584 Invasive Stink Bugs and Related Species (Pentatomoidea)
activity of A. fieberi is long enough for this species to produce two complete generations. Adults of the
first generation reproduce actively in summer and die after oviposition. Adults of the second generation
form winter diapause in autumn under the influence of short-day conditions (Nakamura and Numata
1997). With such a seasonal cycle, there seems to be no need for repeated overwintering; therefore, res-
toration of photoperiodic sensitivity becomes unnecessary.
According to laboratory data, the critical photoperiod of diapause induction of Aelia fieberi at 25°C is
14 hours 30 minutes; it determines winter diapause induction as early as the beginning of August, when
the temperature conditions would still be favorable for further activity and development of the third gen-
eration. Experiments carried out under field conditions showed that the nymphs developed successfully
under field temperatures until October, and the adults that emerged under such conditions could over-
winter successfully. Thus, the temperature of the autumn months did not suppress development of the
potential third generation. However, it was determined that voltinism of this species also was controlled
by a trophic factor: the seeds that ripened late proved to be unsuitable for feeding of the nymphs. As a
result, under the influence of natural selection, A. fieberi in central Japan produces only two generations
per season, whereas the day length remains the principal control cue of its seasonal cycle (Nakamura
and Numata 1997).
Aelia rostrata Boheman also has a facultative winter adult diapause (Şişli 1965), but its seasonal cycle
studied in Turkey clearly differs from those of other species of the genus Aelia. At the beginning of May,
when the temperature rises above 20°C, the overwintered adults migrate from their mountain overwin-
tering sites onto the plains, mostly to cereal fields. After 10–15 days of intense feeding, they mature and
start oviposition. Preadult development of the new (first) generation takes about a month, so that young
adults of the summer generation appear in the second half of June and enter summer diapause. In the
study region, A. rostrata produces only one generation per season (Babaroğlu and Uğur 2001). As the
cereals ripen and the summer temperatures rise, the young adults migrate to the mountain estivation (i.e.,
summer diapause) quarters positioned at 1,200–2,000 meters a.s.l., where they gradually enter hiberna-
tion (i.e., winter diapause) with the onset of cold in autumn. In other species having a similar seasonal
cycle, namely Dolycoris baccarum (Krambias 1987) and shieldbacked bugs of the family Scutelleridae
(Arnoldi 1947, Brown 1962), the summer and winter diapauses are separated by short active periods dur-
ing which time the adults fly short distances and migrate from one dormancy place to another (Krambias
1987). There is no evidence yet of such migrations between summer and winter diapauses in A. rostrata
(Cakmak et al. 2008).
12.3.2 The Strictly Bivoltine Seasonal Cycle
The strictly bivoltine seasonal cycle can be regarded as a special case of multivoltinism, characterized by
development of only two generations per year, one in spring (or early summer) and one in autumn (or late
summer). The two periods of activity usually are separated by summer diapause (i.e., estivation), which
ensures survival during the unfavorable period in mid-summer with high temperatures and scarce food.
This happens every year, even though the temperature resources would usually be sufficient for a greater
number of generations. Obligate or facultative estivation occurs in summer under the conditions of high
temperatures and long day. This frequently is observed in species living in the tropical and subtropical
belts and is typical of the inhabitants of deserts and semi-deserts, even though it is quite common in the
temperate latitudes as well. Estivation can be linked to any stage of development, from egg to adult, but
the estivating stage is strictly species-specific (Masaki 1980; see Chapter 11 for details).
This pattern of seasonal development first was studied in the cabbage moth, Mamestra brassicae L.
(Lepidoptera, Noctuidae), which has only two generations even in the extreme south of Japan, although,
theoretically, it would be able to produce up to six generations per season in that region (Masaki and
Sakai 1965).
Among the pentatomoids, an example of a species with a strictly bivoltine seasonal cycle is the
Oriental green stink bug, Nezara antennata Scott.
There are two species of the genus Nezara distributed in Japan: N. antennata and N. viridula. Of
these, N. antennata is known only from Asia (Hokkanen 1986, Rider 2006; see Chapter 7). This spe-
cies is widespread in Japan, its range covering the islands of Okinawa, Kyushu, Shikoku, Honshu, and