Cockroache; Ecology, behavior & history - W.J. Bell

latter two species diapause in winter in alternate years,
but there is complex intrapopulation variability in both
species. At the onset of winter the nymphs move to grass
tussocks and assume a characteristic posture: the body is
flexed ventrally and the legs and antennae are held close
to the body. Nymphs may feed during the winter, but no
molting occurs from the end of September until the end
of April or beginning of May. Adults are short lived; males
die shortly after mating in June, but females live until October
(Brown, 1973a, 1973b, 1980, 1983). It is also notable
that of the three species of Ectobius in Great Britain, the
smallest species, E. panzeri (Brown, 1952), is the only one
with a univoltine cycle. Ectobius duskei, abundant in the
bunch grasses of Asian steppe zones, is also univoltine
and endures winters of 30 to 40C in the egg stage
(Bei-Bienko, 1950, 1969). It is thought that short favorable
seasons often lead to compressed life histories such
as these, characterized by brief developmental times, high
growth rates, and smaller adult sizes (Abrams et al.,
1996). A radically different life history, however, is exhibited
by temperate cockroaches in the genus Cryptocercus,
and by members of the blaberid subfamily Panesthiinae.
Nymphs have extended developmental periods and the
full length of the growing season is required to complete
a reproductive episode in both Cryptocercus and Panesthia
(Rugg and Rose, 1984b). Female C. punctulatus
paired with males the previous summer begin exhibiting
ovariole and accessory gland activity in April and oviposit
in late June and early July. Oothecae hatch in late July and
early August, with most neonates reaching the third or
fourth instar prior to the onset of winter (Nalepa, 1988a,
and pers. obs.). Additional temperate species that have
been studied include An. tamerlana in the Turkmenistan
desert (3-yr lifecycle in males, 4–6 yr in females) (Kaplin,
1995), and P. japonica, with a 2-yr lifecycle. The first winter
is passed as early instar nymphs, the second one as
late-instar nymphs (Shindo and Masaki, 1995).
Recently Tanaka and Zhu have been studying the lifecycles
of several species of subtropical cockroaches on
Hachijo Island in Japan. Margattea satsumana is a univoltine
species that overwinters as a non-diapause
adult. Nymphs undergo a summer diapause, but develop
quickly in autumn under short-day photoperiods. The
authors suggest that the summer diapause of nymphs is
related to a need for timing reproduction during the following
spring (Zhu and Tanaka, 2004b). Opisthoplatia
orientalis and Symploce japanica on this island are both
semi-voltine. The latter has a complex 2-yr lifecycle with
three kinds of diapause (Tanaka and Zhu, 2003): a winter
diapause in mid-size nymphs, a summer diapause in latestage
nymphs, and a winter diapause in adults. Opisthoplatia
orientalis is a large (25–40 mm) brachypterous
species capable of overwintering successfully in any stage
Fig. 3.6 Lifecycle of three species of Ectobius in Great Britain.
After Brown (1973b), with permission from V.K. Brown.
without diapause. The ovoviviparous females spend the
winter with several different stages of oocytes and embryos
held internally, but the growth of these is suppressed.
Most of the eggs and embryos do not survive to
partition. As a result female ovarian development is reset
in spring; there is a synchronized deposition of nymphs
in summer, most of which reach the fifth instar prior to
winter (Zhu and Tanaka, 2004a). This somewhat odd
strategy may be related to the fact that these cockroaches
are at the northern limit of their distribution on Hachijo
Island, where they are not endemic.
RANGE OF HABITATS
Cockroaches are found in a continuum of dark, humid,
poorly ventilated, and often cramped spaces either continuously
or when sheltering during their non-active period.
Although certain species may be associated with a
particular crevice type like the voids beneath rocks or the
space beneath loose bark, others are commonly found in
more than one of these habitat subdivisions. Many species
exploit the interconnectivity of dark, enclosed spaces
wherever there is suitable food and moisture, and a distinctive
classification of cockroaches as either obligate or
facultative inhabitants of caves, litter, or soils is not always
a natural one (Peck, 1990). The cave and the forest floor
differ far more from the open-air habitat than they do
from each other (Darlington, 1970). In closely grown
tropical and subtropical forest almost all atmospheric
movements are inhibited, surface evaporation of the
leaves maintains a high humidity, and the canopy shields
the forest floor from the direct rays of the sun. Cockroaches
that live in the maze of hiding places that exist in
suspended soils or on the forest floor live in a doubly
blanketed environment, as moist plant litter further
dampens the small fluctuations of light, temperature, and
humidity that prevail throughout the forest (Lawrence,
1953). Caves, on the other hand, encompass a continuum
of various sized dark, humid voids. To an arthropod,
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