probably Cryptocampus nodus

Euura salicis-nodus
Cryptocampus salicis-nodus

Host: Salix sp.

Twig-gall, being a spindle-shaped enlargement of the herbaceous or young woody twigs, concentric with the stem as a rule, about 1 cm. in diameter, and ranging up to 3.5 cm. in length. Color that of normal twig.

Cryptocampus nodus

Euura salicis nodus
Cryptocampus salicis-nodus

A gradual enlargement of the twig, usually around the twig, and several near one another. Polythalamous. From twice to several times the diameter of the twig. 1-3 cm long. Larvae sometimes remain in gall over winter, sometimes go under ground. Emerge in April or May. On willow, Salix sp.

Euura nodus

Gradual enlargement of the twig, usually extending partly around it and several near each other, polythalamous, length 1 to 3 cm.

Euura salicis nodus, n. sp.

On S. longifolia [interior]

A mere gradual enlargement of a twig from 1/4 more than its norma] diameter up to twice its normal diameter, almost always without any abnormal roughness on the external bark, and always not confined to one side only of the twig. General color that of the twig. When cut into, Aug. 28, the interior of each gall is found to be pithy, and to contain 1 — 3 larvae in separate cells. Frequently, on a piece of a twig 6 inches long, 2, 3 or 4 of these galls are placed at irregular intervals. No appearance internally of any transverse plates or transverse fibres as in S. ovum and S. ovulum. Length .75 — 1.50 inch; diameter .10 — .2.5 inch. Described from 31 affected twigs. Abundant but very local. Very like the Cecidomyidous gall S. nodulus on the same willow, but is much larger, is polythalamous instead of monothalamous, and occurs near Rock Island, IL., in quite a different locality. Analogous willow-galls are made in Europe, not by a Euura, but by several small species of Nematus.

Euura nodus

Salix
Twig galls

Gradual twig swelling, length .5 to 1.5 inches, sawflies

Euura salicisnodus

Valid name. — Euura salicisnodus Walsh.

Host. — According to Walsh '"Salix longifolia.'' Its currently used name is either Salix interior Rowlee (= longifolia Muhlenberg) or Salix exigua ssp. interior (Rowlee) Cronquist (see Argus 1997). The galls are "a mere enlargement of the twig, polythalamous, pitchy inside, with its cells all internal" (Fig. 12).

Notes. — This species is probably related to E. atra Jurine, a species introduced from Europe together with its host plants Salix alba L. and S". fragilis L. and their hybrids. Euura salicisnodus is separated from E. atra by its extensive paler coloration and the galls which form an enlargement of the twig. Euura atra does not produce enlargements of the twig; its galls are practically unnoticeable. Examined specimens are from Illinois, New York, Michigan (?), Ohio, and Canada (London, Ontario). Two species described from the western United States, Euura macgillivrayi Rohwer and Euura exigua E. L. Smith, are associated with the same willow species (or very closely related ones) and they might prove to be only geographical forms of E. salicisnodus.