Lobiopa undulata

on a Saw-tooth Oak (Quercus acutissima) that was oozing sap.

Sap-Feeding Beetles
Oak wilt is a serious fungal disease that kills thousands of oak trees in the United States each year. Sap beetles are attracted to fresh wounds on oaks and to the sweet smell of oak wilt spore mats that grow under the bark of diseased trees. The beetles can transmit the oak wilt fungus to fresh wounds on healthy oak trees, leading to new infections. Pruning healthy oaks during the growing season increases the chance of sap beetles infecting them with oak wilt. To prevent oak wilt, avoid pruning or wounding oak trees in the spring and summer when spore mats are present and the beetles are the most active. - https://extapps.dec.ny.gov/docs/lands_forests_pdf/oakwiltposter.pdf