My son while farming with a man near Dearborn, found one in the river bottoms. He didn’t know what he found, and when he sent the image, I was so excited. I told him what it was and asked him to bring it home to me…he had already left the area and couldn’t go back…sigh! See what I mean?
The cottonwood borer is a type of beetle referred to as longhorn beetles. They are classified in the family of insects called Cerambycidae. The name comes from the shepherd Cerambus, the mythical Greek figure who was transformed into a large beetle with horns after an argument with nymphs. The long horns of Cerambus are equated to the long antennae of beetles in this family, who’s antennae may be as long or longer than their bodies. In the case of the Cottonwood Borer their antennae are usually a bit longer than their overall body length. This is impressive considering, this beetle is capable of reaching lengths up to 1 ¾ inches and a width of a half inch! They are black and white with a pattern that reminds me of the classic pattern in women’s fashion called houndstooth. The white portion of the pattern is actually masses of microscopic white hairs, and each beetle has its own unique pattern of white that acts similarly to the fingerprint in humans.
Like their name suggests, their host plant of choice is the cottonwood. They will also use poplar and occasionally willow or sycamore. The female chews small pits into the base of the tree where she lays her eggs. The eggs hatch and the young larvae begin chewing and feeding their way to the heartwood of their host. It takes up to two years for them to complete their lifecycle to adult. When they are ready to pupate they make their way to an underground root and remain there for three weeks before chewing their way out of the cocoon and digging their way to the surface. Once they have reached the surface, the adults have approximately two months to feed, mate and lay eggs before they perish.
The feeding habits of the larvae can damage young trees. Girdling the tree is the biggest threat to trees, also known as ring-barking, which removes or injures the trunk of the tree or other woody plant being fed on. Girdling prevents the tree from sending nutrients from its foliage to its roots overtime. It will also prevent flow of nutrients in the other direction depending on how much of the xylem is removed. Zylem’s basic function is to transport water from the roots to the stems and leaves, and also transports nutrients. This feeding activity weakens young trees making them susceptible to wind damage. Large mature trees usually receive no damage from their feeding activity. Cottonwood Beetles will feed on recently felled trees and act as decomposers who recycle important nutrients back into the soil. Adults typically feed on leaf stems and the bark of tender shoots, occasionally causing flagging.
Like most things in nature, I prefer to find the beauty in all creatures. For me this beetle is stunningly beautiful and has so far eluded me at every turn. If anyone happens to see one of these impressive beetles, keep in mind they can bite if mishandled, but do give me a call…please!
All photos of Cottonwood Borers provided by K. Leeker.
