58 Trans. Acad. Scr. of St. Louts 
The oriental roaches are nocturnal in habit, remaining 
within their dark abodes during the day, sallying forth 
under cover of darkness to seek their food, and, being 
fleet of foot, scurrying with astonishing speed to a place 
of safety in the event of danger. They leave in their 
runways the persistent ‘‘roachy’’ odor, which, according 
to Marlatt, comes partly from their excrement, but 
chiefly from the dark-colored fluid exuded from their 
mouths. 
Cockroaches appeared very early in geologic time, 
some representatives appearing as early as the middle 
Silurian and many in the Carboniferous age. In all, 
about 130 species have been described from the 
Palaeozoic rocks of the United States. For millions of 
years the roaches have remained stable. This must be 
due to one of two causes: either the environmental con- 
ditions have remained constant, or the insect persisted 
immutable despite changed conditions. Undoubtedly the 
conditions have changed since the species took to feed- 
ing from man’s larder, but since the insects are 
omnivorous, these changes may have been one of degree 
and not of kind. The roach has probably reached that 
stage of perfection where the habits are standardized. 
Variation is curtailed, because there is nothing to be 
gained by it; if variants should occur, they would soon 
be eliminated. The roach has survived through untold 
generations, whereas other species have suffered altera- 
tion or extermination. Moreover, there is no great differ- 
ence between the present and the fossil forms in so far as 
their morphology is concerned. Early in the phylogeny 
of the race, they became omnivorous, probably distaste- 
ful to other creatures, fleet of foot, and fecund. That 
these adaptations were eminently successful is evidenced 
