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

Fig. 3.12 Average monthly numbers of cockroaches in light
traps at 1, 17, and 35 m in height during three trapping periods;
flowering status of the trees varied during these periods.
The study was conducted in tropical lowland dipterocarp forest
in Sarawak, Malaysia. After Itioka et al. (2003), with permission
of T. Itioka.
and adventitious roots. These provide sheltered resting
places and a substantial amount and variety of food, particularly
in the form of suspended soils. Fisk (1983) found
a general albeit inconsistent correlation between number
of cockroaches collected during fogging and the number
of lianas per tree. Floren and Linsenmair (1997) fogged
trees from which all lianas and epiphytes were removed in
Sabah, and found that cockroaches did not exceed 1% of
the insects collected, on average. The substantial pool of
suspended soil that accumulates in the various nooks and
crannies of the canopy may be particularly important in
understanding the vertical stratification of cockroach
faunas (Young, 1983), yet it is commonly neglected in
tropical canopy research (Winchester and Behan-Pelletier,
2003). Suspended soil has a high organic content derived
from leaf, fruit and flower litter, epiphyte tissues, decomposing
bark, and the feces, food, and faunal remains
of canopy-dwelling animals. It also contains a mineral
component derived from fine particles carried on wind,
rain, and fog (Winchester and Behan-Pelletier, 2003).
This above-ground humus in rainforest is often thicker
than the rapidly decomposing layer on the ground, and
cockroaches that utilize the plant litter on the forest floor
may also do so in the litter of the canopy. Leaf litter in
plastic cups suspended in the lower branches of cacao
trees in Costa Rica attracted cockroaches. Most abundant
were species of Latiblattella and Eurycotis; the latter was
also found in ground litter (Young, 1983). Studies of
arthropods to date, however, generally indicate that the
soil/litter fauna on the forest floor is in large measure distinct
from that of the forest above (Basset et al., 2003b).
One example among cockroaches is Tho. porcellana,
which lives in aerial litter caught by the interlaced horizontal
branches of plants in scrub jungle in India. The entire
lifecycle of this cockroach is confined to suspended
soil; they have no direct contact with the substratum
(Bhoopathy, 1997).Winchester and Behan-Pelletier (2003)
found that unidentified cockroaches collected from suspended
soil cores from the crown of an Ongokea gore tree
in Gabon were stratified; they were more abundant at 42
m than at 32 m above the ground.
Canopy litter is often considered ephemeral, as it can
be removed by disturbances such as wind, rain, and arboreal
animals (Coxson and Nadkarni, 1995). That is not
true of the suspended soil trapped in some of the container
epiphytes, such as the bird’s nest Asplenium ferns
and species of Platycerium with basal, clasping structures.
In both, the litter mass acts as a sponge to retain water and
nutrients (Rundel and Gibson, 1996). In the Neotropics
epiphytes and hemiepiphytes may comprise greater than
60% of all individual plants, individual trees may support
several hundred bromeliads, and a single bromeliad can
contain more than 100 gm of soil (Gentry and Dodson,
1987; Paoletti et al., 1991). This is a substantial resource
pool for cockroaches that feed on the accumulated debris
and microorganisms contained within. Dejean and Olmsted
(1997) found cockroaches in 67–88% of collected
bromeliads (Aechmea bracteata) examined on the Yucatan
peninsula of Mexico. Rocha e Silva Albuquerque et
al. (1976) identified more than 30 cockroach species in
bromeliads and list additional ones from the literature.
60 COCKROACHES