16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
were reported earlier by these workers (Jackson and Maier, 1953, 
1954). 
Eads et al. (1954) observed the dispersal of marked Periplaneta 
americana from sewers in Tyler, Tex. Prior to the experiment, they 
had observed as many as 11 cockroaches per hour leave a manhole 
at night (pl. 5). In May 1953, 1,000 cockroaches were painted and 
returned to the manhole from which they were originally obtained. 
The first recovery of a marked cockroach was from an apartment 
house 6 days after the release. Within a 3-week period, 15 marked 
cockroaches were recovered from the same apartment house. So 
many other marked cockroaches were seen by the residents that they 
demanded that the manhole be sprayed to eliminate the insects. About 
2 months after the release, one marked cockroach was taken in a gro- 
cery one block from the release site. After a second release of I,000 
marked cockroaches in another manhole, 5 were collected in a home 
adjacent to the release site. Four marked specimens were killed in a 
home 3 days after a third release of 1,000 painted cockroaches. A 
week after a fourth release, one marked insect was captured in a home. 
It has been conclusively demonstrated that cockroaches do migrate 
from sewers into homes. Probably the extent of migration is much 
greater than recovery of marked insects would indicate. The mark- 
ing technique is admittedly an insensitive method for measuring insect 
dispersal because so few marked insects are ever recovered. The 
problem is further complicated by the probable migration of unmarked 
cockroaches from the sewers between manholes. In the cited experi- 
ments, large numbers of unmarked cockroaches were trapped with 
the few marked individuals. If a means could be devised for marking 
all cockroaches within a sewer system, the extent of migration into 
adjacent dwellings would undoubtedly be much more readily apparent. 
III. VIRUSES 
Recent laboratory studies have shown conclusively that cockroaches 
may acquire, maintain, and excrete various viruses. Results of these 
experiments are described in Appendix A. Four unspecified strains 
of poliomyelitis virus have been found occurring naturally in wild- 
caught cockroaches. Four identified strains of poliomyelitis virus 
have been successfully inoculated into cockroaches with subsequent 
recovery of virus. In addition, cockroaches have also been experi- 
mentally infected with Coxsackie virus, mouse encephalomyelitis 
virus, and yellow-fever virus. 
Natural transmission of viral diseases by cockroaches has not yet 
been proved, but the published data show that cockroaches are cer- 
