RELATION OF INSECTS TO DISSEMINATION OF DISEASES. 
conditions favorable for their development. Ergot (Claviceps pur- 
purea), which is now found on many cereals and grasses in New South 
Wales, exudes a glistening saccharine liquid very attractive to flies, 
which carry the spores both on their body and internally, depositing 
viable spores in their feces. A disease that does not yet oceur in Aus- 
tralia, Peanut Leafspot, due to Cercospora personata, has been widely 
spread in the United States of America by grasshoppers. One of the 
commonest diseases of the tomato is Early Blight (Alternaria solani), 
and the spores of this, in addition to those of the other common leaf 
blight (Septoria lycopersict), have been found in the excreta and on the 
bodies of the larye and adults of the Colorado Potato Beetle (Leptino- 
tarsa), and the tomato worm (Protoparce) by American investigators, 
and no doubt these two common diseases here are widely spread by 
beetles, aphids, and worms. Flea beetles (Hpitrix) are also active dis- 
tributors. 
IL. (d) Biological Internal Transmission. 
In this method, the infective principle persists within the insect, and 
undergoes multiplication or some further stage of development. Many 
of these processes are complicated and difficult to investigate. They 
include diseases due to Protozoa, filterable viruses, bacteria, and fungi. 
Of the Protozoan diseases, malaria is one of the best known. Our 
health authorities are somewhat concerned about the possible spread 
of the disease in Australia. We have both the source of infection— 
many returned soldiers who are still suffering from the presence of the 
parasite in their blood—and the transmitter of the disease, the Anophe- 
line mosquito (not yet recorded as infected in Australia), in whose diges- 
tive parts the Plasmodium can pass through its sexual development. 
Should one of these mosquitoes héeome infected by sucking the blood 
from an infected person, the parasite (Plasmodium malarve) will go ° 
through certain stages of its life cycle, and may then infect any healthy | 
Person whom the mosquito bites. Somewhat similar diseases are The 
Sleeping Sickness of man caused by two or more species of Typanosomes, . 
T. rhodesiense in South Central Africa, transmitted by the fly Glossinu 
morsitans and. T. gambiense, less virulent than the former and more 
generally distributed by the fly (tsetse) Glossina palpalis. 
African Relapsing Fever is caused by a Spirochete (S. duttond), 
and the transmission is through the bite of an argasine tick (Ornitho- 
dorus moubata). The tick also transmits the infection to its progeny. 
They hide in the cracks and in the mud floors of the old native huts 
and bite the sleeping inmates, or the material from the feces and the 
Coxalglands when rubbed into wounds, cause infection. Another dreaded, 
disease is Yellow Fever, transmitted by a mosquito Aedes calopus.. The 
infective principle belongs to the group known as Filterable Viruses. 
Among both animals and plants there are many diseases of this nature, 
and if there are any living organisms they are either too small to be - 
Seen, or our methods are not capable of revealing them. The infective 
_ principle, or “contagium” as it has been also named, is able to pass 
through any of the fine filters that are capable of preventing the 
Passage of the smallest known organism, Thesé diseases of plants 
are commonly named Mosaics or Chloroses, and their number is con- — 
"nually increasing. In America, many have been definitely proved to 
C.19077—3 657 ; 
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