Important leaf sucking insects include species of aphids and plant lice including " ( Monellia spp . " and " Monelliopsis spp . ), " which suck the juices from leaves and often deposit a sticky substance called " honey-dew " on the leaf surface that may turn black and prevent photosynthesis; and the walnut lace bug " ( Corythucha juglandis ), " which causes damage when the adults and nymphs suck the sap from the lower surfaces of walnut leaflets.
