Aulacidea tumida (Bassett, 1890)

Nomenclature: Aulax tumidus Bassett, 1890 | Aulax sonchicola Ashmead, 1896 | Aulacidea solidaginis Girault, 1903

Feeds on: Induces galls on Lactuca canadensis L.

Distribution: United States: Massachusetts, New Hampshire, Virginia

Aulacidea tumida

Fusiform pithy stem swellings high on the stem of Lactuca canadensis, bearing many leaves or branches. Dia up to 30 mm.

[Photo caption]

345. On Lactuca canadensis. Adults emerged May 15-27; May 25-27 (DC).

Aulax sonchicola, new species.

Four specimens, reared during June, 1887, from a gall occurring on the stem of a species of wild lettuce, Sonchus oleraceus, found at Asheville, North Carolina, by the writer. In my own collection are specimens collected in Canada.

Aulacidea tumida
Lettuce tumor gall wasp

Hosts: Canada lettuce (Lactuca canadensis) and possibly prairie lettuce (L. ludoviciana).

Gall location: On the stem, often toward the apex but occasionally further down on the stem.

Description: Extremely variable. The most common appearance for these galls is as large, 3-5 centimeters in diameter, round, and many-chambered, sometimes baring leaves and branches. Occasionally, they are more spindle-shaped, or instead appear as smaller galls, barely-swollen and gnarled. Green and fleshy when fresh to brown and rough when old and dry.

Range: The known range for this species is from southern Quebec south to Virginia and west to Minnesota and Arkansas.

Due to the tremendous variability of this gall, its taxonomy is rather uncertain. Another described species, Aulacidea annulata, is almost certainly a synonym of A. tumida; Aulacidea annulata is currently associated with the spindle-shaped, irregular galls, but ongoing taxonomic studies will likely validate this synonymy in the near future. Similarly to the cryptic lettuce stem gall wasps, museum specimens indicate that the Canada lettuce stem gall wasp may also occur on prairie lettuce (L. ludoviciana), but this claim remains unsubstantiated

Aulacidea tumida (Bassett)

Aulax tumidus BASSETT
Aulax tumida DALLA TORRE
Aulacidea tumida KIEFFER
Aulax timidus JARVIS
Aulax sonchicola ASHMEAD
Aulacidea sonchicola KIEFFER
Aulacidea solidaginis GIRAULT

Gall. (Plate XXIV, Figs. 1-8.) On the stalks of wild lettuce (Lactuca canadensis), usually near the summit and often in the panicle, and then covered with short flower stalks. Polythalamous. More or less rounded or elongate irregular swellings of various shapes. Green when fresh and brown when old and dry. Inside (Fig. 8) the gall is pithy and contains numerous larval cells: Length, 25-75 mm.

Habitat: Canada; New England and Middle States, southward and westward.