Salicis brassicoides. n. sp. — On Salix longifolia [interior].

Monothalamous, sessile galls, expanding each 0.75 — 2.25 inch, and with the general outline of each spherical or oval, growing in a more or less close-set bunch of 1 — 11, like the sprouts of a cabbage-stump, on twigs which vary in diameter from .10 inch to .50 inch, sometimes from their tips but more generally from their sides, and often with several minute twigs growing from the midst of each bunch of galls, the largest galls generally on the largest twigs. The leaves composing each gall are all sessile, and are on the outside ovate lanceolate or lanceolate, and widely expanded and towards their tips recurved. Towards the tip of the gall they become smaller, slenderer, and gradually less expanded, and in the centre they are quite small, perfectly straight and linear-lanceolate, closely embracing the central cell containing the author of the gall. External leaves with the midrib, and generally some of the branching side-veins, pretty distinct. It is but very rarely that the leaves composing each gall show any traces of the peculiar, widely-removed serratures which characterize the leaves of the willow on which they occur, their edges being almost invariably perfectly entire. The color of the galls when recent, is the same as that of the recent leaves of the willow on which they grow, but at the fall of the leaf they become reddish brown, and after hanging on the twig more than one year, almost black.

Described from 19 bunches of galls. Very common near Rock Island, Illinois. The eggs that originate these galls must be laid from the middle of April to the end of May, and by the middle of July the galls have attained their full size. When the twig on which they grow is at all small, it generally dies the next spring.

- BD Walsh: (1864) On the Insects, Coleopterous, Hymenopterous & Dipterous: Inhabiting the Galls of Certain Species of Willow. Pt 1st--Diptera^©

Reference: https://www.biodiversitylibrary.org/item/23810#page/597/mode/1up