Insects Active at night

Broad-necked Root Borer

Prionus laticollis

iNaturalist Wikipedia

A heavy-armored titan of the summer night, the Broad-necked Root Borer is one of the most impressive beetles you can discover in your own backyard. Known for its serrated antennae and powerful build, this nocturnal wanderer is a fascinating glimpse into the hidden world of forest giants.

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Quick Identification

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Size

Adults typically measure 22–45 mm (0.9–1.8 inches) in length, with females being significantly larger and bulkier than males.

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Colors

Deep mahogany brown to shiny black; antennae are dark and segmented, with males possessing more prominent, serrated segments.

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Key Features

Broad, flared prothorax with three distinct sharp teeth on each side
Robust, heavy-set body with a glossy, armored appearance
Large, deeply notched (serrated) antennae, especially in males
Strong mandibles capable of pinching if handled

When You’ll See Them

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Activity pattern Active at night

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Peak hours 9 PM - 2 AM

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Season June-August

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Diet Adults rarely feed, while larvae (grubs) are wood-borers that consume the roots of deciduous trees including oak, apple, poplar, and chestnut.

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Habitat Deciduous forests, mature orchards, and suburban yards with established hardwood trees.

public Geographic range

Where Does the Broad-necked Root Borer Live?

Native to the North American continent, the Broad-necked Root Borer is a prominent resident of the eastern half of the United States and southeastern Canada. Its core territory extends from the southern reaches of Quebec and Ontario, stretching down the Atlantic coast to Florida, and reaching as far west as the wooded regions of Oklahoma and Arkansas. They are particularly common in the Appalachian corridor and the temperate broadleaf forests of the Midwest.

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2 Countries

4.2M km² Range

Least Concern Conservation

US United States CA Canada

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iNaturalist / Verified observation data

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Behavior

The Broad-necked Root Borer is a nocturnal giant that spends the vast majority of its life hidden from human eyes. While the larvae live underground for several years, the adults emerge during the mid-summer months with a single-minded focus: reproduction. They are most active on humid summer nights, where they can often be found crawling along the forest floor or clumsily flying toward artificial light sources.

Despite their somewhat intimidating appearance and large size, these beetles are not aggressive toward humans. Males are more active fliers, searching for the pheromones released by the heavier, often flightless females. Because the adults have a very short lifespan—lasting only a few weeks—they rarely feed, living instead off the energy reserves they accumulated as larvae.

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Camera Tips

To capture the Broad-necked Root Borer on camera, timing and lighting are everything. Since these beetles are highly attracted to light (phototactic), the best method is to set up your AI camera near an external light source, such as a porch light or a specialized UV 'blacklight' trap. Positioning the camera to face a white sheet illuminated by a light will often result in the beetle landing directly in the frame, providing clear, high-contrast shots of their armored bodies.

Because females are heavy and frequently crawl rather than fly, try placing one of your cameras at ground level near the base of old oak trees or rotting stumps. Set the camera to a macro or close-focus mode if available, as these insects are relatively small compared to mammals but large for insects. A low angle will capture the impressive 'toothed' detail of their thorax and their formidable mandibles.

Since they are most active during the warmest, most humid nights of mid-summer, check your camera frequently during July. Set your trigger interval to its shortest setting, as these beetles can be quite clumsy and may tumble out of the frame quickly. If you are using a trigger-based AI camera, ensure the sensitivity is high enough to detect the movement of a large insect at close range.

Similar Species

Species that look similar or are commonly confused with Broad-necked Root Borer.

Tile-horned Prionus

The Tile-horned Prionus has even more antennae segments (12-13 or more) which overlap like roof tiles, and its prothorax is less wide.

Palo Verde Root Borer

Found primarily in the Southwest, it is much larger and thinner, with longer legs and a different host tree preference (Palo Verde trees).

Brown Prionid

Usually lighter in color and more slender, with less pronounced spines on the sides of the thorax.

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Frequently Asked Questions

Broad-necked Root Borers are strictly nocturnal. They typically emerge shortly after dusk and are most active during the darkest hours of the night, usually between 9 PM and 2 AM, especially when the air is warm and humid.

The easiest way to attract them is by using light. They are highly drawn to UV lights or standard bright porch lights during the summer months. Maintaining mature deciduous trees like oaks or maples also provides the necessary habitat for their larvae to thrive underground.

As adults, they eat very little, if anything at all, focusing entirely on mating. However, their larvae are 'root borers' that spend several years underground chewing on the roots of various hardwood trees and shrubs.

Yes, they are very common in suburban areas that have established landscaping. If your neighborhood has older trees or is located near a patch of woods, you likely have these beetles nearby even if you rarely see them.

Look closely at the 'neck' (pronotum) area; it is very wide and features three distinct sharp spines on each side. Additionally, their antennae are thicker and more saw-toothed than many other similar-looking beetles.

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