Rabdophaga salicisrhodoides

Host: Salix humilis

Salix
Bud gall comprising many modified leaves
Leaves loose, exfoliate, forming an open rosette
Leaves almost as wide as long
Gall leaves more sessile, the gall longer than wide

[A drawing of this gall appears on page 277, Figure 410]

The gall simulates an elongated rose blossom. It is 1-2 cm in diameter and 2-5 cm long.

Range: IL

[Note referring to this and several other bud gallers]: Leaves of these galls are typically largest on the outside of the gall but narrow considerably toward the center of the gall. In this key only the outer leaf shape of the mature gall is described. The gall formers are always at the heart of the gall, surrounded by linear leaves. The larva feeds upside down and reverses position before pupation. The gall makers have one generation per year, are full grown in fall, overwinter in the gall in a cocoon, and pupate the following spring. Infested twigs are considerably stunted.

Rhabdophaga rhodoides

Large, loose, rosette gall, length 1 to 2 cm.

S rhodoides, n. sp.

On S. humilis

A monothalamous gall like an elongated rose, always growing singly on the tip of a twig, porrect, its general outline elongate-spherical, occasionally spherical and rarely short-spherical, .90 — 1.80 inch long and .70 — 1.90 inch in diameter, never with any twigs, however small, growing round it from the same stem. The leaves composing it are slightly pubescent, entire, with the midrib and branching side-veins very conspicuous, and are almost always opened out and with their tips recurved and occasionally at the extreme tip a little pinched together, but in a few cases they are loosely appressed except at the tip of the gall. The basal ones are small, the following ones larger, all sessile and heart-shaped with the basal lobes of the heart squarely truncate and the tip almost always taper-pointed in an angle of 70 — 80°; towards the tip the leaves become smaller and gradually more and more peduncled, till at the extreme tip the peduncle is generally twice as long as the leaf itself. Inside the gall the leaves suddenly become linear-lanceolate and gradually straighter as they approach the centre, till they finally embrace the lanceolate central cell precisely as in S. strobiloides. Sometimes the peduncled leaves at the tip protrude from the gall as the stamens and pistils of some flowers protrude from the corolla.

Described from 15 galls freshly gathered in November, and 50 — 70 gathered in July. Very common in Rock Island County, Illinois. This gall arrives at its full size by the middle of July, when the outside leaves are externally palish green, often changing towards the tip of the gall to pale yellowish green slightly tinged with ro.sy and externally more or less glaucous. In the autumn the leaves become pale greenish brown with a slight whitish pubescence externally, and, after hanging on the twig over a year, almost black.

Rhabdophaga rhodoides

Salix
Rosette galls, midge, early spring and summer

Open rosette gall. Willow cabbage gall