Invasive Stink Bugs and Related Species (Pentatomoidea)

376 Invasive Stink Bugs and Related Species (Pentatomoidea)

and complete color change. If nymphs reach the adult stage too late in the season when the temperature
is already too low for their development (e.g., in late October or during November), adults may fail to
change body color and prepare properly for diapause, resulting in higher winter and/or spring mortality
(Musolin and Numata 2004, Musolin et al. 2010).
It is likely that only nonreproductive adults of the final summer generation that have not started repro-
duction can successfully overwinter. Eggs can hatch and nymphs are able to survive for several weeks in
the autumn or early winter if temperatures do not drop too much, but the nymphs cannot become adults
or survive until the spring. The majority of adults that begin reproduction in the summer or autumn
will die before or during overwintering, apparently being unable to switch from oviposition to diapause
(Musolin and Numata 2003b, Musolin et al. 2010; Dmitry L. Musolin and Daisuke Tougou, unpublished
data). However, in Japan, Kiritani (1963) observed a “black-spotted condition” in “females near to the
end of oviposition period” and was uncertain as to the origin of these black spots. Esquivel (2009) observed
what appeared to be a chorionated egg turning necrotic (or black-colored) within ovarioles of reproduc-
tive females during early fall in Central Texas (Esquivel 2009) and presumably this could be the “black-
spotted condition” reported by Kiritani (1963). Observations of the “black-spotted condition” in Texas
were noted at different localities within the production region and as recently as 2016 (Esquivel 2016b),
indicating that the condition can be widespread and suggest that reproductive females may be resorbing
eggs in preparation for overwintering. Additionally, Esquivel (2016b) expanded upon the composition
and potential cause(s) of the “black-spotted condition”.
Nezara viridula is a strong flier, and massive migrations pre- and postdiapause to and from the over-
wintering sites, respectively, comprise important phases of its seasonal cycle, although this has not been
studied thoroughly (Kiritani et al. 1966, Kiritani and Hokyo 1970, Gu and Walter 1989). Adults are
capable of sustained flight for as long as 12 hours under laboratory conditions (Kester and Smith 1984).
They can fly over long distances in the wild and have been caught on ships stationed up to 500 km from
the coasts (Hayashi et al. 1978, Gu and Walter 1989, Kiritani 2011). At least in the case of the prediapause
flight, experiments suggest that females fly as virgins (Gu and Walter 1989).

15

13

40

Air temp

erature, °C

35

30

25

20

15

10

5

-5

0

Da

y leng

th,

h

No. of female

s

11

9

35

30

25

20

15

10

5

0

JulAug SepJOctNovDecJan Feb MarAprMay Jun ul AugSep

FIGURE 7.11 Seasonal body color changes in female Nezara viridula under natural conditions in Osaka, Japan. The
experimental series corresponds to the late-season diapausing generation. Arrow marks the moment when the egg clusters
were transferred into outdoor conditions. The nymphs and males are not shown. The histogram shows the number and
color of females: dotted line, the total number of mating females; solid line, number of ovipositing females; light sections
of bars, green females; black sections of bars, brown/russet females; and shaded sections of bars, females with intermedi-
ate body color. The temperature is shown as the minimum and maximum daily values. (Modified from D. L. Musolin and
H. Numata, Ecological Entomology 28: 694–703, 2003b, with permission.)