Oak Timberworm (Arrhenodes minutus) - Male
Oak Timberworms are sexual dimorphic (i.e. males and females do not look the alike). Males have broad and flat, pincer-like mouthparts while females have long slender snouts. Females use their snouts to chew tiny holes in various hardwoods. They oviposit one egg in each hole, then usually seal the hole with a sticky secretion and frass. Oak Timberworms -- which are actually beetles -- are attracted to wounds on living trees and oviposit only on exposed sapwood. Both sexes feed on sap at wound sites.
(Note: Jim McClarin has an excellent series of photos showing a female boring a hole and ovipositing posted on BugGuide.)
Egg incubation requires anywhere from a few days to three weeks, depending upon temperatures. Newly hatched larvae bore directly into the wood. That's when the real damage to the timber begins. Typically, tunnels are bored nearly straight across the wood grain with little up or down slope. Tunnels go almost to the opposite side of the tree, make a sharp U-turn, and go back across the wood grain toward the entrances. Larvae keep the tunnels clean by pushing the frass outside. Pupation occurs near the tunnel exit from which the adults emerge. The life cycle is generally 3 years, but some individuals develop in 2 years and a few require 4 years.
Known hosts trees include oak, elm, popular and beech. Many other hardwoods including boxelder, honeylocust and aspen are suspected of being susceptible to infestation. These beetles also serve as vectors for oak wilt fungus. They range throughout most of eastern North America from Canada to the Gulf of Mexico.
Oak Timberworms are sexual dimorphic (i.e. males and females do not look the alike). Males have broad and flat, pincer-like mouthparts while females have long slender snouts. Females use their snouts to chew tiny holes in various hardwoods. They oviposit one egg in each hole, then usually seal the hole with a sticky secretion and frass. Oak Timberworms -- which are actually beetles -- are attracted to wounds on living trees and oviposit only on exposed sapwood. Both sexes feed on sap at wound sites.
(Note: Jim McClarin has an excellent series of photos showing a female boring a hole and ovipositing posted on BugGuide.)
Egg incubation requires anywhere from a few days to three weeks, depending upon temperatures. Newly hatched larvae bore directly into the wood. That's when the real damage to the timber begins. Typically, tunnels are bored nearly straight across the wood grain with little up or down slope. Tunnels go almost to the opposite side of the tree, make a sharp U-turn, and go back across the wood grain toward the entrances. Larvae keep the tunnels clean by pushing the frass outside. Pupation occurs near the tunnel exit from which the adults emerge. The life cycle is generally 3 years, but some individuals develop in 2 years and a few require 4 years.
Known hosts trees include oak, elm, popular and beech. Many other hardwoods including boxelder, honeylocust and aspen are suspected of being susceptible to infestation. These beetles also serve as vectors for oak wilt fungus. They range throughout most of eastern North America from Canada to the Gulf of Mexico.
