SCIENCE AND INDUSTRY. 
Wales was at one time attributed to the presence of mites. Other causes 
meet with more favour now. In the case of the vine, however, erinose 
is due to the presence of the mite Phytoptus (Eriophyes) vitis, and a 
similar condition occurs on pear leaves. The relations which insects 
ney bear towards diseases due to micro-organisms may be stated as 
ollows :-— 
I. Mrecuanicarty Carrtep (Externan Transmission). 
The infective organism may be picked up by the insect on external — 
parts of its body, e.g., legs, or outer mouth parts, where it may retain its 
virulence for some time. ; 
(a) The organism may then be directly inoculated, as into 
wounds made by the insect carrier; or 
(b) the organism may be accidentally sown from the insect’s 
body under such conditions that infection follows. 
IJ. Actrrvery Carrirep (Internat Transmission). 
The micro-organism may be taken up by an insect during feeding, 
and passed along unharmed in the alimentary tract. 
(c) If the infective principle is merely taken into the body, 
and without change or multiplication passed out in the 
normal way, we have Mechanical internal transmission. 
(d) If the infective principle develops or multiplies within the 
insect body, and finally reaches a part from which it 
may be successfully transferred to its alternate host, we 
have Biological internal transmission. 
~ TI1T.—Inprrecr Assocration. 
An insect, though not itself carrying infection, may cause wounds, ~ 
through which parasitic micro-organisms, brought there by other 
agencies, find easy access into the plant or animal body. 
T. Mecwanicarty Carrimp. 
(a) Directly Inoculated. 
The mechanical external carriage and inoculation of pathogenic 
organisms by insects is very common among animals and plants. Fire 
Bhght of the apple and pear, caused by Bacillus amylovorus, was the 
first plant disease shown to be bacterial in nature, by Burrill in 1880. 
Waite also demonstrated clearly that bees and other insects carried the 
pacillus from flower to flower. He proved experimentally that they carry 
the disease organisms, which multiplied in the nectar of the flowers. 
Wasps and ants also spread the disease. Waite observed 40 species 
of insects visiting pear blossoms, and many were proved experimentally 
to be carriers. 2B. amylovorus was repeatedly isolated from the mouth 
parts of bees. Direct insect relation was clearly proved, and insects 
not only disseminate the disease germs, but also actively puncture the 
tissues, and so introduce the disease. Other insects concerned are 
aphids, leaf-hoppers, bark-boring beetles (e.g., Scolytus), and a plant 
bug (Lygus). The germs may remain viable for many days in honey 
and in honey-dew of aphids. The wilt of Solanaceous plants due tuo 
Bacterium solanacearum was experimentally transmitted by Erwin 
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