Invasive Stink Bugs and Related Species (Pentatomoidea)

516 Invasive Stink Bugs and Related Species (Pentatomoidea)

Individuals of the first generation feed on wild crucifers (e.g., brown mustard) that die out before early
summer. The resulting adults emerge in mid-June and most enter diapause. Because the cultivated cru-
cifers (such as radish and cabbage) remain green much longer, most of the first-generation adults feeding
on them are reproductively active and give rise to individuals of the second generation, which become
adults at the end of summer and form the overwintering population (Ikeda-Kikue and Numata 2001). To
determine the role of individual factors in control of seasonal development of this species, the nymphs
were reared to adults and then maintained on two different diets (i.e., leaves and seeds of rape, Brassica
napus L.) under experimental conditions similar to those in the natural environment (Figure 11.8).
The nymphs of Eurydema rugosa developed in June under long-day conditions synchronously on the
two diets. Most adults of both sexes that molted in July and were maintained on rape leaves remained
physiologically active; the females copulated and laid eggs and gave rise to the second generation. By
contrast, nearly all the adults that molted at the same time but were maintained on rape seeds entered
diapause. The nymphs of the second generation also were reared on rape leaves; however, most of the
adults that emerged in September entered diapause (Figure 11.8). These experiments clearly showed
that although day length played the principal role in induction of winter adult diapause, the response was
modified significantly by the food in mid-summer, which thus affected the voltinism of the population.
In laboratory experiments (Figure 11.9), it was shown further that food (again, leaves and seeds of
rape) acted as a signal in this species only under long-day conditions. Under short-day conditions, all
females of Eurydema rugosa entered diapause regardless of the diet (Numata and Yamamoto 1990,
Numata 2004).
The role of the food plant in diapause induction is known for many species of phytophagous insects.
The shortage of food or a decrease in its quality usually increase the tendency to enter diapause. However,
in Eurydema rugosa the trophic conditions facilitating the onset of diapause were no less favorable than

Leaves

Seeds

Egg NymphAdult

Egg Nymph

Nymph

Adult

Leaves

E

MayJune July August September

Adult

FIGURE 11.8 Effect of diet (leaves or seeds of rape) on winter adult diapause induction in the pentatomid Eurydema
rugosa in Osaka, Japan (34.7°N) under quasi-natural conditions (nymphs and adults experienced natural day length and
temperature). Light sectors: reproductive (i.e., nondiapause) adults; black sectors: diapause adults. (From K. Ikeda-Kikue
and H. Numata, Acta Societatis Zoologicae Bohemoslovenicae 65: 197–205, 2001, with permission.)

Leaves Seeds

L:D 16:8

L:D 10:1 4

FIGURE 11.9 Effect of photoperiod and diet (leaves and seeds of rape) in winter adult diapause induction in females
of the pentatomid Eurydema rugosa in Osaka, Japan (34.7°N). Nymphs were reared to adults and then maintained under
constant experimental conditions (indicated on the left) at 25°C. Light sectors: reproductive (nondiapause) females; black
sectors: diapause females. (From H. Numata, Applied Entomology and Zoology 39: 565–573, 2004, with permission.)