Search Nature Watch

Tuesday, August 6, 2019

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!