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

from both decreased weight gain per stadium and increased
stadium length (Griffiths and Tauber, 1942b;
Willis et al., 1958; Wharton et al., 1968; Izutsu et al., 1970;
Woodhead and Paulson, 1983). In P. americana, nymphs
isolated at day 0 are one-half to one-third the size of
grouped nymphs after 40 days (Wharton et al., 1968). The
effect is cumulative, with no critical period. It occurs at
any stage of development and is reversible at any stage
(Wharton et al., 1967; Izutsu et al., 1970). Respiration of
isolates may increase, and new proteins, expressed as
electrophoretic bands, may appear in the hemolymph
(Brossut, 1975; pers. comm. to CAN). The physiological
consequences seem to be caused by a lack of physical contact
(Pettit, 1940; Izutsu et al., 1970) and the presence of
even one other individual can ameliorate the effects
(Izutsu et al., 1970; Woodhead and Paulson, 1983). The
means by which tactile stimuli orchestrate the physiological
changes characteristic of the group effect in cockroaches
is unknown. In termites, as in cockroaches, the
physical proximity of conspecifics significantly increases
the longevity and vigor of individuals, with just one nestmate
as sufficient stimulus. This “reciprocal sensory intimacy”
is thought to play a key, if unspecified, role in caste
determination (Grassé, 1946; Grassé and Noirot, 1960).
Heterochrony: Evolutionary Shifts
in Development
Termites are essentially the Peter Pans of the insect
world—many individuals never grow up. Most colony
members are juveniles whose progressive development
has been suspended. Even mature adult termites exhibit
numerous juvenile traits when compared to adult cockroaches,
the phylogenetically appropriate reference group
(Nalepa and Bandi, 2000). Termites therefore may be described
as paedomorphic, a term denoting descendent
species that resemble earlier ontogenetic stages of ancestral
species (Reilly, 1994). The physical resemblance of
termites and young cockroaches is indisputable, and is
most obvious in the bodily proportions, the thin cuticle,
and a short pronotum that leaves the head exposed.
Cleveland et al. (1934) and Huber (1976) both noted the
resemblance of early instars of Cryptocercus to larger termite
species, with the major difference being the more
rapid movement and longer antennae of Cryptocercus
(Fig. 9.5). One advantage that termites gain by remaining
suspended in this thin-skinned morphological state is the
avoidance of a heavy nitrogenous (Table 4.5) investment
in cuticle typical of older developmental stages of their
cockroach relatives.
Cockroaches that are paedomorphic display a variety
of termite-like characters such as thinning of the cuticle,
eye reduction, and decrease in the size of the pronotal
Fig. 9.5 First instar of Cryptocercus punctulatus. Photo by C.A.
Nalepa.
shield (e.g., Nocticola australiensis—Roth, 1988). These
cockroaches are often wingless, but when wings are retained
they can resemble those of termite alates. In Nocticola
babindaensis and the genus Alluaudellina ( Alluaudella),
the forewings and hindwings are nearly the same
length, they considerably exceed the tip of the abdomen,
both sets are membranous, and they have a reduced venation
and anal lobe (Shelford, 1910a; Roth, 1988).
The expression of altered developmental timing in termites
is not limited to morphological characters. It includes
aspects of both behavior and physiology that are
more characteristic of the juvenile rather than the adult
stages of their non-eusocial relatives. Just as maturation
of the body became truncated during paedomorphic evolution
in the termite lineage, so did many features of behavioral
and physiological development. Elsewhere in
this chapter we noted several behaviors that are common
to termites and cockroach taxa, including burrowing,
building, substrate manipulation, trail following, and vibrational
alarm behavior. There are additional behaviors
crucial to termite social cohesion shared only with the
early developmental stages of cockroaches (Nalepa and
Bandi, 2000). In most cockroach species, young nymphs
have the strongest grouping tendencies, and in some,
early instars are the only stages that aggregate (Chapter
8). Early cockroach instars often display the most pronounced
kin recognition (Evans and Breed, 1984), the
most intense cannibalism (Wharton et al., 1967; Roth,
1981a), and the most frequent coprophagy (Nalepa and
Bandi, 2000).Young Periplaneta nymphs affix fecal pellets
to the substrate more often than do older stages (Deleporte,
1988). Antennal cropping is displayed in nymphs
of two cockroach species, and it is only young developmental
stages of Cryptocercus that allogroom (Seelinger
and Seelinger, 1983). All of these behaviors are standard
elements of the termite behavioral repertoire.
TERMITES AS SOCIAL COCKROACHES 157