NO. IO COCKROACHES—ROTH AND WILLIS 43 
tolerate the cockroach, which shuns daylight, than to ignore the 
ubiquitous house fly, which breaks bread with us each meal. 
In his discussion of the medical importance of flies, West (1951) 
stated that, “There is acceptable laboratory proof for the transmission 
of approximately thirty diseases (or parasitic organisms) by Musca 
domestica and related forms.” This number was not increased in the 
more recent review by Lindsay and Scudder (1956) on nonbiting flies 
and disease. Cockroaches, by way of comparison, have been shown 
to harbor, naturally or experimentally, about 40 species of pathogenic 
bacteria alone; of these, at least 25 species are Enterobacteriaceae, 
organisms largely responsible for gastroenteritis in man. In addition, 
cockroaches have been shown to be intermediate hosts for many patho- 
genic helminths and to carry helminth eggs, viruses, protozoa, and 
fungi. Obviously, the number of disease agents transmitted is not 
alone a true measure of the relative importance of a vector. In citing 
these figures, we are not implying that cockroaches are medically more 
important than filth flies. Which vector is more important is academic, 
as there is little likelihood that the question can ever be resolved. 
Although modern sewers do not promote fly breeding, they are ideal 
habitats for cockroaches where these insects may breed and become 
contaminated with feces and from which they may spread into nearby 
buildings (see pp. 10, 15). However, where the disposal of human 
waste is more primitive, filth flies may be the important vectors. 
Feces deposited on the soil certainly attract more flies than they do 
cockroaches. Feces deposited in privies may be visited more readily 
by cockroaches than by flies, according to the particular situation. 
Sanitary pit privies have in the past reduced the fly menace, as 
flies in general tend to shun dark places and the deeper the pit, the 
fewer the flies (Fair in Rosenau, 1940). However, this is no longer 
wholly true. Kilpatrick and Bogue (1956) observed that, contrary to 
the general opinion prior to 1950, exceedingly heavy emergence of 
house flies has recently been recorded from active privy pits. This 
they attributed to a physiological change in house-fly behavior that 
they correlated with the development in the fly population of resistance 
to the insecticide dieldrin. 
Dark privy pits might be expected to be ideal cockroach shelters, as 
attractive to these insects as sewers. Dow (1955) and Kilpatrick and 
Bogue (1956) have reported that in the southwest United States cock- 
roaches were very prevalent in privy pits that had not been treated 
with insecticides. The ecology of cockroaches in privies has yet to be 
explored. Such a study should yield interesting information. Haines 
