42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
rat nematode Gongylonema neoplasticum which they thought was in 
some way related to cancer in rats (see p. 27). Cordier (1933) 
suggested that Entamoeba blattae, an amoeba found in the intestines 
of cockroaches, was a causal agent of cancer. 
Kala azar.—Before the vector of this leishmaniasis was believed to 
be the sand fly, cockroaches were suspected of being possible vectors 
(Young, 1924). Examinations of dissected cockroaches, including 
Blatta orientalis, taken in endemic areas in the Sudan (Archibald, 
1923) and in southern India (Turkhud et al., 1926) were negative 
for the parasites. 
Malaria.—Coronado (in Cao, 1898) stated without evidence in an 
1897 paper that cockroaches, among other insects, spread this mos- 
quito-borne disease. 
Pellagra—Jennings and King (1913) reported negative results in 
an attempt to incriminate cockroaches in the cause and spread of this 
deficiency disease. 
Scurvy.—Melville-Davison (1911) attributed this deficiency disease 
to a gregarine found in the intestines of the cockroach. The symptoms 
of the disease, he thought, were caused by a toxin generated by the 
protozoan. 
XIV. COCKROACHES VERSUS HOUSE FLIES 
“The common housefly, loaded with all kinds of bacteria, benign 
and pathogenic, . . . offers no more danger from acute infectious 
diseases than does the common house roach. . .” (Longfellow, 1913). 
These words are as true today as they were when written. However, 
the domestic cockroaches have yet to achieve generally the unenviable 
reputation of the filth flies as carriers of infectious agents, in spite of 
this quotation from a recent U. S. Public Health Service publication 
(1952): “Equally important as disease carriers are flies and roaches.” 
Yet both can and do carry similar disease-producing viruses, bacteria, 
protozoa, and helminths. Cockroaches and house flies are potential 
health hazards to man because they feed on both human feces and 
human food. Their relative importance as vectors is largely related 
to their abundance and the access each has to feces or other infective 
material and food or human contact. Flies, diurnal, more active, and 
at times apparently more numerous than cockroaches, frequently con- 
taminate food during its preparation or after it has been served. 
Cockroaches, nocturnal, less active, and less obvious than house flies, 
usually contaminate unprotected food in dark storage areas or food 
left exposed overnight. Unfortunately it has always been easier to 
