[Synonymized as Andricus palustris]

Dryocosmus quercuspalustris (Osten Sacken)

Cynips (Trigonaspis?) quercus palustris
Andricus (Callirhytis) palustris
Dryophanta liberaecellulae

Produce leaf galls on red oaks.

Mass, Ont to FL, west to Iowa, La.

New Observations on the Gall of CYNIPS QUERCUS PALUSTRIS, 0. S.

Among the oak galls described in my previous articles, one of the most singular is the gall I named Cynips quercus palustris, from its frequent occurrence on Q. palustris, the pin-oak, although it is also occasionally found on other oaks of the red-oak group. This gall is especially remarkable on account of a small, cocoon-like body, containing the pupa, which rolls freely about in a comparatively large cavity, without being connected in any way with the walls of this cavity, or, in other words, with the substance of the plant upon which the gall is growing. An examination of the shell of this cocoon-like body (which, for brevity's sake, I will call ovule) proves that it does not consist of animal, but of vegetable matter, in other words, that the ovule is not a cocoon, although it contains the larva and afterwards the pupa. The growth of these galls is so sudden that, although I have seen thousands of them, I do not remember having seen one which was not full grown as far as the size is concerned. Once or twice only I discovered specimens arrested in their growth by some unknown agency and withered in that state; and in such specimens I observed the ovule still connected, by a short stem, with the leaf or branch upon which the gall was growing. It would seem, therefore, that the ovule is nothing but the usual kernel, existing in many other galls, but which here, during the growth of the gall, becomes disconnected from its shell.

During my rambles in the Central Park, in New York, in May, 1869, among numberless galls of this kind on the pin-oak, I observed a good many which were double, that is, consisted of two galls soldered together. Such galls instead of globular were oblong, sometimes slightly narrowed in the middle. Usually, there was no partition on the inside between the two galls ; in the cavity thus formed was the likewise double ovule. The coarctation in the middle of the ovule was generally much more marked, than that of the gall. The double ovule contained two well-formed pupae without any partition between them, and hence almost in contact with each other.

Such double galls showed different degrees of coalescence, and the coalescence of their ovules was always in exact proportion to the coalescence of the outer shells of the galls. Sometimes the galls, although coalescent externally, were still separated by a partition internally; then each gall contained its own ovule. But whenever there was no inner wall between the galls, the ovules were also coalescent. In one case I observed the inner wall only partially removed, the cavities communicating by a rather small opening ; the ovules were in this case coalescent by a small portion of their surface, otherwise retaining their rounded shape and thus almost representing the figure eight.

In one of the galls I observed a small green caterpillar with yellow stripes, which had taken its abode in it and eaten up a part of the ovule, and perhaps also sucked out the larva.

Dryocosmus palustris (Ashm.)

Quercus coccinea, falcata, ilicifolia, imbricaria, marilandica, nigra, palustris, rubra, texana [buckleyi], velutina
Leaf galls, integral
Globular, 10-17 mm in dia., with a free-rolling cell, wall 1 mm thick, appearing with the leaves in very early spring.

[Photo caption]
On Q. velutina. On all the red oaks. In Chicago emergence varied from year to year; May 31, 1906, June 19, 1907, May 28, 1908, June 12, 1909. Kinsey liberated adults on a small tree covered with a net in a greenhouse and females oviposited on under side of the leaves. In Sept. galls which he determined as those of Zopheroteras compressum (Gill.) were found.

Diplolepis palustris

Galls were collected at Evanston. Winnetka, Ravinia, and Willow Springs, IL.; Miller, Ind.; Onekama (T. Hatfield), Mich.: Cedar Rapids (J. H. Scott), Iowa; East Hampton (C. R. Crosby), N. Y, ; Plummor Island and Chesapeake Beach. Md.; Falls Church. Alexandria, Rosslyn, and at Apple Orchard Camp in Bedford County, Va.

The young galls appear with the leaves in the spring being as large as a pea when the leaves are an inch and a half long. Seventeen days later adults were emerging. In the Chicago area the following emergence records indicate the variation from season to season: May 31, 1906, June 19, 1907, May 28, 1908, June 12, 1909, May 26, 1911. The galls sometimes occur on the axis of the staminate flowers.

Brodie collected galls on red oak at Toronto, Canada, where adults emerged July 2-10, 1888 and June 6-9, 1889.

Andricus palustris

Cynips quercus palustris
Cynips quercus notha
Andricus palustris
Andricus notha
Callirhytis notha
Callirhytis palustris
Dryophanta notha
Dryophanta palustris
Andricus pusulatoides
Neuroterus notha
Callirhytis pustulatoides
Callirhytis quercus-palustris
Callirhytis quercus-notha
Callirhytis pusulatoides
Cynips notha
Cynips quercus aquaticae
Spathegaster quercus laurifoliae
Andricus quercifoliae
Dryophanta liberaecellulae

Galls. — Globular, entirely hollow, succulent galls (Figs. 23 and 24) the size of a cherry, containing a free larval cell. The galls average about 3-12 mm. in diameter, are green or rose-tinged, very succulent, quickly shrivelling or decaying, and are entirely glabrous or in other instances roughened or densely but finely pubescent, depending upon the nature of the host. The mature gall is thin-walled, entirely hollow, more or less filled wuth a liquid, and contains a single larval cell, whitish, averaging 2.0 mm. in diameter, hard but thin- walled, entirely free, rolling about within the gall. Singly or in clusters, sometimes somewhat fused together, on the young buds, aments, petioles, and leaf-blades of oaks, sometimes only slightly attached, at other times inseparable from the leaf-tissue. On Quercus coccinea , Q. falcata, Q. ilicifolia, Q. imbricaria, Q. marilandica, Q. palustris, Q. phellos, Q. rubra , Q. velutina, and most likely other red oaks.

