Diapause in Pentatomoidea 527
as a trigger for spring reproduction was demonstrated in experiments with the pentatomid Dybowskyia
reticulata (Nakamura and Numata 1997a). The females collected in the field and transferred into the
laboratory in March started to lay eggs under both long-day and short-day conditions, but only in the
presence of food (Figure 11.15).
In the absence of food, oviposition was delayed by a considerable period under both long- and short-
day conditions. Availability of food stimulated reproduction (the moment of the appearance of food is
marked with an arrow in Figure 11.15). Thus, the onset of reproduction in this species in spring is not
controlled by either temperature or day length but is determined solely by the availability of food. In
summer, the presence of food and its quality usually act as secondary cues whereas in spring, the absence
of food becomes the main factor hindering gonad maturation.
11.7 Seasonal Adaptations Associated with Winter Diapause
In addition to winter diapause, pentatomoids have a diverse set of seasonal adaptations that allow them
to synchronize their growth and reproduction with the seasons optimal for such activities and dormancy
periods with the harsh periods of the year.
11.7.1 Migrations to and from Overwintering Sites
Migration is a complex phenomenon widely spread throughout the Heteroptera, including the
Pentatomoidea. It is difficult to define insect migration but Dingle (1996, p. 38) listed five characteristics
that distinguish migration from other forms of movements. These are: (1) it is persistent; (2) it is straight-
ened out; (3) it is undistracted by resources that would ordinarily halt it; (4) there are distinct departing
and arriving behaviors; and (5) energy is reallocated to sustain it. Dingle (1996) also stressed that not all
migrants display all of these characteristics all of the time, but most will display most of them at least
part of the time during which they are migrating. Migrations often happen seasonally and differ from
sporadic and short-distance dispersal and other forms of movements in space aimed at search for habi-
tats for feeding, oviposition, etc. Distances covered by migrating true bugs might differ manyfold, from
hundreds of meters to hundreds of kilometers (Saulich and Musolin 2007a,b).
100500100500
01530
0
015304560
Days DaysL:D 12:12 L:D 12:12Survival andpercentage of ovipositioning females, %L:D 16:8 L:D 16:8FIGURE 11.15 Survival and oviposition of females of the pentatomid Dybowskyia reticulata from Osaka, Japan (34.7°N)
transferred in late March from the field to the laboratory short-day (L:D 12:12) and long-day (L:D 16:8) conditions at 25°C.
Light areas: nonovipositing females; shaded areas: females that started laying eggs. Arrows mark the moment when food
became available. (From H. Numata, Applied Entomology and Zoology 39: 565–573, 2004, with permission.)