During the past two seasons the speaker has made special studies of several species of beetles which cut or girdle young hickory trees, or the branches of larger trees, causing the severed part to break off or die. Not fewer than four distinct species of beetles in the east have this habit. Three of the insects do their damage in the larval stage. One of these, _Elaphidion villosum_, has been called the twig-pruner. It is a well known species and its work in pruning the branches of hickory and various other trees has often been referred to. The other two species which sever the wood in their larval stage are _Pseudobidion unicolor_ and _Agrilus arcuatus_. Thus far, these two have no common names. In certain localities they are proving to be very troublesome to both young and bearing trees. In one block of a nursery in Virginia I estimated that the Agrilus larvae had ruined one-hundred dollars worth of young hickory trees. Fortunately, the adult of this species feeds freely on hickory foliage and can be killed readily under nursery conditions by spraying with arsenical poisons. The fourth girdler referred to is our familiar hickory twig-girdler, _Oncideres cingulatus_. In this case the adult insect cuts a ring-like furrow around the wood and the portion above dies. The purpose of the girdle is to provide dead wood in which the young may feed. After the girdle is made, a process which occupies several hours, and, sometimes several days, the eggs are laid in the bark above. In central West Virginia and northward the grubs which hatch from these eggs require two years in which to reach maturity. In the vicinity of Richmond and southward, however, the larvae mature in one year. This more rapid development in the south probably accounts in part for the recent serious outbreak of this insect in Virginia and the Carolinas. Each female beetle is capable of girdling several twigs. One female of about a dozen kept in confinement last autumn made eleven girdles and deposited 55 eggs. Several of the beetles continued their interesting operations until after several snows and severe frosts had occurred. The twig girdler in the beetle stage feeds rather freely on the bark of twigs. Enough of the surface is eaten to justify the belief that the beetles may be killed by spraying with arsenical poisons. This treatment is being tested at the present time. In the cases of all these insects which sever the branches the wood is killed for the safety and comfort of the insect as it undergoes further development above the severed point. There is a period of at least several weeks in each case after the twig dies during which the insect in one stage or another remains in it to complete its growth. This affords an opportunity to gather the twigs and burn them with the assurance that the insects are being destroyed thereby.