Celticecis spiniformis

Distinguished from other Celticecis species by the elongated, spiniform (thorn-shaped) gall structure rather than rounded or pouch-like galls. The galls of C. spiniformis are narrow, pointed, and often occur in dense clusters on leaf undersides and along veins, unlike the irregular, wart-like galls of C. capsularis or the rounded, nipple galls of C. celtiphyllia. Adult midges require microscopic examination for definitive identification.

Adults are small, delicate flies typical of gall midges, with long, slender legs and reduced wing venation. The larvae are maggot-like, legless, and develop within the gall tissue. The gall itself appears as a slender, pointed, thorn-like projection emerging from hackberry leaf veins or petioles, often clustered and ranging from green to reddish-brown depending on age.

Associated with hackberry trees (Celtis species), particularly in deciduous woodlands, forest edges, riparian corridors, and urban plantings where host trees are present. The species is tied to the presence of its host plant rather than specific abiotic conditions.

Eastern North America, ranging from the Great Plains eastward to the Atlantic coast, and from southern Canada through the central and eastern United States. Distribution corresponds closely with the range of Celtis occidentalis and Celtis laevigata.

Adult emergence occurs in spring, coinciding with hackberry leaf flush. Gall development is visible from late spring through summer, with mature galls persisting on fallen leaves into autumn and winter.

Larvae feed on gall tissue induced on hackberry leaves; the nutritional relationship appears to be utilization of plant tissue modified by the gall induction process rather than direct tissue consumption. Adults do not feed or feeding habits are unknown.

• Celtis occidentalis - gall inductionprimary host
• Celtis laevigata - gall inductionprimary host

Eggs are deposited on developing hackberry leaves. Larvae induce gall formation and develop within the spiniform structure, feeding on nutritive gall tissue. Pupation occurs within the gall. Adults emerge through a small exit hole. The species likely has one generation per year (univoltine), with larvae overwintering in fallen leaves.

Females oviposit on young hackberry foliage, triggering localized plant growth that forms the characteristic thorn gall. Larvae remain sedentary within the gall throughout development. No complex social behaviors or dispersal patterns have been documented.

As a gall inducer, modifies host plant tissue to create a protected microhabitat and food source for its larvae. The galls may provide shelter for other arthropods, including inquilines and parasitoids. Impact on overall tree health is generally minimal, though heavy infestations may cause localized leaf distortion.

Occasional nuisance in ornamental hackberry plantings due to unsightly gall clusters. No economic importance; not a pest of cultivated crops. Sometimes used in educational contexts to demonstrate plant-insect interactions and gall induction. No medical or forensic significance.

• Celticecis capsularisAlso induces galls on hackberry, but produces irregular, wart-like or capsular galls rather than the slender, pointed thorn galls of C. spiniformis.
• Celticecis celtiphylliaInduces small, rounded, nipple-shaped galls on hackberry leaves, distinct from the elongated spiniform galls of C. spiniformis.
• Celticecis ovataProduces oval or globular galls on hackberry, differing in shape from the thorn-like projections of C. spiniformis.

• gall midge
• hackberry
• Celtis
• plant gall
• Cecidomyiidae

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• GBIF taxonomy match
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• NCBI Taxonomy
• Catalogue of Life