (curve E). A much greater diapause terminating
effect was observed after consecutive action of cold (10 days at 4°C and darkness) and long-day condi-
tions (L:D 16:8) and 23°C (curve D): oviposition started on day 25 (i.e., 10 days of low-temperature treat-
ment plus 15 days of reproduction stimulating conditions), and all the females terminated diapause by
day 70. These results show that adults of P. maculiventris remain sensitive to day length during winter
diapause, which is a prerequisite for its photoperiodic termination. Moreover, day-length sensitivity is
preserved even after exposure to cold.

100

A

16:8

B

16:8

D

8:16

4°C

16:8

E

8:16

C

8:16

4°C

(^) 8:16
8:16
80
60
40
20
0
0102030405060708090 100 110 120 130
Age, days
Numb
er of females la
ying eggs
, %
FIGURE 11.14 Oviposition dynamics in females of the spined soldier bug, Podisus maculiventris, under different pho-
toperiodic conditions at 23°C (if otherwise not indicated). A – females reared from eggs to adults and then maintained at
long-day conditions (L:D 16:8); B – females reared from eggs to adults and then maintained at long-day conditions (L:D
16:8); on day 13, after the final molt, females were transferred to short-day conditions (L:D 8:16); C – females reared from
eggs to adults and then maintained at constant short-day conditions (L:D 8:16); D – females reared from eggs to adults and
then maintained at short-day conditions (L:D 8:16); then on day 13, after the final molt, females were transferred to 4°C and
darkness for 10 days, then to long-day conditions (L:D 16:8); E – females reared from eggs to adults and then maintained
at short-day conditions (L:D 8:16); then on day 13, after the final molt, females were transferred to 4°C and darkness for
10 days, then to short-day conditions (L:D 8:16). The laboratory culture originated from Missouri, the United States of
America (about 38°N). (From A. S. Chloridis, D. S. Koveos, and D. C. Stamopoulos, Entomophaga 42: 427–434, 1997,
with permission.)