VOL. VI. OCTOBER, 1870. No. 4.
[Translated for the American Bee Journal.]
Origin of Honey Dew.
In No. 11 of the Bienenzeitung for 1870, the Baron of Berlepsch urges
bee-keepers to make diligent observations, to ascertain the origin of
honey dew. I have for many years given special attention to the subject,
as it is one of great interest, not only to bee-keepers, but also to
pomologists. My observations fully corroborate the remark of the Baron,
that honey dew occurs, in most cases, independently as a vegetable
excretion, and only occasionally as the product of aphides. On last
Sunday, June 19th, I had an opportunity to assure myself definitely of
the correctness of this position. On that day, as early as seven o’clock
in the morning, I received a visit from Mr. Heuser, of Westom, one of
the intelligent apiarians who compose the Ahrweiler Association for
Bee-culture. While we sat conversing about bees, a lad came to inform us
that he had, the evening before, seen a fine swarm clustered on a large
pear tree. We naturally hastened to the spot, but found that the swarm
had already decamped. A loud humming among the branches, however, led us
to suppose there might be a hollow limb somewhere, into which the bees
had retreated, and friend Heuser was induced to climb up in search of
it. He found none, but observed a multitude of bees busily engaged
licking up the honey dew with which the leaves of the tree were
covered--being evidently an exudation, for on the most careful
examination we could not find a single aphis, though on the morning of
the next day thousands of aphides were observable there.
It remains for me to mention the state of the weather at the time, for
according to my observations this chiefly conditions the production of
honey dew. On Saturday, June 18th, the weather was oppressively hot.
Towards evening the wind began to blow from the northwest; and the night
was cool, though without dew on the grass. This necessarily checked the
circulation of sap, which I regard as the primary cause of honey dew,
for I may state explicitly that I never saw any, except when hot days
were followed by a sudden and great reduction of temperature. The same
observation was made, many years ago, by an aged bee-keeper in
Niederheckenbach, who, whenever he notices in summer a sudden change of
weather, at night, from great heat to cold, will rise at three or four
o’clock in the morning and close the entrances of his hives; as he is
firmly persuaded that the honey dew certain to come, will be injurious
to his bees. I must confess that honey dew has not always proved
beneficial to our bees. In some cases they seemed to be sickened by it,
and to remain so for nearly a week, as indicated by their inability to
fly. This was more especially the case at an apiary which I had in an
oak forest, where bark was largely stripped and dried for tanners’ use.
I am unable to account for the occurrence, and must leave chemists to
determine whether the consumption of _tannin_ had aught to do with it.
Whenever honey dew occurs in my neighborhood again I will strip leaves
from various trees affected by it, and send them for examination to Dr.
Keermrodt, of Bonn, the chemist of the Agricultural Experimental Union
of the Rhine province.
The views of Prof. Hallier, that the honey dew produced by aphides is of
great practical account in bee-culture, I am not prepared to endorse.
During the summer of 1869 I was a student in the Pomological Institute
at Reutlingen, and very seldom saw a bee on any twig covered with
aphides, yet we were there sorely annoyed by those parasites. Even now,
I am compelled to use soapsuds, &c., to rid my plants of these unwelcome
visitors, yet I have never seen a bee among them.
Your readers will probably be interested in learning the views of two of
the most eminent pomologists, regarding the origin of honey dew.
Court-gardener Jager, of Eisenach, writes as follows to Regel’s
Garden-Flora:--“According to my observations, honey dew is much more
frequently exuded from the leaves of plants than produced by aphides. I
regard honey dew, in many cases, as _a segregation of the saccharine
portion of the juices of plants, which these are then no longer able to
excrete out of their organism by means of the blossoms_. I was led to
adopt this view by repeatedly observing that linden trees so kept under
by pruning that they never blossom, excrete such a superabundance of
honey dew that such as is not gathered by insects, drips from the leaves
to the ground, and is often collected on boards and bottled. Linden
trees which are allowed to blossom, do indeed likewise produce honey
dew; but I have never seen it on trees that bloomed profusely, and as I
live in the midst of lindens, I have the best opportunities for
observation.”
Entered according to Act of Congress, in the year 1870, by Samuel
Wagner, in the office of the Librarian of Congress, at Washington.
Next, my own respected teacher, Dr. Lucas, of Reutlingen, remarks, in a
note on the foregoing passage--
“This observation of our esteemed friend Jager certainly deserves
attention. Whether he is entirely right or not, is to me not altogether
clear. I have seen honey dew indiscriminately on young trees and on old
of various kinds; but always only after we had several successive hot
and dry days, followed by dewless nights. It is very probable that then
the juices of plants become more concentrated, and thus more highly
charged with saccharine, in so much that drops of liquid sweet may exude
through the pores of the leaves, and that then the aphides will quickly
resort to the tables thus ready decked for them, and multiply with
almost incredible rapidity, is a natural phenomenon observable in the
case of other insects also. But that the aphides are the originators of
the honey dew, as many foresters and others maintain, can certainly not
be accepted as correct and true.”
Allow me, in conclusion, to request bee-keepers and pomologists to watch
for the appearance of honey dew on the occurrence of such weather and
temperature as above indicated, and to communicate the result of their
observations.