Eriophyes abnormis (Garman).

Chadwick's No. 144

Host Tilia americana L.

A very much lobed pouch-gall, usually on the upper side of the leaf, found rarely on the under side. The opening which is on the opposite side of the leaf to the pouch is surrounded by a dense growth of acicular trichomes.

The anatomical structure of this gall shows it to combine the characteristics of a pouch-gall with a type in which the epidermis lining the larval cavity is thrown into folds, as described in the case of the galls on Populus. The foldings of the lining of the gall cavity often coalesce, and practically divide the cavity into a number of compartments. Morphologically this is one of the most highly differentiated of our Phytoptocecidia. The lining epidermis has produced a large number of acicular, unicellular trichomes; these in some cases almost fill the cavities. The hairs surrounding the gall aperture are of the same type, as are also the normal hairs of the leaf. Glandular cells are much more abundant in the gall tissues than in those of the normal leaf.

Phytoptus abnormis

Phytoptus rotundus

Hosts: Tilia americana

Relationship: Irregular finger galls on both leaf surfaces

Range: KS, SD

Phytoptus abnormis, n. sp.

Produces galls on the leaves of the American linden or basswood, Tilia americana, Linn.

The transverse striae of the abdomen number about 56. This mite differs from all the other Phytopti I have seen in that the abdomen, just before the terminal sucker, is noticeably enlarged. But few specimens have been examined, as they have been very rare. In many of the galls, comparatively large, elongate eggs occur, which probably belong to some larger mite which preys on the gall-mites.

The gall is top-shaped, expanding above and contracting towards the upper surface of the leaves into a neck. It measures .155 inch in height, and .100 inch in diameter. The walls are deeply infolded, sometimes giving rise to unequal lobes. The outer surface is smooth, green and devoid of hairs. The cavity of the gall is made unsymmetrical by the deeper impressions of the wall. The inside of the latter is slightly roughened by small folds, and is clothed with long aciculate, unicellular hairs. These galls occur sparingly on the leaves of large trees in open woods at Bloomington, Illinois.