INTRODUCTION 13 
walked, fed, and upon which they deposited infected feces. 
Roberts (1934) found that larvae of Phaenicia pallescens would 
ingest eggs of Ascaris, that these eges would survive pupal meta- 
morphosis of the fly, and that such eggs are passed with the fecal 
droppings of the adult. These data are supported by the findings 
of Pipkin (1942-1943). 
Serological evidence leads Shope (1936-1938) to consider 
that ‘‘the virus of swine influenza is a surviving prototype of 
the agent responsible for the great human pandemic of 1918.’ 
If this is true, hogs and earthworms may serve as the source of 
future epidemics. He suggested that there might be a sapro- 
phytic transformation of the virus in either the swine lungworm, 
a fairly common parasite in the bronchioles of hogs, or in the 
earthworm, the alternate host of this nematode. _ 
Earthworms may prove to be the animal reservoir of both 
swine and human influenza. The swine lungworm may be the 
vector of influenza to hogs and the clusterfly (Pollema rudis) 
the vector to man. This blowfly is an important insect parasite 
of earthworms, and it sometimes occurs in tremendous numbers 
in human habitations during fall and winter months. These 
factors in the origin and transmission of human influenza have 
not been investigated. 
The following organisms have been recovered from adults of 
common blowflies, Tuberculosis (Mycobactertum tuberculosis), 
Tularemia (Pasteurella tularense), Undulant Fever (Brucella 
abortus), and various species of trypanosomes and Leishmanias. 
They may be vectors of eye diseases such as acute conjunctivitis 
and/or of skin diseases such as yaws. 
MYIASIS. Laake stated that ‘‘Myiasis is the term used when 
referring to the presence of and the resulting disturbance caused 
by fly larvae living parasitically on the tissues of man and other 
animals.’’ Myiasis may be classified anatomically according to 
the portion of the body affected, for instance, cutaneous or sub- 
cutaneous, cavity or wound, intestinal, nasal, aural, rectal, 
ophthalmic, ete. | 
Flies may be placed conveniently in several categories accord- 
ing to the time of the occurrence of their larvae in wounds. The 
condition of a wound is somewhat indicative of the species of 
blowfly larvae which may infest it. 
Primary Flies cause Specific Myiasis. Larvae of such flies are 
obligate tissue parasites. They initiate wounds in man and 
animals, are able to infest areas of unbroken skin, and may infest 
already existiug lesions. 
Secondary Flies cause Semi-Specific Myiasis. Larvae of such 
