NO. IO COCKROACHES—ROTH AND WILLIS IT 
control in the city’s sewers by dosing the sewage at the heads of the 
lateral sewers with orthodichlorobenzene. The first day that the treat- 
ment was applied, the influent sewage carried a mass of dead cock- 
roaches. Workmen also reported that when the dosing stations were 
put into operation, cockroaches were quickly driven out of cracks in 
the manholes. From the photograph accompanying Gary’s article 
(see pl. 2), the cockroach was apparently Periplaneta americana or 
another species of Periplaneta, 
In a recent personal communication, Dr. Theodore Olson has de- 
scribed a very heavy infestation of Periplaneta americana (pl. 3) 
which was found in the sewer system approximately 90 feet from 
the surface of the ground, under the University of Minnesota campus ; 
this sewer receives wastes from a group of hospital buildings. Dr. 
Olson wrote us as follows: “‘When I first entered the area, roaches 
scurried away in all directions and in their haste many lost their grip 
on the ceiling. As a result we were unpleasantly pelted by a shower 
of scrambling half-flying insects picked up by the gust of air which 
was produced when we opened the steel doors between the tunnel 
and the sewer. By the time we returned to take these pictures not all 
of the roaches had yet returned to the area and the photo shows only 
a part of the total aggregation. The warmth from the heating tunnel 
undoubtedly attracted the insects to this area where humidity was 
right and food and water could be obtained readily. To us it is an 
interesting example of the heavy roach population which may develop 
even in the northern tier of states.” An examination of plate 3 shows 
clearly that these insects were well established in the sewer ; nymphs, 
recently molted individuals, adult males and females, and females 
forming oodthecae are visible. 
Although most reports have implicated the American cockroach in 
sewer infestations, heavy infestations of the oriental cockroach have 
also been found in sewers in Bedford, Ind. (Anonymous, 1957) : 
“People reported roaches invading homes and apartments from out- 
lets in bathtubs, sinks and lavatories. Basements were heavily in- 
fested with ‘water bugs’ coming up through drains. Pest control 
operators were finding yards, walks and porches teeming with Oriental 
roaches at night.” Heavy cockroach infestations were found in most 
sewer manholes. Inspections two weeks and a month after the man- 
holes had been sprayed with 4-percent chlordane revealed a success- 
ful decrease in oriental cockroaches in premises. 
Lohmeyer (1953) reported an extremely heavy infestation of 
cockroaches (identified as Periplaneta americana by Dr. L. A. Hetrick 
[p. c.]) in the standard-rate trickling filter of the sewage treatment 
