Bodacious Borers

Cottonwood Borer

As spring turns into summer in Central Texas, the heat brings out some of our most interesting creatures, most notably the native wood-boring beetles.  This group encompasses many species and families of beetles, all of whom eat wood either in their larval or adult form.  Most often they are found in or around dead or dying trees, as they are vital players in enabling the turnover of weak trees with strong ones, and acting as primary decomposers of wood which allows for the recycling of nutrients back into the soil.

One large family of beetles in the wood-boring group is the longhorn beetles, or Cerambycidae, typically characterized by their extremely long antennae which are often as long or longer than the beetle’s body.  Their family scientific name comes from the mythological Greek shepherd Cerambus, who was turned into a large beetle with horns after an argument with nymphs.  Three of the more noticeable wood-boring longhorn beetles in our area include the Banded Hickory Borer (Knulliana cincta), Cottonwood Borer (Plectrodera scalator), and Texas Bumelia Borer (Plinthocoelium suaveolens plicatum).

Banded Hickory Borer

With a body length of up to 1.4 inches, the Banded Hickory Borer is a fairly slender, typically gray to reddish-brown beetle with a pair of pale marks near the base of the elytra or wing covers that are sometimes absent, and tiny spines at the ends of the elytra.  Eggs are laid by the adults in bark crevices or directly into hardwoods such as oak, pecan, walnut, willow, and hackberry, upon which their larva feed.  In their first season, the larva feed just beneath the bark, then head deeper into the wood as they develop, a cycle which takes two to three years to complete.

Cottonwood Borer

The Cottonwood Borer is an elongate, unmistakably robust beetle with black and white markings that are formed by contrasting areas of white pubescence or fine short hairs on black body parts.  At a body length of up to 1.6 inches, the summer-active adults lay eggs in August and September on cottonwood and willow, where larva bore into the base and overwinter.  After two or three years to reach maturity, they pupate in chambers beneath the bark and emerge as adults in late spring, and are often found feeding on new shoots, leaf petioles (stems), and the bark of their host trees.

Texas Bumelia Borer

One can hardly miss the bright iridescence of the metallic green Texas Bumelia Borer, with its contrasting reddish-orange and black legs. The larva of this species feed on gum bumelia and mulberry, developing in the roots and trunks of these host plants.  With a body length of 1.5 inches, the adults are diurnal and often found on the trunks of their host plants, although they typically feed on flower nectar and are attracted to lights.

Despite their large size, most native wood-boring beetles are not pests.  Instead, they take advantage of dead and dying trees and aid in the natural decomposition process. As you venture out and about this summer, see if you can find some of these bodacious borers!

A Different Kind of Longhorn

Cottonwood Borer

The Cerambycidae are a family of longhorn beetles, typically characterized by extremely long antennae, often as long as or longer than the beetle’s body.  Also called longicorns, over 400 species have been described in Texas alone.  The scientific name of this beetle family is named after the shepherd Cerambus, a mythical Greek figure who was transformed into a large beetle with horns after an argument with nymphs.  Most of these beetles can fly well and are found on tree trunks, logs, flowers, or come to lights at night.  Some even squeak as a defense mechanism when held, making a rocking motion with their head which rubs tiny ridges against the inside surface of their thorax.

Cottonwood Borer

Two of our more common longhorn beetles are the Cottonwood Borer (Plectrodera scalator) and the Long-jawed or Horse-bean Longhorn Beetle (Trachyderes mandibularis).  The Cottonwood Borer is one of the largest insects in North America, reaching 1.6 inches in length and 0.5 inches in width.  It has a bold black and white pattern on its body with long black antennae.  The white portions of the pattern are actually microscopic masses of hair.  Adults are active by day, feeding on leaf stems and shoots of cottonwood trees.  The female bores small holes in the base of the tree to lay her eggs.  The larvae take up to 2 years to mature, then they pupate for about 3 weeks in a root below ground, and once metamorphosis is completed they chew their way out of the root and dig their way to the surface.

Long-jawed Longhorn Beetle

Long-jawed Longhorn Beetle has a glossy black or dark brown body with 4 generally large but sometimes reduced yellow to yellow-orange markings, and segments of its antennae and legs alternating between black and yellow-orange.  It can grow to a length of 1.3 inches, and is generally common from March to November.  Its species name comes from the fact that the males have much expanded jaws or mandibles. Active during the day, adults are mostly found near wounded trees as they feed on oozing sap, and its larvae feed on native hackberries as well as non-native ficus and tamarisk species.

Goes fisheri

One of the subfamilies of the Long-horned Beetles is the Lamiinae, or Flat-faced Longhorns.  This includes the 9 New World species in the Goes genus, one of which is rare and endemic to Central Texas.  This species, Goes fisheri, was first described in 1941, but does not have a common name.  Beetles in this genus are typically twig girdlers or stem borers, although the food plant of G. fisheri is currently unknown.  It is distinguished from a more common species, G. pulcher, or the Hickory Borer, by the grayish pubescence of its elytra or wing covers.  G. fisheri is just over 1 inch long, not including its antenna, appears to be nocturnal in its habits, and is attracted to artificial light. 

This large family of longhorns includes beetles called sawyers, pruners, and girdlers in addition to borers.  Most are found in dead or dying wood, and some mine live plants.  While many of these beetles are considered to be occasional pests, it should be noted that they literally help shape the forest canopy and assist in recycling dead wood into precious soil.  All the more reason to appreciate this different kind of longhorn!