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

doubt that the evolution of eusociality was the event that
rocketed the termite lineage into a new adaptive zone. A
correlate of universal and complex social behavior among
extant termites, however, is the difficulty in developing
models of ancestral stages based on characters of living
Isoptera. Because the best-supported phylogenetic hypotheses
have termites nested within the Blattaria, we
have license to turn to extant cockroaches, and in particular
to Cryptocercus, in our search for a phylogenetic
framework within which termite eusociality, and thus the
lineage, evolved. It is a big topic, and one that can be explored
from several points of view. Here we take a broad
approach.We first examine how a variety of behaviors key
to termite sociality and colony integration have their
roots in behaviors displayed by living cockroach species.
We then focus on cockroach development, its control,
and how it can supply the raw material for the extraordinary
developmental plasticity currently exhibited by the
Isoptera. We address evolutionary shifts in developmental
timing (heterochrony), and how these played crucial
roles in the genesis and evolution of the termite lineage
from Blattarian ancestors. We then turn to proximate
causes of termite eusociality, first discussing how a wood
diet and the symbionts involved in its digestion and assimilation
provide a framework for the social transition.
Finally, using young colonies of Cryptocercus as a model
of the ancestral state, we show how a simple behavioral
change, the assumption of brood care duties by the oldest
offspring in the family, can account for all of the initial,
defining characteristics of eusociality in termites.
THE BEHAVIORAL CONTINUUM
Fig. 9.2 Similarity of feeding behavior in a cockroach and a
mantid. (A) Supella longipalpa standing on four legs while
grasping a food item with its spined forelegs. (B) Unidentified
mantid feeding on a caterpillar, Zaire. Both photos courtesy of
Edward S. Ross.
Striking ethological similarities in cockroaches and
termites have been recognized since the early 1900s
(Wheeler, 1904). These behavioral patterns probably
arose in the stem group that gave rise to both taxa (Rau,
1941; Cornwell, 1968) and may therefore serve as points
of departure when hypothesizing a behavioral profile of
a termite ancestor. The most frequently cited behaviors
shared by cockroaches and termites are those that regulate
response to the physical environment. Both taxa are,
in general, strongly thigmotactic (Fig. 3.7), adverse to
light, and associated with warm temperatures and high
humidity (Wheeler, 1904; Pettit, 1940; Ledoux, 1945).
Additional shared behaviors include the use of conspecifics
as food sources (Tables 4.6 and 8.4), the ability
to transport food (Chapter 4), aggregation behavior,
elaborate brood care (Chapter 8), hygienic behavior, allogrooming
(Chapter 5), and antennal cropping, discussed
below. The remaining behaviors common to Blattaria
and Isoptera fall into one of two broad domains that
we address in the following sections: those related to
communication (vibrational alarm behavior, trail following,
kin recognition) and those associated with nesting
and building behavior (burrowing, substrate manipulation,
behavior during excretion).
Communication: The Basis
of Integrated Behavior
Complex communication is a hallmark of all social insects
(Wilson, 1971). Most termites and cockroaches,
however, differ from mantids and the majority of Hymenoptera
in conducting all day-to-day activities, including
foraging, in the dark. Both Blattaria and Isoptera
rely heavily on non-visual mechanisms to orient to resources,
to guide locomotion, and to communicate.
Vibrational Communication
Termites use vibratory signals in several functional contexts.
Drywood termites, for example, assess the size of
wood pieces by using the resonant frequency of the substrate
(Evans et al., 2005). When alarmed, many termite
species exhibit vertical (head banging) or horizontal
oscillatory movements that catalyze increased activity
throughout the colony (Howse, 1965; Stuart, 1969).
152 COCKROACHES