576 Invasive Stink Bugs and Related Species (Pentatomoidea)
lineatum (L.). This species also uses day length as a signal factor for the facultative winter adult dia-
pause induction. Laboratory experiments showed that the winter adult diapause of G. lineatum was con-
trolled by a long-day PhPR, which manifested itself at fairly high temperatures. The critical photoperiod
was 17 hours 15 minutes even at a constant temperature of 24°C (Musolin and Saulich 1996). Such a
high critical photoperiod induced diapause in the first generation of G. lineatum in the forest-steppe zone
and ensured the univoltine seasonal cycle, even though the required SET value of the population was
comparatively small (Musolin and Saulich 2001).
This conclusion was confirmed by an experiment under quasi-natural conditions. When, during the
experiment, the timing of nymphal development corresponded to the natural phenology of Graphosoma
lineatum in Belgorod Province of Russia (50°N), all individuals in the series entered diapause (Figure 12.7:
121826Temperature, °C22
18
1417
16Day length,h15
14
13
1995
199631%29%29%100%100%100%100%1996
***1995******15
10Number of
females
5
0
MayJune July August SeptemberFIGURE 12.7 Diapause induction in the Italian striped bug, Graphosoma lineatum, under quasi-natural conditions in
1995 and 1996 in Belgorod Province, Russia (50°N). Horizontal lines: series of the experiment. Arrows: dates of nymph
hatching in 1995; nymphs of second–fifth instars were transferred to quasi-natural conditions in 1996. Histograms: dates of
the final molt and the physiological status of females: light columns, active (i.e., reproductive, or nondiapausing) females;
shaded columns, diapausing females. Asterisks: onset of oviposition in the series of 1996. Curve: day length with half
the civil twilight ( 1 ); broken line: temperature ( 2 ). (From D. L. Musolin and A. Kh. Saulich, Entomologia Generalis 25:
255–264, 2001, with permission.)