Psyllid

Psyllids, sometimes called jumping plant lice, are small sap-feeding insects in the superfamily Psylloidea within the order Hemiptera, the true bugs. Despite the misleading common name, they are not related to true lice at all; instead they are more closely related to aphids and cicadas, sharing the piercing-sucking mouthparts typical of the group.

Most psyllid species are highly host-specific, feeding on only one or a few closely related plant species throughout their life cycle. Many produce distinctive waxy or sugary secretions, and some induce galls or leaf curling on their host plants as they feed. A well-known example is the Asian citrus psyllid, which feeds on citrus trees and is notable for vectoring a bacterial disease of citrus.

Psyllids are found on nearly every continent, with particular diversity on eucalyptus, citrus, pear, and other woody plants. Their populations can build quickly in warm weather, and heavy infestations may cause curled, distorted, or yellowing foliage on ornamental and agricultural plants.

• Adults are 2-5 mm long, with a wedge-shaped body and clear or patterned wings held roof-like over the back.
• Strong jumping hind legs give them a cicada-like or leafhopper-like appearance in miniature.
• Antennae are relatively long and thread-like compared to the small body.
• Coloring ranges from pale green or yellow to brown or mottled, often matching the host plant's foliage.
• Nymphs are flattened, scale-like, and often coated in waxy filaments or a sugary secretion called "lerp" in some species; they are far less mobile than adults.
• Lookalikes include aphids and leafhoppers, but psyllids' strong jumping ability and cicada-like wing posture help distinguish them.

Psyllids occur wherever their host plants grow, from temperate gardens and orchards to subtropical and tropical woodlands. They are especially diverse on eucalyptus in Australia, citrus in warm climates, and pear and other rosaceous trees in temperate regions. Nymphs remain fixed on leaves or stems, while winged adults can disperse short distances by jumping or flying to find new host plants, typically most active in the warmer months.

Psyllids feed exclusively on plant sap, using needle-like mouthparts to tap into leaf or stem tissue. This sap feeding can cause distorted growth, leaf curling, yellowing, or the formation of galls in some species, and heavy infestations are recognized as pests of certain crops and ornamentals. Many psyllids excrete honeydew or waxy secretions that can attract ants and support the growth of sooty mold on leaves below. In natural ecosystems, psyllids are prey for lady beetles, lacewings, spiders, and parasitoid wasps, forming a link in garden and forest food webs.

Females lay small stalked eggs on leaves or stems of the host plant. Nymphs hatch and pass through five instars, remaining largely stationary while feeding and often producing protective wax or a sugary lerp covering. After the final nymphal molt, winged adults emerge and disperse to mate and find new host plants. Depending on species and climate, psyllids may complete several generations per year, with some species overwintering as adults in bark crevices or leaf litter.