This section is from the book "The Gardener's Monthly And Horticulturist V26", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
As a concluding paper we now reach insect life and influence in a bacterian point of view, and ask, Is it possible that the light tread of a simple fly, mosquito or ant can communicate the bacterian contamina to other sources unsuspected by us? The query in itself looks most uninviting, yet it may be said that giant intellects have not deemed it beneath human thought or observation to trace out the workings of insect life, either for good or evil. Now, it is evident that if the bacterian theory be correct in the case under consideration and as propounded by Professor Burrill in the American Naturalist of July, 1881, may not the trampings, punctures, borings, cuttings, bruis-ings, grindings, and even sawings of some insects, have their due influence and thus leave openings of access for the easy transmission of microscopical germs?
Upon the subject of flies, my own observation touching their movements upon diseased pear trees suggested an article which appeared in the Fruit Recorder of August, 1883, and headed as follows, viz.: "Are the house-fly and blow-fly the scavengers or disseminators of pear blight?" This thought originated from the fact of our frequently seeing flies and even mosquitoes with fixed pro-bosces upon the exuded sap and absorbing it at such a rate of speed that it was both amusing and instructive.
Dr. Thomas Tavlor comes to our aid concerning the capabilities of flies as carriers or propagators of disease in a paper read before the American Association for the advancement of Science. He entrapped several hundred flies to test the point in view. His experiments were with the red rust of grasses and resulted in proof positive that they are capable of conveying such spores to plants and other bodies; but concluded that the larvae of the fly will sometimes consume microscopical germs as well as distribute them. The same investigator also found the suction tube of a fly's proboscis sufficient in diameter to admit of taking up the spores of cryptogams, trichina, etc., as also the eggs of anguillulae, and even the anguillulae themselves, of which there are upwards of one hundred known species; and he found in one case a fly's proboscis containing not less than thirteen.
Dr. Grassi also verifies this experience and reaching beyond by his discovering that flies take up the ova of various worms and again discharge them in their faeces unchanged. He also found many eggs and numerous parasites in the intestines. Virchow in his investigations concerning proboscidian insects in connection with malignant diseases, made insect contamination a study, and says most probably these insects effect inoculation; but flies which make no wound may also implant the poison upon the skin by their soiled wings and feet. If then we behold a goodly number of flies intermingled with mosquitoes energetically consuming the sap exposed to their view and link this with the bacterian contagion, what shall our verdict be in this case, especially when we find them apparently slicking themselves up by the nimble movements of their feet and legs upon their bodies and thus distribute the contaminated sap upon themselves before departing in their winged flights for other fields of mischief.
The mosquito may even show more activity in this direction by its well-known puncture influence. This insect has been studied by men of eminence in China, Australia, India and Egypt, as well as this and other countries, and many diseases are placed to his account upon substantial demonstration; but it is not known whether the poison of the mosquito is saliva, or whether the fever-producing element be a bacillus with which the proboscis is loaded at the time of contact with whatever he may select to deposit his venom. At any rate he is just as likely to disseminate the bacterian contagion as any other insect, when it is stated that a million bacterian germs are capable of resting upon the head of a pin; a few thousand germs would therefore be no impediment in his flights should they have accumulated upon him; and we may here relate on the authority of naturalists that all puncturing, biting and stinging insects are females of their species, so that we may know whenever we send one to "the tomb" when in the act of leaving a " proof impression " upon our bodies, we lessen the prolific sources of insect reproduction.
The bites of some insects are harmless and have no venomous power of their own, but can carry poison from sources of infection to healthy districts that would otherwise have escaped the contaminating influence. The puncture needles of Pasteur would be impotent without first loading them with infective bacteria, and so with proboscidian and other insects as conveyers of disease. They must first mingle with the bacterian germs, the transmission is then readily effected in their movements from tree to tree whenever the proper conditions are met with.
As a reminder of the proper time to watch insect activity in the case of pear blight, those interested should stroll among their trees at the time the sun is rising, the exuded sap is then easily detected at its starting point, and insects are busily becoming insatiated with the offering thus exposed to their instinctive life, and by this means, aided by the sun's rays, the morning supply soon disappears; but other supplies will be forthcoming from morning to morning until the disease has exhausted itself, and to the extinction of the tree's life if this deadly course be allowed to run. From the fact of the sap appearing in the morning and as readily disappearing at this time from the above causes, it would appear that it is not the gentle rays of the morning sun that set bacterian life in motion, but the noonday heat when "up in the nineties," accompanied with warm showers, and thus by infusion with the remaining dry sap present the hotbed of destruction.
At some future time I may offer a supplementary paper upon the newer, and the revival of some older, germicides, bacteriacides, antiseptics and disinfectants that have a direct bearing upon the subject under consideration, for in this field of research our hope of conquering the deadly effects of bacteria is now apparent and demonstrable by such men as Koch, Cohn, Sternberg, and an army of other renowned investigators.
59 Gregory St., Rochester, N. Y. [Dr. Joseph Leidy, the eminent naturalist of Philadelphia, demonstrated years ago by actual observation that diseased matter from sick patients was distributed by the agency of the housefly. This is of interest as a matter of exact knowledge; but there are so many other agents of distribution that one more or less is of little practical account in the great battle. - Ed. G. M].