Horntail Woodwasp: Identification and Why Control Is Rarely Needed

What Is That Large, Wasp-Like Insect in Your Yard?

If you've spotted a striking, elongated insect with a prominent "stinger" (actually an ovipositor) hovering around trees or lumber, you're likely seeing a horntail—also called a woodwasp. Despite their intimidating appearance, these insects are harmless to people and rarely require control.

Key Identification Features

• Cylindrical body, 1–1.5 inches long
• Long, spear-like ovipositor on females (not a stinger)
• Often black, brown, or metallic blue with yellow/red markings
• Loud, buzzing flight
• Larvae are white, cylindrical grubs with a short spine at the tail end

Biology and Behavior

Horntails are primitive wasps (family Siricidae). Females use their ovipositor to drill into weakened, dying, or recently cut wood—especially conifers—and lay eggs. The larvae tunnel through the wood for 1–3 years, feeding on fungi they cultivate. They do not attack healthy, living trees.

The sirex woodwasp (Sirex noctilio) is an invasive species that can attack living pines, but it's not widespread in all regions. Most horntails encountered are native species targeting stressed wood.

Management

No control is needed in most cases. Horntails are secondary invaders—their presence indicates the wood was already compromised. If they emerge from firewood indoors, simply vacuum them up. For structural timber, kiln-drying or proper seasoning prevents infestation.