151 
The cesophagus is not more than 1 millimeter in diameter. The insect 
begins the process of separating the fibers of the tree by means of its 
chisel-like teeth. The rapidity with which a beetle can work is shown by 
the fact that within half an hour it will have entered a fourth of its own 
length into the plant tissue, and when once it is enabled to brace its 
strong-spined legs against the walls of the burrow its progress is accel- 
erated. The heart of the tree is its objective point. 
On Plate V are shown successive layers of leaf petioles at the heart with the 
burrow of an adult which finally reached the center. Figs. 1, 2, 3, and 4, respec- 
tively, show the pieces from outside, inward. 
An examination of the fibers as soon as they are cut by the beetle dem- 
onstrates them to be almost dry, which renders it more probable that the 
purpose for which they are taken into the mandibles is solely to extract 
their juice, after which they are expelled from the mouth. Plate V, fig. 4, 
shows the heart of the coconut tree with a beetle at work. The bits of 
tissue which have been chiseled off can plainly be’seen. In less than ten 
minutes the insect had burrowed into the soft substance for a distance of 
10 millimeters. Plate III, fig. 2, shows the initial work of a beetle in a 
leaf petiole. 
The beetles fly only at night; in the daytime they are readily found in 
their burrows. Their wings are quite large and the wing muscles in the 
thorax are strong and adapted for the flight of such heavy, unwieldy 
insects. In the interspaces between the intestines and the reproductive 
organs the abdomen is filled with air sacs and trachee. 
Hrtent and character of damage done.—It is rare to find a single coco- 
nut tree anywhere in the Philippines which does not show one or more 
evidences of attack by this beetle. It is the pest most frequently reported 
by farmers and coconut growers, and in hundreds of trees which I have 
personally examined large holes in the trunk, distorted leaf stems, or rag- 
ged leaves demonstrate the character of its work. The insect larva or the 
adult, in its work inside the tree, frequently cuts off the tip of the embryo 
leaf or the tips of the leaflets on one or both sides of the midrib, so that 
when the leaf finally grows it appears as if it had been trimmed with a 
pair of shears or as if a triangle had been cut from one or both sides. 
The fibers severed by the insect protrude from its burrow, giving the latter 
a ragged appearance. During the daytime the beetles are frequently 
encountered in very old holes, into which they evidently have gone for 
the purpose of hiding. ‘They have never been seen further to excavate 
these old cavities. The openings which are made serve to allow rain 
water to enter the tree, where it causes a most rapid decay of the interior, 
and they also serve as an entrance for other insects quite as destructive 
as the coconut beetle. 
Distribution.—Oryctes rhinoceros Li. is probably tropicopolitan, being 
found in Honduras, India, Ceylon, Java, the Philippines, Celebes, Borneo 
