NO. I0 COCKROACHES—ROTH AND WILLIS 15 
bases of buildings in the evening and were found in large numbers on 
walls and lawns. Weinman et al. (in Shuyler, 1956) stated that this 
species is frequently found outdoors around homes during the sum- 
mer months and can become exceptionally numerous in garbage and 
trash dumps. Spear et al. (im Shuyler, 1956) stated that in warm 
climates or during warm weather, the oriental cockroach may live 
outside buildings and feed inside the buildings. Shuyler (1956) re- 
ported a marked increase in the frequency of occurrence and duration 
of infestations outdoors in the temperate north-central area. He also 
stated that the yards of whole blocks of homes have been described 
as “alive” with oriental cockroaches on warm summer nights. Shuyler 
(1956) also observed that the German cockroach occurs, sometimes 
in large numbers, outside buildings. 
Experimental studies of the dispersal of marked cockroaches have 
barely scratched the surface of this field. Porter (1930) released 10 
marked Blattella germanica at Johannesburg, South Africa. Four 
were recaptured between 34 and 48 hours after release and at distances 
105 to 360 feet from the release point. The remaining 6 insects were 
not seen again. According to Stenburg (1947), the sphere of activity 
of B. germanica in houses is quite limited ; the insects seemed to move 
only short distances from their resting places and apparently always 
returned to approximately the same place. 
Schoof and Siverly (1954) released 6,500 radioactive Periplaneta 
americana in four sewer manholes in Phoenix, Ariz., in October 1952. 
Marked cockroaches were recovered at three of the release sites for 84 
weeks. One marked specimen was trapped at a yard site 60 feet from 
a release point. There was no evidence that the cockroaches migrated 
either within the sewer system or into homes. 
On the other hand, Jackson and Maier (1955), in a similar study 
in Phoenix in July 1953, obtained positive evidence of cockroach mi- 
gration from sewers. When 1,200 radioactive Periplaneta americana 
were superimposed on a native manhole population of 300, 71 tagged 
individuals were recaptured during the next 15 days. One was caught 
in a kitchen 80 feet from the manhole. Five others were caught in 
yard traps at distances of 15 to 95 feet from the release site. In 
addition, 65 tagged cockroaches were captured in the sewer system 
adjacent to the release site at distances up to 350 feet from the release 
manhole. In another experiment, 500 cockroaches native to a man- 
hole were made radioactive. Four tagged individuals were recaptured 
in 15 days of trapping, one in a yard trap 33 feet from the release 
point and three in a manhole 170 feet downstream. Similar results 
