[Illustration: FLOWERING SPRAY OF DIOSCOREA RETUSA.]
One of the most elegant plants one can have in a greenhouse is this
twiner, a native of South Africa. It has slender stems clothed with
distinctly veined leaves, and produces a profusion of creamy white
fragrant flowers in pendulous clusters, as shown in the annexed
engraving, for which we are indebted to Messrs Veitch of Chelsea, who
distributed the plant a few years ago. On several occasions Messrs
Veitch have exhibited it trained parasol fashion and covered
abundantly with elegant drooping clusters of flowers, and as such it
has been much admired. When planted out in a warmish greenhouse and
allowed to twine at will around an upright pillar, it is seen to the
best advantage, and, though not showy, makes a pleasing contrast with
other gayly tinted flowers. It is so unlike any other ornamental plant
in cultivation, that it ought to become more widely known than it
appears to be at present.--_The Garden._
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RAVAGES OF A RARE SCOLYTID BEETLE IN THE SUGAR MAPLES OF
NORTHEASTERN NEW YORK.
About the first of last August (1882) I noticed that a large
percentage of the undergrowth of the sugar maple (_Acer saccharinum_)
in Lewis County, Northeastern New York, seemed to be dying The leaves
drooped and withered, and finally shriveled and dried, but still clung
to the branches.
The majority of the plants affected were bushes a centimeter or two in
thickness, and averaging from one to two meters in height, though a
few exceeded these dimensions. On attempting to pull them up they
uniformly, and almost without exception, broke off at the level of the
ground, leaving the root undisturbed. A glance at the broken end
sufficed to reveal the mystery, for it was perforated, both vertically
and horizontally, by the tubular excavations of a little Scolytid
beetle which, in most instances, was found still engaged in his work
of destruction.
At this time the wood immediately above the part actually invaded by
the insect was still sound, but a couple of months later it was
generally found to be rotten. During September and October I dug up
and examined a large number of apparently healthy young maples of
about the size of those already mentioned, and was somewhat surprised
to discover that fully ten per cent. of them were infested with the
same beetles, though the excavations had not as yet been sufficiently
extensive to affect the outward appearance of the bush. They must all
die during the coming winter, and next spring will show that, in Lewis
County alone, hundreds of thousands of young sugar maples perished
from the ravages of this Scolytid during the summer of 1882.
Dr. George H Horn, of Philadelphia, to whom I sent specimens for
identification, writes me that the beetle is _Corthylus
punctatissimus_, Zim, and that nothing is known of its habits. I take
pleasure, therefore, in contributing the present account, meager as it
is, of its operations, and have illustrated it with a few rough
sketches that are all of the natural size, excepting those of the
insects themselves, which are magnified about nine diameters.
The hole which constitutes the entrance to the excavation is, without
exception, at or very near the surface of the ground, and is
invariably beneath the layer of dead and decaying leaves that
everywhere covers the soil in our Northern deciduous forests. Each
burrow consists of a primary, more or less horizontal, circular canal,
that passes completely around the bush, but does not perforate into
the entrance hole, for it generally takes a slightly spiral course, so
that when back to the starting point it falls either a little above,
or a little below it--commonly the latter (see Figs. 1 and 2).
[Illustration: FIGS. 1 and 2--Mines of Corthylus
punctatissimus.]
It follows the periphery so closely that the outer layer of growing
wood, separating it from the bark, does not average 0.25 mm. in
thickness, and yet I have never known it to cut entirely through this,
so as to lie in contact with the bark.
From this primary circular excavation issue, at right angles, and
generally in both directions (up and down), a varying number of
straight tubes, parallel to the axis of the plant (see Figs. 1, 2, and
3). They average five or six millimeters in length, and commonly
terminate blindly, a mature beetle being usually found in the end of
each. Sometimes, but rarely, one or more of those vertical excavations
is found to extend farther, and, bending at a right angle, to take a
turn around the circumference of the bush, thus constituting a second
horizontal circular canal from which, as from the primary one, a
varying number of short vertical tubes branch off. And in very
exceptional cases these excavations extend still deeper, and there may
be three, or even four, more or less complete circular canals. Such an
unusual state of things exists in the specimen from which Fig 3 is
taken.
[Illustration: FIGS. 3 and 4--Mines of Corthylus
punctatissimus.]
It will be seen that with few exceptions, the most important of which
is shown in Fig 4, all the excavations (including both the horizontal
canals and their vertical off shoots) are made in the sap-wood
immediately under the bark, and not in the hard and comparatively dry
central portion. This is, doubtless, because the outer layers of the
wood are softer and more juicy, and therefore more easily cut, besides
containing more nutriment and being, doubt less, better relished than
the drier interior.
This beetle does not bore, like some insects, but devours bodily all
the wood that is removed in making its burrows. The depth of each
vertical tube may be taken as an index to the length of time the
animal has been at work, and the number of these tubes generally tells
how many inhabit each bush, for as a general rule each individual
makes but one hole, and is commonly found at the bottom of it. All of
the excavations are black inside.
The beetle is sub-cylindric in outline, and very small, measuring but
3.5 mm in length. Its color is a dark chestnut brown, some specimens
being almost black. Its head is bent down under the thorax, and cannot
be seen from above (see Fig. 5).
[Illustration: FIG 5.--Corthylus punctatissimus.]
Should this species become abundant and widely dispersed, it could but
exercise a disastrous influence upon the maple forests of the
future--_G. Hart Merriam, M D, in American Naturalist._
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