The hackleberry gall psyllid for example , causes a woody gall on the leaf petioles of the hackleberry tree it infests .
The nymph of another psyllid produces a protective lerp out of hardened honeydew .
The hackleberry gall psyllid for example , causes a woody gall on the leaf petioles of the hackleberry tree it infests , and the nymph of another psyllid produces a protective lerp out of hardened honeydew .