Pachypsylla celtidisvesicula

Distinguished from the closely related Pachypsylla celtidismamma (hackberry nipplegall psyllid) by the gall morphology produced by its nymphs: blister-like galls rather than nipple-shaped galls. Adults are small, approximately 3.5–4.5 mm in length, with a body plan resembling tiny cicadas. They possess beak-like piercing-sucking mouthparts and can be confused with barklice (Psocodea), which differ in having chewing rather than piercing-sucking mouthparts. Wing pads are visible in late-instar nymphs. Adults of different Pachypsylla species are morphologically similar and often require association with their characteristic gall type for reliable identification.

Associated with hackberry trees (Celtis spp.), occurring wherever these host plants grow naturally or as ornamentals. Nymphs develop within leaf galls. Adults overwinter in concealed microhabitats such as cracks in bark, building crevices, and other sheltered locations.

North America, with records spanning much of the continental United States and southern Canada. Documented from Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Montana, Maryland, Mississippi, Missouri, North Carolina, North Dakota, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, and Texas.

Adults emerge from galls in late summer to fall, with peak nuisance aggregations on buildings occurring during this period. Adults overwinter and become active again in spring when female psyllids deposit eggs on newly unfolding hackberry leaves. Timing of oviposition is critical and must coincide precisely with leaf emergence from buds.

Nymphs feed on plant sap within the protective gall tissue induced on hackberry (Celtis spp.) leaves. Adults feed on plant sap using piercing-sucking mouthparts, though specific host tissues are not documented.

• Celtis - gall inducerNymphs induce blister-like galls on leaves; multiple Celtis species utilized

Females deposit eggs on hackberry leaves during bud break in spring. Nymphs hatch and feed, inducing the formation of blister-like galls as a plant response. The nymph develops through five instars within the gall, with the final instar possessing visible wing pads and posterior spike-like projections used to cut an exit. Adults emerge from galls in late summer to fall, seek overwintering sites, and re-emerge the following spring to reproduce.

Nymphs are sedentary, developing entirely within their individual galls. Adults are capable of jumping to escape threats, a trait common to psyllids. In fall, adults seek sheltered locations for overwintering and can aggregate in large numbers on building exteriors, window screens, and door frames. This aggregating behavior is temporary and poses no threat to humans or structures.

Nymphs act as gall inducers, creating specialized microhabitats on hackberry leaves. The galls provide food and shelter for the developing psyllid and incidentally support a community of parasitoids including species of Psyllaephagus (Encyrtidae) and Torymus (Torymidae), which develop by parasitizing nymphs within galls.

Adults can become a temporary nuisance pest when they aggregate on building exteriors in fall seeking overwintering sites. They pose no structural damage, bite, or disease risk; physical removal with water is sufficient for control. The species is not an agricultural or forestry pest.

• Pachypsylla celtidismammaStrongly resembles P. celtidisvesicula as an adult; distinguished by inducing nipple-shaped rather than blister-like galls on hackberry leaves
• Other Pachypsylla speciesSix additional species occur on hackberry in North America, each producing a characteristic gall type; adult morphology is similar across species requiring gall association for identification
• Cecidomyiidae (gall midges)Some gall midges also induce galls on hackberry; distinguished by gall morphology and by rearing to adult stage

• gall insect
• psyllid
• hackberry
• Celtis
• North America
• nuisance pest
• overwintering aggregation
• parasitoid host
• Aphalaridae
• Sternorrhyncha
• Hemiptera
• jumping plant louse
• leaf gall
• blister gall

• BugGuide
• Wikipedia
• GBIF taxonomy match
• Catalogue of Life
• Encyrtid Holdings | Entomology Research Museum
• Bug Eric: Hackberry Psyllids: A Fixture of Fall
• Bug Eric: Blacklighting Already?