NO. IO COCKROACHES—ROTH AND WILLIS 13 
Of 67 sewer manholes examined in Austin, Tex., over 77 percent 
contained light to heavy infestations of Periplaneta americana (Eads 
et al., 1954). In Galveston, Houston, and Corpus Christi, Tex., Eads 
et al. (1954) found the American cockroach present in over 50 per- 
cent of the manholes inspected. They reported that similar conditions 
were found in other Texas cities. 
Domestic cockroaches may live and breed in close association with 
their food, or they may move out of sheltered areas under cover of 
darkness and migrate to obtain food and water. Natural migrations 
of cockroaches have been observed only a few times. Probably migra- 
tions are common, but as they undoubtedly occur at night or other 
periods of low illumination, they have seldom been observed. Recent 
experimental studies, reported below, have been made in an attempt 
to determine the extent of cockroach dispersal from sewers. This 
field holds much promise and it is hoped that further studies will be 
made. 
Dorsett (in Howard, 1895), on a dark, drizzly day, observed thou- 
sands of Blattella germanica issue from the rear of an old restaurant 
in Washington, D. C., and march directly across a muddy street to 
the building opposite. Several men with brooms were unable to stop 
the advance. Howard believed that this was a true migration brought 
about by overpopulation, as there was no evidence of insecticide being 
used in the restaurant. 
Walden (1922) reported a heavy infestation of Blattella germanica 
in a dump in New Haven, Conn. At one edge of the dump this species 
was found in numbers under loose bark and in cavities in trees. Sev- 
eral specimens of Periplaneta americana were also found in the trees. 
The cockroaches were active at night and swarmed on nearby houses 
and street trees as far as a city block from the dump. Felt (1926, 
1928) reported a similar occurrence in a city in the Hudson Valley, 
in which B. germanica multiplied in a dump to such an extent that it 
became a veritable nuisance to the neighborhood. Hansens (1949, 
1950) stated that a dump in New Jersey was sprayed with fuel oil 
and set on fire in an attempt to control German cockroaches: “This 
treatment resulted in flights up to four blocks from the dump even 
though these insects do not usually fly. There are a number of other 
instances where fire has resulted in otherwise harmless and unnoticed 
cricket and roach infestations becoming municipal problems in a few 
hours.” Many years ago in Austin, Minn., Dr. Theodore Olson (p. c.) 
witnessed a mass migration of B. germanica from a city dump to a 
relatively new sewage treatment plant approximately one-quarter of a 
mile away. “The insects completely overran the plant even penetrating 
