mone 
an especial nuisance to citrus crops and at one time also well established 
in that State, apparently has been completely eradicated now. 
One of the most serious threats to this country in recent years has come 
from the giant African snail, Achatina fulica, This voracious eater with 
an enormous reproductive capacity began its immigration from East 
Africa via human agencies about the turn of the 19th century. Inthe in- 
tervening years this snail has spread to India, Ceylon, the mainland of 
China, and the East Indies. Its dispersal in the Pacific Islands, nearly de- 
nuding some of them, was greatly facilitated during World War II by the 
rapid conquest of this area by the Japanese. They introduced the snail as 
a supplemental food source to many new places including New Guinea, New 
Britain, and New Ireland. The snail was introduced into Hawaii in 1936 
and has subsequently cost the taxpayers some $200,000 for control meas- 
ures, not accounting for the damage to plants inthat area. In 1948 it was 
brought to California on returned war equipment, but an intensive cam- 
paign prevented its introduction. Nevertheless, constant vigil must be 
maintained to insure that it is not introduced again to become established. 

Medical Importance to Man and His Domestic Animals 
Snails, as required intermediate hosts in the life cycle of parasitic tre- 
matode worms infecting man and his domestic animals, occupy a position 
of utmost importance in man's war against disease. Their role as neces- 
sary living quarters for the developing larval parasitic worms indirectly 
implicates them as being responsible for some of the most serious and 
economically important human communicable infections. 
Only relatively few snails are of medical importance, although nearly 
every kind of mollusk is inhabited by some form of worm parasite. Of 
these, almost all live in fresh water. The worm parasites of importance 
to man and which require larval development in a snail are commonly re- 
ferred to as blood flukes, lung flukes, or liver flukes, depending on the 
part of the body they infect. 
Bilharziasis, 2lthe human blood fluke disease, is rapidly replacing malar- 
ia as the major communicable malady of man, Progress in the control of 
this disease has not kept pace with that of other infections and, consequent- 
ly, incidence of this disease is on the rise. Conservative estimates of the 
number of people infected now exceed 200 million, None of the species of 
snails that carry the larval blood flukes, such as Pomatiopsis (Oncome- 
lania) hupensis, P, (Katayama) quadrasi, and P, (Katayama) nosophora in 
the Orient, Planorbina glabrata in the West Indies and tropical South Amer- 
ica, and Biomiehealaric boissyi, Bulinus truncatus, and Physopsis africana 
2/ Often referred to as schistosomiasis after the generic name of the 
human blood flukes, Schistosoma 

