Cottonwood Borer

"Adult beetles can be found on and around host plants during the summer. They are large (1 1/4 inch long), robust longhorned beetles with black antennae as long or longer than the body. The body is beautifully marked with a bold pattern of black rectangular areas on a creamy white to yellow background. Larvae are legless, cylindrical (oval in cross section), creamy-white bodies and brown to black headed, growing to 1 ½ inch long.

There are a great many other cerambycid beetles that attack trees and other plants, but few others have larval stages that feed on roots or are larger than the cottonwood borer. Larvae of root borers, such as the tilehorned prionus, Prionus imbricornis (Fabricius), attack apples, Prunus (peaches, plums, etc.), pears, pecans, poplars, and other trees, by feeding in the crown and larger roots. They develop over a period of 3 to 5 years. Heavily-infested mature trees, particularly in sandy soils, slowly decline and die. Adult beetles are dark brown, over 1-1/2 inches long and their antennae are not as long as the body. They do not feed, are active at night and emerge in June and July."

( Information Source: http://insects.tamu.edu/fieldguide/bimg177.html)