Celticecis spiniformis

Cecidomyiaceltis spiniformis
Cecidomyia unguicola New synonym.
Celticecis unguicola

Hosts. Celtis occidentalis, reticulata, laevigata, tenuifolia

Gall. On leaf lamina, usually on underside of leaf, often in groups; upright-conical; base flared, circular, flat to rounded; tapering evenly from base to sharply pointed apex; surface hairless, glabrous, green, turning yellow to tan; 4–6 mm high and 3–4 mm wide at base; connection to leaf circular, flat, ca. 1/3 width of gall base; apparent on opposite side of leaf as slight, sometimes discolored convexity; gall in cross section of variable thickness beneath and around base of subcylindrical larval chamber, thinning abruptly between distal third and fourth, at which level gall apex breaks off upon adult emergence in spring.

Affinities. — Nine species of Celticecis appear to form a natural group: C. spiniformis, C. aciculata, C. acuminata, C. capsularis, C. conica, C. cupiformis, C. pilosa, C. subulata, and C. supina. All form galls on the leaf lamina except for C. supina whose galls are attached to veins, usually minor ones.

Biological notes. Galls reach their ultimate length as a narrow cone before the base broadens to its full width, so young galls can at first be confused with those of C. subulata. The gall only later spreads out considerably at the base, which can be acute to well-rounded in cross section. When full-grown, the larva spins a cocoon that extends only to the narrow part of the larval chamber where the tip of the gall will break off in spring. Galls were already evident in late March in central Louisiana on only partly expanded leaves and were first noticed already with second instars in early May in Maryland. At least some full-grown larvae had already formed cocoons in mid-June in Louisiana and late June in Maryland. Many galls still with second instars can be found through mid-July so growth appears staggered. Some galls with cocooned larvae may remain attached to the leaves into September in Maryland and into November in Louisiana where the leaves remain on the tree longer. This longer duration on the leaves is a habit shared by most of the nine species of the C. spiniformis group, unlike most galls of the remaining species that tend to dehisce as soon as the larvae have formed their cocoons.

Distribution (Map 18). — Celticecis spiniformis is a common, widespread species in the eastern half of the U.S., except in Florida where it is conspicuously absent. It is known from northern hackberry, sugarberry, dwarf hackberry and reticulated hackberry.

AR, GA, IL, IO, KS, KY, LA, MD, MS, MO, NY, OH, PA, SD, TN, TX, VT, VA, WV, WI; absent in FL

- Raymond J. Gagne, John C. Moser: (2013) The North American Gall Midges (Diptera: Cecidomyiidae) of Hackberries (Cannabaceae: Celtis spp.)^©

Reference: https://www.biodiversitylibrary.org/page/51467028#page/41/mode/1up