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

these has a social component, in that each can be based
on interactions with conspecifics rather than the external
environment.
Injury and Development
There is a large body of literature indicating that minor
wounds in cockroach juveniles delay development. Injuries
to legs, cerci, and antennae result in an increased
number of instars, in the prolonged duration of an instar,
or both (Zabinski, 1936; Stock and O’Farrell, 1954; Willis
et al., 1958; Tanaka et al., 1987). The developmental delay
may be attributed to the allocation of limited resources,
because energy and nutrients directed into wound repair
and somatic regeneration are unavailable for progressive
development (Kirkwood, 1981). This relationship between
injury and development may be relevant to termites
in two contexts. First, in a variety of lower termites,
mutilation of the wing pads and occasionally other body
parts is common (e.g., Myles, 1986). These injuries are
hypothesized to result from the bites of nest mates, and
they determine which individuals fly from the nest and
which remain to contribute to colony labor. Injured individuals
do not proceed to the alate stage, but instead undergo
regressive or stationary molts (Roisin, 1994). The
aggressive interactions that result in these injuries may be
the expression of sibling manipulation if larvae, nymphs,
or other colony members are doing the biting (Zimmerman,
1983; Myles, 1986), or they could indicate fighting
among nymphs that are competing for alate status
(Roisin, 1994).
A second, peculiar, termite behavior also may be linked
to the physiological consequences of injury. After a
dealate termite pair becomes established in its new nest,
the male and female typically chew off several terminal
segments of their own antennae, and/or those of their
partner (e.g., Archotermopsis—Imms, 1919; Cubitermes
—Williams, 1959; Porotermes—Mensa-Bonsu, 1976;
Zootermopsis—Heath, 1903). This behavior is also
recorded in several cockroach taxa. Nymphs of B. germanica
self-prune their antennae (autotilly)—the ends
are nipped off just prior to molting (Campbell and Ross,
1979). Although first and second instars of Cryptocercus
punctulatus almost always have intact antennae, cropped
antennae can be found in third instars and are common
in fourth instars (Nalepa, 1990). Nymphs and adults of
the myrmecophiles Att. fungicola and Att. bergi usually
have mutilated antennae (Bolívar, 1901; Brossut, 1976),
but Wheeler (1900) was of the opinion that it was the host
ants that trimmed them for their guests. He likened it to
the human habit of cropping the ears and tails of dogs.
The developmental and/or behavioral consequences of
antennal cropping are unknown for both termites and
cockroaches.
Nutrition and Development
Cockroach development is closely attuned to nutritional
status (Gordon, 1959; Mullins and Cochran, 1987). Poor
food quality or deficient quantity results in a prolongation
of juvenile development via additional molts and/or
prolonged intermolts (Hafez and Afifi, 1956; Kunkel,
1966; Hintze-Podufal and Nierling, 1986; Cooper and
Schal, 1992). Diets relatively high in protein produce the
most rapid growth (Melampy and Maynard, 1937), and
on diets lacking protein, nymphs survive for up to 8 mon,
but eventually die without growing (Zabinski, 1929). The
effect of nutrition on development is most apparent in
early instars, corresponding to what is normally their period
of maximum growth (Woodruff, 1938; Seamans and
Woodruff, 1939). A nutrient deficiency in a juvenile cockroach
results in a growth stasis, in which a semi-starved
nymph “idles”until a more adequate diet is available. This
plasticity in response to the nutritional environment is
suggestive of the arrested development exhibited by
workers (pseudergates) in lower termite colonies, and is
hypothesized to be one of the key physiological responses
underpinning the shift from subsocial to eusocial status
in the termite lineage (Nalepa, 1994, discussed below).
Reproductive development is also closely regulated by
the availability of food in cockroaches. Females stop or
slow down reproduction until nutrients, particularly the
amount and quality of ingested protein, is adequate
(Weaver and Pratt, 1981; Durbin and Cochran, 1985;
Pipa, 1985; Mullins and Cochran, 1987; Hamilton and
Schal, 1988). In P. americana the initial response to lack
of food is simply the slowing down of oocyte growth, but
if starvation becomes chronic the corpora allata are
turned off and reproduction effectively ceases. When
food once again becomes available the endocrine system
is rapidly reactivated and normal reproductive activity
follows within a short time (Bell and Bohm, 1975).
Kunkel (1966, 1975) used feeding as an extrinsically controllable
cue for synchronizing both the molting of
nymphs and the oviposition of females in B. germanica
and P. americana. There is substantial evidence, then, that
domestic cockroaches tightly modulate “high demand”
metabolic processes such as reproduction and development
in response to changes in food intake, and that both
physiological processes can be controlled in individuals
by manipulating their food source.
Group Effects and Development
Group effects (discussed in Chapter 8) can have a profound
effect on the developmental trajectory of juvenile
cockroaches and are known from at least three families of
Blattaria (Table 8.3). Nymphs deprived of social contact
typically have longer developmental periods, resulting
156 COCKROACHES