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

The first and most obvious requirement is for basic information
on the diversity, abundance, and biology of
free-living species, as cockroaches remain a largely uninvestigated
taxon. In 1960, Roth and Willis indicated that
there were 3500 described species and estimated an additional
4000 unnamed species. Currently, most estimates
are in the range of 4000 to 5000 living cockroaches, with
at least that many yet to be described. Some of the most
diverse families, such as Blattellidae, are strongly represented
in tropical climes but very poorly studied (Rentz,
1996). Among described species, the observation by Hanitsch
(1928) that “the life history of the insect begins in
the net and ends in the bottle” still holds true for the vast
majority. Core data on cockroach biology are derived
nearly exclusively from insects that have been reared in
culture and studied in the laboratory. How closely the results
of these studies relate to Blattaria in natural habitats
is in many cases questionable. Laboratory-reared cockroaches
are domesticated animals typically kept in mixed
sex, multiage groups within restricted, protected enclosures,
and supplied with a steady, monotonous food
source, ad lib water, and readily accessible mating partners.
Most tropical species cultured in the United States
are derived from just a few sources collected decades ago
(LMR, pers. obs.), and are therefore apt to be lacking the
variation expressed in free-living populations. The group
dynamics (Chapter 8), locomotor ability (Akers and Robinson,
1983; Chapter 2), and fecundity (Wright, 1968) of
laboratory cockroaches are known to differ from that of
wild strains, and crowded rearing conditions and the inability
to emigrate can result in artificially elevated levels
of density-dependent behaviors such as aggression and
cannibalism. Mira and Raubenheimer (2002) compared
laboratory-reared P. americana to “feral” animals loose in
their laboratory building and found that the free-range
cockroaches had higher growth rates, additional nymphal
stadia, greater resistance to starvation, and a higher
numbers of endosymbiotic bacteria in the fat body. Field
studies and experiments that incorporate a realistic simulation
of field conditions are clearly desirable, incorporating
as wide a range of taxa and habitat types as possible.
A small army of eager young nocturnal scientists, and
perhaps octogenarians, who cannot sleep anyway (LMR,
pers. obs.), need to consider cockroaches as worthy subjects
of observation and experimentation under natural
conditions.
A second requisite for progress lies in bankrolling the
training of a new generation of cockroach systematists, a
need made especially acute with the passing of the second
author of this volume (CAN, pers. obs.). Field studies will
have little value if the subject of research efforts cannot be
identified, or if collected vouchers languish undescribed
in museum drawers. One of LMR’s final publications
sounded the call for “true systematists interested in studying
the biology and classification of cockroaches,”but recommended
that “he or she marry a wealthy partner”
(Roth 2003c).
Even if these two requirements are in some small measure
met, progress in evaluating the ecological impact of
cockroaches may be hindered unless we recognize the
need for some attitudinal shifts in our approach to cockroach
studies. First, evaluation of the role of cockroaches
in the nutrient cycles of ecosystems demands a microbially
informed perspective (Chapter 5). Relationships
with microorganisms as food, on food, transient through
the digestive tract, and resident in and on the body not
only form the functional basis of cockroach performance
on a plant litter diet, but also direct their impact on decompositional
processes. Second, it might behoove us to
keep the phylogenetic and ecological relationships of
cockroaches and termites in mind when attempting to assess
the role of Blattaria in ecosystems. Sampling and
evaluation techniques employed in termite studies (e.g.,
Bignell and Eggleton, 2000) may also prove useful in
studying their cryptic cockroach relatives. Scattered hints
in the literature that the two taxa may be ecologically displacing
each other in selected habitats would be well
worth characterizing and quantifying. Third, and finally,
as biologists we have a responsibility to help alter the
lenses through which potential students as well as the
general public characteristically regard the subjects of this
book. A realistic image with which to begin public relations
is that of inconspicuous workhorses, acting beneath
the radar to move nutrients through the food web, maintain
soil fertility, and support a variety of the complex and
cascading processes that sustain healthy ecosystems.
ECOLOGICAL IMPACT 175