Euura S. gemma Walsh.

"On Salix humilis. The lateral bud of a twig enlarged so as to be twice or thrice as long, wide and thick as the natural bud before it begins to expand in the spring ; its external surface otherwise entirely unchanged both in texture and colour. Internally, instead of the normal downy embryo leaves, it contains early in the autumn a homogeneous grass-green fleshy matter, which is afterwards gradually consumed by the larva, leaving nothing at last but a mere shell partly filled with excrement. The gall is monothalamous, sometimes one only on a twig, some- times two or three or more at irregular intervals, very rarely as many as three or four formed out of three or four consecutive buds.

Length .17 to .36 inch
Breadth .10 to .17 inch. "— Walsh.

The anatomy of this gall presents little differentiation of tissue. A cross section shows that the entire mass of the gall consists of small thin-walled cells, shown in Fig. 68. The bud scales surrounding this group of cells resemble those of the normal bud except that the cuticle of the epidermis is abnormally thickened.

Euura orbitalis

Lateral, monothalamous twig enlargements 4 to 9 mm long, 3 to 4 mm wide

Euura salicis gemma, n. sp.

On Salix humilis

The lateral bud of a twig, enlarged so as to be twice or thrice as long wide and thick as the natural bud before it begins to expand in the spring, its external surface otherwise en- tirely unchanged both in texture and color. Internally, instead of the normal downy embryo leaves, it contains early in the autumn a homogeneous, grass- green, fleshy matter, which is afterwards gradually consumed by the larva, leaving nothing at last but a mere shell, as thin as paper, and partly filled with excrement. Sometimes, from the egg failing to hatch out, this green fleshy matter remains unaltered till the spring. The gall is monothalamous, sometimes one only on a twig, sometimes two or three or more at irregular intervals, very rarely as many as 3 or 4 formed out of 3 or 4 consecutive buds. Common and not local. Described from 34 specimens. Length .17 — .36 inch; breadth .10 — .17 inch. Analogous to the Cecidomyidous gall 8. cornu Walsh, but very differ- ent in its general aj^earance and in its internal structure.

Euura gemma

Salix
Bud galls

Enlarged lateral bud, sawfly

Euura gemma

Host: Salix humilis

In this species, the gall is formed by the abnormal swelling of a lateral bud.

Range: Toronto Ontario

Euura salicisgemma

Valid name. — Euura orbitalis Norton 1862 (= Euura salicisgemma Walsh, synonymized by Norton 1867).

Host. — According to Walsh (1866b: 248, 250), this species creates bud galls on Salix humilis Marsh.

Notes. — We studied specimens from Canada (Quebec and Ontario) and U.S.A. (Illinois, Missouri, New Hampshire, and New York).