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Flat-Headed Wood Borer

   Metallic wood-boring beetles (or flat-headed borers)(Coleoptera: Buprestidae)  


Life History & Ecology:

Coleoptera (beetles and weevils) is the largest order in the class Insecta.  As adults, most beetles have a hard-bodied and boat shaped,with short antennae, a dense exoskeleton that covers and protects most of their body surface.  These are beautiful beetles with distinctive metallic colors (green, blue, bronze, copper).  Larvae are cream-colored and legless with widened, flattened body segments just behind the heads.  Consequently, when these larvae tunnel beneath bark or into the sapwood they produce oval or 
flattened tunnels in cross section.   Galleries are often winding and packed with frass.  Tunneling activities can girdle trunks and branches.  Many species of flat-headed borers occur in the state.  Most are secondary invaders.  The front wings, known as elytra, are just as hard as the rest of the exoskeleton.  They fold down over the abdomen and serve as protective covers for the large, membranous hind wings.  At rest, both elytra meet along the middle of the back, forming a straight line that is probably the most distinctive characteristics of the order.  During flight, the elytra are held out to the sides of the body where they provide a certain amount of aerodynamic stability.
Both larvae and adults have strong mandibulate mouthparts.  As a group, they feed on a wide variety of diets, inhabit all terrestrial and fresh-water environments, and exhibit a number of different life styles.   Many species are herbivores -- variously adapted to feed on the roots, stems, leaves, or reproductive structures of their host plants.   Some species live on fungi, others burrow into plant tissues, still others excavate tunnels in wood or under bark.  Many beetles are predators.  They live in the soil or on vegetation and attack a wide variety of invertebrate hosts.   Some beetles are scavengers, feeding primarily on carrion, fecal material, decaying wood, or other dead organic matter.   There are even a few parasitic beetles -- some are internal parasites of other insects, some invade the nests of ants or termites, and some are external parasites of mammals.
Distinguishing Characteristics:
- Head sunk deepy into thorax and eyes unusually large.
Antennae usually short and saw-toothed.
- Tarsal formula 5-5-5.
- Many species metallic or bronzed particularly on ventral surface.
- Bullet shaped with tapering posterior end.
- 2-40mm in length.
                                                                                                                               Figure 2.  Larvae of round-headed borer (left) and
flat-headed borer (right with cross sections  of tunnels (above).
Examples of f lat-headed borers include the bronze birch borer (Agrilus anxius), uncommon in Texas because of the lack of host trees; Agrilus species found on oak and raspberry (A. bilineatus and A. ruficollis, respectively); f lat-headed appletree borer (Chrysobothris femorata) and a closely related species that attacks recently transplanted or stressed shade, pecan and fruit trees.
Figure 3.  Metallic wood-boring beetles or flat-headed                                                                                                                                 borer adults:   Agrillus bilineatus (left); flat-headed                                                                                                                                 appletree borer (right).   
Bark Beetles (Coleoptera: Scolytidae)
Beetles in this group tunnel below the bark of trees and/or into the wood. Adult beetles are small and reddish-brown to black. Larvae are cream-colored grubs without legs. One member of this group, the European elm bark beetle (Scolytus multistriatus), is the carrier of Dutch elm disease. It occurs in the Texas panhandle, but is infrequently encountered in other parts of Texas.               


There are around 15,00 known species of Buprestidae most of which are tropical with only 120 or so occuring in Europe.

Eggs are laid in crevices on bark and upon hatching the larvae bore under the bark or into the wood creating a winding series of tunnels known as a gallery. The larvae then remain in these galleries until pupation. The larvae of some species also tunnel in herbaceous plants and some species induce gall formation. The larvae are given the common name of 'flat-headed borers' due to their large, flat expanded thorax.

Biology and Habits:

The boat-shaped adult Buprestis lineata has a metallic sheen, hence it’s often called the “metallic” wood borer.  The elytra (wing covers) usually have brightly colored (brick red to yellow) irregular markings and roughened ridges.  The adults usually measure ½ to ¾ inch in length.

Fertilized females deposit their eggs in the cracks and crevices in the bark of tree trunks or limbs.  The legless larvae, typically cream in color, have well-developed, flattened plates on the upper and lower surfaces on the prothorax.  The abdominal segments are small.  Larval development may take two years or more.

Larvae bore under bark and then into sapwood, and can penetrate the heartwood.  Their feeding activity creates extremely flattened galleries (tunnels) and frass consisting of fine sawdust-like borings and pellets.  Typically, galleries under bark edges cover the outer sapwood in a serpentine design.  The walls of the galleries are a scarred with fine, transverse lines somewhat like, but more coarse than, those in old house borer galleries.  Frass from this feeding activity is salt-and-pepper colored.  This fine frass may remain packed in the galleries even after the wood is processed.

Upon completion of its larval development, a larva constructs an elongated pupal chamber near the surface of the wood.  The emerging adult cuts the characteristic flattened oval exit hole, up to ¼ inch long in diameter, to escape from the wood.  Emerging adults can damage uninfested materials, such as roofing, drywall and flooring that cover infested lumber or logs.  Attack in dry wood is uncommon.


Infestations are rarely recognized until the adults emerge.  Since reinfestation is minimal, remedial treatments are not normally necessary.  For the most part, economic losses are incurred before the wood is graded and built into a structure.

Additional damage to the structure may occur when the galleries function as water channels, capturing rainwater and channeling it inside the wood, creating a condition conducive for decay.  Seal emergence holes to prevent water damage to wooden members. 

Trees give us so much, oxygen, shade, beauty, shelter and value to our
homes, it makes good sense to do all we can to protect our trees from harm. 

Contact: cell: 830.257.8871
                     Jim Rediker - Nurseryman -  Arborist  - TDA Certified

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