500 Invasive Stink Bugs and Related Species (Pentatomoidea)
increase. In some cases, individuals may continue accepting food or water, building energy reserves,
and seeking suitable microhabitat during this subphase. These physiological processes are followed by
the maintenance subphase, during which the endogenous developmental arrest persists regardless of
environmental conditions. Specific token stimuli may help maintain diapause (or, in other words, prevent
its termination). During this subphase, metabolic rate is relatively low and constant. Largely unknown
physiological process(es) lead to more or less gradual decrease of diapause intensity and increase of
sensitivity to diapause-terminating environmental conditions. With time, changes in environmental
conditions can stimulate the decrease of diapause intensity to its minimum level and, thus, lead to the
termination subphase. During this subphase, the intensity of diapause further decreases. By the end of
the termination subphase, a usual active physiological state is mostly reached. Then, if conditions (pri-
marily temperature) permit, direct development may overtly resume and the insects can begin moving,
feeding, molting (in the case of nymphal/larval diapause) or copulating (in the case of adult diapause).
However, if conditions are not yet permissive (usually, temperature is still too low and/or food is not
available), the covert potentiality for direct development is restored but not realized and, as a result, the
insects do not leave the diapause microhabitat and do not become fully active.
The diapause phase is followed by the postdiapause phase. Under field conditions, the diapause phase
often ends as early as mid- or late winter or early spring, but temperature or other environmental condi-
tions do not allow active development. In this case, insects experience postdiapause quiescence, an
exogenously (i.e., externally) imposed inhibition of development and metabolism. When environmental
conditions permit, the quiescence is followed by the full resumption of active development.
Our understanding of the nature and sequence of phases of insect diapause is still incomplete. The
scheme outlined above and graphically represented in Figure 11.1 was suggested by V. Koštál (2006),
but a few other views and models have been suggested in the literature (Danilevsky 1961; Tauber et al.
1986; Danks 1987; Zaslavski 1988; Hodek 1996, 2002; Saulich and Volkovich 2004; Belozerov 2009).
Below, we shall consider these sequential phases of diapause, using pentatomoids as examples.
11.2.2 Three Types of Diapause in Pentatomoidea:
Embryonic (Egg), Nymphal, and Adult Diapause
Diapause in different insect species can be confined to any developmental stadium from embryo to adult.
In the Heteroptera, three types of diapause are recognized including embryonic (or egg), nymphal, and
PrediapausePostdiapause
QuiescenceStart End
ResumptionMaintenanceEndogenous Exogenous
Direct developmentDevelopmental arrest Direct developmentPreparationInduction Initiation TerminationDiapauseFIGURE 11.1 Schematic depiction of sequential phases of insect diapause. Thick line with arrowhead in the lower part
of the figure indicates the passage of life of a hypothetical insect individual. Three major phases, namely prediapause, dia-
pause, and postdiapause are named (on the top). Prediapause can be divided into the induction and preparation subphases
and diapause into the initiation, maintenance, and termination subphases; postdiapause can be represented by quiescence.
Developmental arrest may be endogenously (i.e., internally) or exogenously (i.e., externally) controlled (see at the bottom
of the figure). More details are given in Section 11.2.1. Note that not all the (sub)phases must necessarily be found in all
species and situations and this depiction might be applied to any type of diapause (i.e., embryonic, nymphal or adult; see
Section 11.2.2 for details). (Modified from V. Koštál, Journal of Insect Physiology 52: 113–127, 2006, with permission.)