The hackberry bark-beetle (Scolytus muticus), the elm barkbeetle (Hylastinus rufipes), the mulberry bark-beetle (Phloephthorus frontalis), the ash bark-beetle (Meliobius aculeatus), (see Fig. 3), and a number of others of this large class of beetles were noted, but, though they may sometimes be quite injurious, are more often secondary enemies which infest and damage only injured or weakened trees and prevent their immediate recovery.

Fig. 3.

BARK-BORING

GRUBS OF OAKS, CHESTNUTS, BIRCHES AND
POPLARS.

Much injury to the above-named forms has been reported from surrounding regions. Indeed, for a number of years losses have been experienced from boring grubs, but no such large bodies of timber have been killed in any one year as to excite special attention. Individual trees, however, die throughout the forests every year and contribute to the annual losses. At different periods in some of the southern States chestnuts and oaks scattered over extended areas have died in alarming numbers.

Upon investigation made in different sections it was found that the oak-destroying bark-borer, or two-lined chestnut borer (Agri

lus bilineatus), was directly associated with the cause of this wide destruction of trees.

The adult of this ravaging enemy is a slender blue-black beetle, with a faint yellow line along the middle of each wing cover. The larva is a long, slender, flat-headed grub, which, upon hatching from the egg deposited in the outer bark, burrows into the inner bark, through which it eats long zigzag mines. When this insect occurs in great numbers in a tree, the inner bark is killed and the tree readily dies. The insect passes the winter in the larval stage in the outer portion of the inner bark, where in the spring it transforms to the adult. The beetles begin to emerge in May and June. They deposit their eggs in the outer bark of living trees, or stumps of recently felled trees, oak and chestnut, or in other places where lightning and fire have made inroads for them. They are often found breeding in countless numbers in the bark of stumps, and in this manner are enabled to increase in such rapidly multiplying numbers as to enable them to attack and kill living trees.

This is a form which should be closely guarded against in Indiana forests. Especially in the southern counties where oak and chestnut abound. At present it is not doing noticeable damage to live, healthful trees, but the conditions existing in many wooded tracts visited by the writer suggest the possibility of an attack by this insect. Many scattered chestnuts which have long passed the age of maturity and are consequently decreasing in value are rapidly becoming breeding places for many such destructive forms. Not only chestnut but many other forms such as oaks, beech and maple are found in a similar condition.

METHOD OF CONTROL.-The following method of control is taken from a report of the United States Forest Service: "There is evidently only a single generation of this insect annually, and this fact, together with its habit of breeding in the bark of stumps and injured trees, and in those killed by it, with its habit of transforming in the outer bark, suggests a practical method of control. All infested stumps and dying and recently dead trees should be located before the beginning of winter, or by the first of November, in order that the infested bark may be removed from the trunks and stumps and burned before the first of April."

"Trees struck by lightning in May and June furnish favorable conditions for the multiplication and destructive ravages of the two-lined chestnut borer; therefore, all such trees, together with those dying from insect attack, should be felled during the summer or the winter following, and the bark removed and burned. Very

often such trees can be utilized for fuel, so that nothing is lost in the operation."

The cottonwoods, birches, yellow poplar and aspens are often killed or seriously injured by various species of Agrillus, which have habits very similar to and many times identical with, the above described species, and therefore require the same treatment. The work of these insects was noted throughout the State on yellow poplar, cottonwood and some of the oaks, but in no case were they present in dangerous numbers. The curious embossed effect noted on the surface of wood which has been infested by one of these bark-boring insects is the result of healed-over grooves made by larvae in the outer layers of wood beneath the bark. These wounds were made when the tree was in a healthful and growing condition and furnish conclusive evidence that the tree was attacked while living. The burrows are long and winding and suggest the ease with which trees are girdled and killed when thickly infested.

The economic importance of this widely-known insect as affecting the growth of the black or yellow locust (Robinia pseudacacia), is realized by everyone who is interested in this valuable tree. Private plantings as well as natural growths have been utterly destroyed or injured to such an extent that urgent need of all available information concerning the nature of its work is plainly evident.

CHARACTER OF THE INSECT AND ITS WORK.

The borer is a whitish, elongate, so-called "round-headed" grub or larva (Fig. 4, D), which hatches from an egg deposited by a black or brown and yellow-striped long-headed winged beetle (Fig. 4, C), found on the trees and on the flowers of golden-rod from August to October. The eggs are deposited in the crevices of the bark of living trees from August to October, and on hatching the young borers mine into the outer portion of the living inner bark, where they pass the winter. In the spring they bore through the bark into the sapwood and heartwood. Here they transform in July and August to pupae and in August and September to adult beetles. These beetles soon emerge from the trees and deposit eggs for the next generation of borers and beetles.

The injury to the trees (Fig. 4, A and B) consists of wounds in the bark and sapwood which, if sufficiently severe or repeated year after year, result in either a stunted growth, or the death of the

Fig. 4. Work of the Locust Borer: A, section of the main stem of a young tree, showing length of burrow in which a larva developed and transformed to the adult beetle; B, section of a branch showing enlargement at point of injury; C, male beetle; D, larvae, dorsal view. Drawings from specimens collected six miles west of Ft. Wayne, on the farm of J. H. Gerding. For photograph of planting from which specimens were taken, see Fig. 25, p. 74.

young and old trees. The numerous worm holes in the wood also reduce its commercial value or render it absolutely worthless.

The presence of the insect in injurious numbers is indicated by the frequency of the beetles on the golden-rod flowers and on the locust trees, from August to October; by the slight flow of sap and by the borings where the young larvae are at work in the bark during April and May; by the whitish sawdust borings lodged in the rough bark, and on the ground around the base of the trunk during May, June and July, and by the breaking down of the branches and young trees and by the sickly appearance of the young tender twigs and leaves in July and August.

OCCURRENCE AND EXTENT OF DAMAGE.

The insect was found in each of the nine counties mentioned in this report, and in most cases the damage from its attacks was considered injurious. It was found on both young and old trees, and so extensive was the damage to natural growths, artificial plantings, and shade trees, that in some sections, and, indeed, over the greater part of the State, it is considered unprofitable to grow the tree for shade or timber. Often in such sections the natural sprout growth is considered a pest rather than otherwise.

The loss resulting from defective timber, stunted growth, and the death of trees was found to be considerable, and could be represented by the difference in value between the damaged growth or product and the same if uninjured and healthy. It is readily seen that this, if expressed in dollars, would amount to a large

sum.

METHOD OF CONTROL. The following suggestions have been taken from various authorities and are thought to be of practical value in the control of this insect in both artificial plantings and natural growths.

The fact that the young larvae from eggs deposited during summer remain in the outer bark during the winter and do not enter the wood until the following May, suggests that if locust trees known to be infested were cut between November and May, the bark removed from that portion which is of value, and the remainder burned, it would destroy vast numbers of the insects and aid greatly in protecting the remaining trees. The infested trees may be easily detected during May, June and July by the ejected. sap and borings. These trees, being once located, should be cut close to the ground and burned, before the first of August, to de