Diapause in Pentatomoidea 511
It also should be remembered that in the field, insects experience not constant but day-to-day changing
day-length conditions: day length increases from winter until the day of summer solstice (June 20 to 22 in
the Northern Hemisphere [i.e., increasing day length]) and then decreases until winter solstice (December
20 to 23 in the Northern Hemisphere [i.e., decreasing day length]). Many insect species can sense these
small daily changes of day length and, thus, experiments with changing photoperiods often can give more
information about mechanisms controlling species’ seasonal development than experiments using constant
photoperiods (Danilevsky 1961, Saunders 1976, Tauber et al. 1986, Saulich and Volkovich 2004).
11.3.1.2 Developmental Stage(s) Sensitive to Day Length
Diapause induction which happens during the prediapause phase (see Section 11.2.1 and Figure 11.1)
involves the day-length sensitive stage and the process of accumulation of photoperiodic information.
Perception of day-length signals/cues is known to occur at a certain stage of insect development, which
is strictly species-specific and usually directly precedes the diapausing stage (Saunders 1976, Saulich
and Volkovich 2004). Sensitivity to day length in different species may appear at different stages of
development, from the egg to the adult, or extend over several stages but, again, is always strictly species-
specific. The adult diapause, typical of most pentatomoids, is characterized by the greatest variation in
which stage or stages are susceptible to day-length influence. Even in the same type of diapause, evalu-
ation of the day-length information may take place at different development stages and have a different
duration (Table 11.3; Musolin and Saulich 1999).
The duration and identity of the sensitive stage largely determine the entire pattern of seasonal devel-
opment and the adaptive capabilities of the species (Saulich 1995). This is evident especially in cases
of artificial displacement or transfer of insects into new geographic regions, which will be discussed in
detail in Chapter 12.
11.3.1.3 Required Day Number
The sensitive stage is a necessary component of the PhPR. During this stadium, the daily photoperiodic signals
are accumulated. Apparently, one short- or long-day signal is not enough to induce a response. The number of
photoperiodic cycles triggering diapause or active development has been referred to as a packet of photope-
riodic information (Goryshin and Tyshchenko 1972) or the required day number (Saunders 1976).
TABLE 11.3
Stages Sensitive to Day Length in Species of the Superfamily Pentatomoidea with Photoperiodically
Induced Winter Diapause^1
Sensitive Stages Species (References)
Nymphal Diapause
Nymphs Carbula humerigera (Kiritani 1985a,b)
Adult Diapause
Nymphs of 2nd instar Oebalus poecilus (Albuquerque 1993)
Nymphs starting from 3rd instar and adults Podisus maculiventris (Volkovich et al. 1991b)
Nymphs of last two (4th and 5th) instars, and adults or nymphs of
last (5th) instar and adults
Dolycoris baccarum (Perepelitsa 1971)
Halyomorpha halys (Niva and Takeda 2003)
Eysarcoris lewisi (Hori and Kimura 1993)
Mostly adults Graphosoma lineatum (Musolin and Maisov 1998)
Arma custos (Saulich and Volkovich 1996)
Perillus bioculatus (Jasič 1967, 1975)
Aelia acuminata (Hodek 1971a)
Chinavia hilaris (Wilde 1969)
Nezara viridula (Ali and Ewiess 1977)
Plautia stali (Kotaki and Yagi 1987)
(^1) All species belong to Pentatomidae. Examples from other families are not available.