Euura exiguae, n. sp.

[Photos of many examples of this gall appear in Figure 31, page 15 of the pdf]

Gall--Exiguoid-type, thin walled, tapering at both ends, outline sinuate or linear, 20-70 mm long X 5-15 mm wide; surface smooth, pubescent or glabrous, but never glaucous; mature gall uniform brown to russet with exit hole plugged with frass made by mature larva before pupating; 1-4 larvae/gall; willow a silvery, racemose shrub usually under 2 m in sandy soil in or along watercourses.

Host.—Salix exiguae Nuttall including ssp. exigua, melanopsis (Nuttall) Cronquist, and synonyms sessilifolia Nuttall (of Jepson 1951, not Cronquist 1964) and hindsiana Bentham; apparently not including ssp. interior (Rowlee) Cronquist, east of Rocky Mountains.

Range.—With the willow at least north of Transverse Ranges up to 750m, probably eastward throughout (Treat Basin to Rocky Mountains up to 2300 m.

Remarks.—Emergence and oviposition, early March through April, both peaking in late March. Euura exiguae is the commonest sawfly in California and is extremely abundant locally on river sandbars and banks. The species of Euura on S exigua in the Great Basin is probably the same as E. exiguae, but its ocellar basin is often similar to E. lemmoniae, and the sheath is rougher in outline than that of individuals from cismontane California.

Euura exiguae
Stem sawfly
[Page 214]

This sawfly induces linear, gradually tapering, integral stem galls on narrowleaf willow (Salix exigua) and dusky willow (Salix melanopsis) and possibly other related species.