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

FIVE
Microbes:
The Unseen Influence
on the
back of a cockroach
no larger than
myself millions of
influenza germs may lodge i
have a sense of responsibility
to the public and i
have been lying for two weeks
in a barrel of moth
balls in a drug store
without food or water
—archy, “quarantined”
Why are cockroaches almost universally loathed? One of the primary reasons is because
of the habitats they frequent in the human environment. Cockroaches are associated with
sewers, cesspools, latrines, septic tanks, garbage cans, chicken houses, animal cages, and
anywhere else there are biological waste products. Their attraction to human and animal
feces, rotting food, secretions from corpses, sputum, pus, and the like gives them a well
earned “disgust factor” among the general public (Roth and Willis, 1957). Why, however,
are they are attracted to environments reviled by most other animals? It is it is obvious
to us that the common denominator in all these moist, organic habitats is the staggeringly
dominant presence of bacteria, protozoa, amoebae, fungi, and other microbial material.While
these consortia are rarely if ever discussed as food for macroarthropods (e.g.,
Coll and Guershon 2002), in the case of cockroaches, that may be a glaring oversight. The
main source of nourishment for cockroaches in mines and sewers, for example, is human
feces (see Roth and Willis, 1957, plate 4), which can be 80% bacterial, by fresh weight
(Draser and Barrow, 1985). Blattella germanica has been observed feeding on mouth secretions
of corpses riddled with lung disease; these secretions contained infectious bacteria
in almost pure culture (Roth and Willis, 1957). Granted, the above cases refer to
cockroaches associated with the man-made environment, while the main focus of this
book is on the 99% species that live in the wild. We contend, however, that microbes
are an essential influence in the nutrition, ecology, and evolution of all cockroaches; indeed,
it can be difficult to determine the organismal boundaries between them. Here we
address microbes as gut and fat body mutualists, as part of the external rumen, the food
value of microbes, various mechanisms by which cockroaches may ingest them, and
some non-nutritional microbial influences. Finally, we discuss some strategies used by
cockroaches to evade and manage disease in their microbe-saturated habitats.
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