Nesmatus salicis desmodioides, n. sp.

On Salix humilis

A smooth, flattish, fleshy, sessile, yellowish-green, monothalamous gall of a semicircular outline, the chord of the semicircle adjoining the midrib of a leaf; its general shape like the seed of a Desmodium, or like the so-called "quarter" of an orange, the thin inside edge of the "quarter" closely hugging the midrib of the leaf, and the robust outer surface not biangulated but rounded off. No rosy cheek. The volume of the gall is generally about equally divided between the upper and lower sides of the leaf, but sometimes the lower portion is rather the larger. Usually there is but a single gall on a single leaf, but occasionally there are two of them either on the same side or on opposite sides of the midrib. One leaf was noticed with as many as three of these galls upon it. Length .23 — .50 inch; 131 specimens. The above is the appearance of the mature gall July 30; but on May 17 it is already nearly full-sized, and then many of them have a rosy cheek like the normal S.pomum. Abundant and not local. Distinct from S. pomum by its very different shape, and by its never having any rosy cheek when mature, and by the very distinct species of willow on which it occurs.

Pontania desmodioides Walsh.

"On Salix humilis. A smooth, flattish, fleshy, sessile, yellowish- green monothalamous gall of a semicircular outline, the chord of the semicircle adjoining the midrib of a leaf; its general shape like the seed of a Desmodium or like the so-called "quarter" of an orange, the thin inside edge of the "quarter" closely hugging the midrib of the leaf, and the robust outer surface not biangulated but rounded off. No rosy cheek. The volume of the gall is generally about equally divided between the upper and lower sides of the leaf but sometimes the lower portion is rather the larger. Usually there is but a single gall on a single leaf, but occasionally there are two of them, either on the same side or on opposite sides of the midrib." — Length .23 to .50 inch Walsh.

When mature this gall shows in cross section a cavity surrounded by a peripheral layer of little differentiated tissue. The epidermis has given rise to a very thick cuticle that is not present in the normal leaf. The bundle of the midrib has been injured only slightly by the ovipositor of the producer. The vascular strands given off from it almost encircle the gall along a line half way in from the epidermis.

A stage of the gall so young that the larva was unhatched shows the gall tissue to have been produced by cell division in the upper epidermis, the spongy parenchyma and the palisade parenchyma of the normal leaf (Fig. 80). At the thickest part of the gall, when it is in this stage, the upper epidermis has produced four layers of cells, the spongy and palisade parenchyma seven layers each. The lower epidermis has not divided as yet, and probably takes no part in the production of the gall. The abnormal cells from the palisade parenchyma show clearly their origin by their arrangement in rows at right angles to the surface of the leaf. The cells produced by the spongy parenchyma, on the other hand, are not regularly placed but include air spaces. The result is that the abnormal tissue in this case also resembles the normal tissue from which it is derived.

This stage of the gall shows that the cavity present in the mature gall has arisen between the tissue produced by the spongy and that derived from the palisade parenchyma of the normal leaf.

Nematus desmodioides

Weeping willow. Mass. Late June, Oval excrescence above and below leaf blade.

Pontania desmidoides

Nematus salicis-desmidoides
Nematus inquilinus
Pontania inquilinus

Leaf-gall, flattened bean-shaped, bisected by leaf, usually centered on a lateral vein, one to several galls on a leaf. 5-8 mm. long, 4-5 mm. broad and thick. Color various, usually crimson. Abundant in a restricted area. July 23.

Pontania desmodioides

Smooth, flattish, fleshy, sessile, yellowish green, on both surfaces of the leaf, length 6 to 12 mm, on S humilis.

Pontania desmodioides

Salix
Leaf galls

Flattish yellow-green, length .25 to .5 inch, sawfly, spring

Pontania desmodioides

Host Salix humilis

A smooth, flattish gall with a semicircular outline originating from the mesophyll of the leaf of the host. The last two galls mentioned are abundant in this locality. Especially in the western part of the city the numerous ridges and plains consist largely of sand sorted over and deposited by the wave action of the glacial. Lake Iroquois. In the light soil thus produced pines and oaks flourish and in the open spaces among these Salix humilis finds an ideal habitat. The resulting frequent occurrence of this food plant contributes to the abundance of several of our sawfly galls parasitic on this host.

Range: Toronto, Ontario

Pontania desmodioides

Nematus salicis desmodioides
Nematus inquilinus

Gall. — The gall is found on S. humilis. It is smooth, flattish, fleshy, sessile, yellowish green, monothalamous, semicircular in general shape like the seed of a Desmodium or the quarter of an orange. It is about equally divided between the two surfaces of the leaf; no rosy cheek. Generally there is but one gall on a leaf; one leaf was seen with three upon it. Length 0.23 to 0.50 inch. One hundred and thirty-one specimens. Gall mature July 30.

Galls probably belonging to this species have been received from the following localities: Lafayette, Ind., F. M. Webster, August 15, 1890, from which were obtained two parasites, Sympiesis sp. and Murytoma studiosa Say, supposed to be parasitic on Anthonomus sycophanta Walsh ; Eichfield Springs, N. Y., Th. Pergande, collector, September 28, 1886. Cadet, Mo., J. G. Barlow, collector, September 24, 1890.