^34 
Insects and Disease 
of the filariae from the thoracic muscles forward into the head and “beak” 
of the mosquito. He has seen a filaria larva issuing from a fine opening 
near the tip of the labium. According to Bancroft’s theory the filaria 
escapes from the beak of a puncturing mosquito into the skin of a man, 
finishes its development and growth in the skin, becomes adult, pairs and 
produces embryos which get into the lymphatic spaces or vessels, and are 
carried by the lymph into the blood. Here they circulate over the body, 
finally lodging in the lymphatic glands and causing the characteristic hyper¬ 
trophy of tissue. Further investigation is necessary, however, before the 
question of transmission is fully understood. That the mosquito is the 
actual disseminating agent of the disease is, however, certain. 
The species of mosquito which acts as intermediate host and distributing 
agent of the filariae in Australia is Culex jatigans, var. skusii. Anopheles 
rossii is also known to carry the filariae. In Samoa, where elephantiasis 
is more prevalent than anywhere else in the world, I have found the most 
abundant mosquito to be Stegomyia fas data, the same species that spreads, 
yellow fever. This species is also the most abundant mosquito in the Hawaiian 
Islands, and is indeed wide-spread over the tropics and subtropics of the 
whole world. If, as is probable, it is the principal carrier in Samoa of the 
filariae that cause elephantiasis, it is the most formidable single species among 
all the insect scourges of mankind. 
In this brief account of the role played by certain insects in the propa¬ 
gation and dissemination of certain human diseases only a small part of the 
story, as already known, has been told. Cockroaches, bedbugs, and other 
household insects are being found to be hosts for the germs of other familiar 
diseases. A host of investigators is at work; reports of discoveries are being; 
published constantly, and in a few years our knowledge of this causal rela¬ 
tion of insects to human disease will fill books instead of chapters. 