Range: Ontario, MA, ME, RI, CT, NY, NJ, PA, DC

I have examined the types of Andricus notha (Osten Sacken) and the adults appear to be true palustris. The galls are somewhat more oval in shape, with the larval cell more elongate, but I have found that that character shows gradations in large series of palustris and there is little doubt that notha is, as Osten Sacken strongly suspicioned, not distinct. Beutenmuller makes Andricus pusulatoides Bassett a synonym of notha. Beutenmuller (1911, Bull. Amer. Mus. Nat. Hist., XXX) also says that he cannot find essential differences between true palustris and the types of Dryophanta aquaticae, D. laurifolice, and D. liberaecellulae but, because of lack of sufficient material, he prefers to consider them distinct. I can hardly see any justification for keeping those names out of the synonymy.

The gall of Andricus palustris palustris is one of the best-known of the galls of early spring, appearing abundantly on red oaks of many species, often before any leaves have appeared. They often crowd closely on the flowers of the oaks. When the galls first appear they are solid, with the larval cell distinct but entirely connected with the outer walls of the gall; but within a very few days or even hours the gall, growing very rapidly, becomes hollow, leaving the larval cell (which had gained its full size in the young gall) loose to roll about within the enlarged outer wall at every movement of the branches of the tree. How the nourishment is provided for the larval cell and the enclosed larva is a process yet to be studied. During damp weather the galls will be found to contain a more or less viscous liquid, and placed in a pan of water they become filled with this liquid. It is probable that food is carried by osmosis to the larval chamber. Galls taken from the tree will grow still larger if placed directly on very moist sand or in water indicating how independent an organism these deformations may become.

Because the galls are so very succulent they should not be gathered for breeding until they are about mature, and should then be placed directly on very moist sand. The growth of these galls is very rapid after their first appearance upon the trees and they are mature within ten days or two weeks. The pupation period of the insect is very short; within a few days the adult emerges and within another few days the galls are mostly completely withered away or have decayed.

The adults emerge from mid-May to June 4, depending on the latitude and the progress of the season. The insects are produced in about equal numbers of the sexes. They copulate almost immediately upon emergence and run rapidly up the branches to the young leaves, on the under sides of which they settle to oviposit, often remaining there for several days before they die. In all, only about a month has passed from the time of the first appearance of the young gall to the time of oviposition. Over ten months will be required for the alternate generation to reach full maturity.

The experiments by which I was fortunate enough to discover the relations of the two generations of this species were made under the strictly controlled conditions which I have described in the introduction. The tree on which the sexual adults were put was covered with a net for almost a month and there was no chance of other insects having reached it during that time, nor is there much likelihood of the galls having been produced by insects from any other source. Of the thirty small oaks in the greenhouse, none produced any galls that season (1918) except the one on which the palustris had been isolated. Several scores of the adults of that form were observed to oviposit on the under surface of the leaves on which eight galls of Philonix compressa were found the first of September. The small size of the galls had prevented their detection earlier, for it is likely that they appear by the first of August.

P. compressa was a '‘species’' known definitely from only two stations, Westchester Co., N. Y., and Ames, Iowa, while palustris had been known for sixty years to be a very abundant species throughout eastern America. It was rather surprising to find an apparently rare, local species to be the alternate form of one of the commonest of widely distributed galls. Fortunately, I recalled definitely the location of the very trees on which I had found the palustris galls from which the experimental material had been bred. I made a trip to these trees and found the leaves bearing an abundance of the compressa galls. Then I found the galls in the Millett Thompson Collection, taken in Massachusetts or lthode Island; these were figured in the Thompson Catalogue but the collection was not recorded in the text. After that, I collected compressa galls at Melrose Highlands, Forest Hills, and Blue Hills, which are in the neighborhood of Boston, and always found it abundant at that date. The small size of the galls and the fact that they are very quickly deciduous is sufficient explanation of the failure of previous collectors to find the form.

Dryophanta liberaecellulae n. sp.

Quercus rubra and coccinea

Gall.--Globular excrescences on the leaves of the red and scarlet oaks, sometimes taking into themselves the entire leaf tissue and at others surrounded by the blade of the leaf as is the case of Amphibolips nubilipennis or Andricus singularis, either of which it very much resembles, but from which it differs by having a somewhat roughened and fuzzy exterior and a much thicker outer wall, and by having the larval cell perfectly free to roll about within. The galls vary from 6.5 mm to 9.5 mm in diameter.

When gathering the galls on May 20, 1889, it was noticed that some of the flies had already escaped, and on May 28th occasional galls could be found with the flies still in them.