152 QUEENSLAND AGRICULTURAL JOURNAL. [1 Fes., 1898. 
Entomology. 
THE DISSEMINATION OF YEASTS BY INSECTS. 
Tue part played by insects in the distribution of minute vegetable organisms 
has been made the subject of an interesting investigation by Dr. Amedeo 
Berlese at the Portici Laboratory for Agricultural Chemistry. That they do 
perform this task, often a very mischievous one, has long been known ; but 
the Professor, as is shown in the current number of Nature, has proved that, 
for good or eyil, they are more active than had been hitherto ascertained. 
Ants were the subjects of his first experiments. He had frequently detected 
the cells of two alcoholic yeasts hidden in fissures of the bark on the trunks 
of both fruit and forest trees. These he suspected to have been transported: 
by the ants, which were constantly travelling up and down the trunks, and it 
seemed likely that flies might co-operate in the work. First he “put the 
question” to the ants. He collected a large number of a species which is ver 
common in vineyards. They were allowed access to bunches of grapes whic 
had been carefully sterilised, and afterwards placed under conditions that 
prevented the possibility of any introduction of moulds or yeasts from the 
outer air, The result, in less than a fortnight, was that all the bunches which 
the ants could visit were abundantly infested with yeasts and moulds; while 
several others which had been preserved, even for a much longer time, in 
sterilised vessels from which the ants were excluded, had neither moulds nor 
yeasts nor bacteria on their surfaces. Dr. Berlese then turned his attention 
to the flies. His methods of inquisition, we fear, would not be approved 
by those who share Corporal Toby’s view, and are merciful even to 
the house fly and the blue-bottle. In fact, these torments of the 
human race must have had a decidedly bad time in the laboratory. The 
first experiment, however, was simple and humane. A number of bits 
of sterilised meat were set out on a terrace, some of them covered by 
wire gauze, others accessible to the flies. After two hours’ exposure to them 
and thirteen to the air, yeasts were found to be much more abundant in the 
former; indeed, Dr. Berlese estimates that the quantity of yeasts conveyed 
by flies is about twenty-six times as great as is brought by the air. Similar 
experiments were made with grapes, and with similar results. The next point 
to settle was the precise way in which the transport was effected. It was first 
ascertained that ferments were often more frequent in the bodies of flies than 
on their legs and feet; next, cells similar to those of yeast were detected in 
their excreta. It remained, then, to study the passage of these cells through 
the digestive apparatus of the insect. Common blue-bottles, or meat flies, 
were selected for this purpose, and a large number of experiments were 
made on them; but scme other flies and cellar-midges were also tested. 
It was proved in all cases that when the flies were fed with sterilised 
material the exereta contained no yeasts; but when they had a diet 
of pure cultures of sundry yeasts, the excreta soon contained in great 
quantities the yeasts that were in the food. These cells also were not dead, 
but living. If collected, they duly germinated and developed, though the rate 
of the process and the abundance of the result were found to depend to a 
considerable extent on the temperature maintained. Further experiments 
indicated that the cells increased in number in passing through the body of 
the fly, and the general result of the whole series was to demonstrate that ants 
and certain flies play an important part, not only in the distribution (as was 
already known), but also in the preservation and multiplication, of alcoholic 
ferments. Insects, in fact, contribute far more than atmospheric air to the 
dissemination of yeasts, which are conveyed internally rather than externally. 
In some cases this distributing agency may be exercised for good, but we 
suspect it is far more often potent for evil.—Standard. 
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