Several insects attack hickory but rarely become epidemic. The forest tent caterpillar ("Malacosoma disstria"), walnut caterpillar ("Datana integerrima"), and walkingstick ("Diapheromera femorata") may defoliate individual trees or limbs. Sucking insects, including aphids (Monellia spp.), feed on the underside of leaves, causing them to curl and drop prematurely. The twig girdler ("Oncideres cingulata") may seriously prune seedlings and even large trees by girdling the terminal and branches. The hickory bark beetle ("Scolytus quadrispinosus") can be troublesome during dry years and periods of stress.