ARTHROPOD MUSEUM NOTES

Number 90 • January 10, 2012 • Jeffrey K. Barnes

Twig girdler
Order: Coleoptera
Family: Cerambycidae
Genus and species: Oncideres cingulata (Say)

confused flour beetle

During the Arkansas autumn, when it is time to rake leaves, homeowners often notice that there are lots of 1-2 foot twigs on the lawn. Some might blame high winds or squirrel activity. However, if close inspection of the bases of the twigs reveal even, conical cuts, as if produced by miniature beavers, it is the work of beetles known as twig girdlers. Adults are about ½-¾ inch long and grayish-brown with long antennae and a light colored, transverse band on each wing cover, or elytron.  They appear in late summer through early autumn. Normally, females deposit 3-8 eggs singly beneath bark in slits in a terminal or lateral twig. They girdle the twig by chewing a V-shaped groove around its circumference, either causing the twig to break off or hang from the remainder of the branch, a condition known as flagging. Twigs are girdled while the leaves are present, so the severed twigs retain brown leaves for a period of time. It seems that larvae cannot develop in living wood that contains a large amount of sap. Eggs hatch in fall, and larvae remain dormant inside the fallen twigs. In the spring, the larvae feed on the woody portion of the twig while tunneling toward the broken end, leaving the bark intact. Along the way they make small holes in the bark to eject frass. Larval development is complete in late summer, when the gallery is closed off with shredded wood fibers to form a pupation chamber. New adults emerge 12-14 days after pupation. Females live 6-10 weeks and deposit 50-200 eggs each. Common hosts of twig girdlers include hickory and pecan, as well as numerous other shade, nut and fruit trees. Damage can reduce nut yields and cause trees to be severely misshapen.