Cynips quercus tuber [contains the first description of the anatomy of the true inducer]

Nine specimens.

I have a single male gall fly reared from the same galls, but it differs so much from the female that I am inclined to think it belongs to a different species.

Though the galls are very much alike, the venation of the wings, the pleurae, and several other points of difference mark it as a distinct species from C q. similis. Dr. Fitch has figured the gall of his C. q. tuber which he found "quite common particularly upon the soft and tender limbs of young (white oak) trees" (N. Y. Rep., Vol. 2d, No. 309). He describes (1. c. No. 310) the galls of C. q. arbos as "swellings similar to that above described, growing on the tips of the limbs of aged and large white oak trees."

My galls, which are probably identical with his C. q. tuber, were gathered from low, shrubby white oak bushes, though I have often Been precisely similar ones on large trees. Dr. Fitch's descriptions of the flies from C. q. tuber or C. q. arbos will apply, so far as they go, to either the gall flies, or to the guest flies as the inquilinae are termed by Mr. Walsh. For the reasons that follow, I am led to think that the species he described under the above names are both inquilinious species.

1st. My galls were gathered about the 20th of June, and were then green and soft like the wood of the young shoots on which they grew. The insects were then in the pupa state, and the imago came out early in July. The gall from which Dr. Fitch's C. q. arbos was reared was found in March, and were of the preceding year's growth, as were also those of C. q. tuber, if we may judge from his description of the color of the gall, which will only apply to the galls long after the true gall- flies have left them.

2nd. My galls gathered from young white oaks, and which answer perfectly to his figure and description of C. q. tuber, produced females with 13-jointed antenna?, while his have but 12 antennal joints.

3rd. I have gathered several hundreds of these galls in the autumn, winter and early spring within the last two or three years, but have never reared from them one true gall-fly, though they have produced large numbers of male and female guest-flies — the male answering perfectly to Dr. Fitch's description of C. q. arbos. The female he had not seen.

4th. The galls I collected in June have not yet produced any guest- flies, but cutting open several to-day I found in one a large living larva — the others were empty or contained dead gall-flies that had not been able to eat their way out of the dried gall. From the above facts I am forced to believe that the galls C. q. tuber and arbos Fitch are both produced by the same fly, and that it is the same species that I have described above and for which I retain Dr. Fitch's name, C. q. tuber. Dr. Fitch has, no doubt, described two distinct flies, for Mr. Walsh, who has devoted much attention to the guest-flies of the oak galls, finds that not only do some species live in several different species of galls, but that the same kind of gall may produce more than one species of guest-fly. (Proc. Ent. Soc. Philad. Vol. 2d, p. 465.)

Mr. Walsh, in the article referred to, mentions other of Dr. Fitch's , species which he is satisfied are inquilinae, and not the producers of the galls from which they were reared. (See pp. 464-5, 484 and 494.) His remark that "C. q. tuber Fitch is in all probability a guest-fly," escaped my notice till this moment.

Callirhytis clavula

A hard, woody, club-shaped gall, which occurs on the tips of twigs of the white oak, Quercus alba. Leaves frequently grown from it.

Contains several larval chambers.

Colo: green, often tinged red, turning brown.

Callirhytis clavula

Cynips tuber
Cynips phellos
Cynips arbos

Terminal club

Andricus (Callirhytis) clavula

Cynips arbor
Cynips clavula
Andricus clavula

Forms a club-shaped gall at the tips of the twigs of the White Oak (Quercus alba). Early in summer it is green; in winter it is of the same color as the twig, and is very hard and woody. Very common.

Cynips CLAVULA Bassett in litt. (Syn. C.q. tuber Bassett, non Fitch). (Q. alba).

This insect, described by Mr. Bassett (Proc. etc. III. p. 685) as C. q. tuber Fitch, could not retain this name, as Mr. Bassett himself proves that it is not the insect described by Dr. Fitch, the latter being a guest-fly. I have therefore adopted the name C. clavula, suggested to me in a letter by Mr. Bassett himself. Although this insect has a pubescent thorax, like Cynips in the restricted sense of Hartig, I am not sure whether it is to be referred to this genus. According to this author's opinion (1. c.) this gall and that of C. q. arbos Fitch are produced by the same insect. Both C. q. tuber Fitch and C, q. arbos Fitch are guest-flies; compare below, the genus Ceroptres).

Ceroptres arbos Fitch
Syn Cynips quercus arbos

Ceroptres tuber Fitch
Syn Cynips quercus tuber

Mr. Bassett has shown (Proc. etc. Ill, p. 687) that both galls, de- scribed by Dr. Fitch under the above-mentioned names are produced by the same gall-fly, which was not known to Dr. Fitch, and that this gall-fly occurs only on soft, green shoots of the same year's growth, whereas the galls of the last year's growth, the only ones described by Dr. Fitch, always give guest-flies. These guest-flies, as I have had occasion to observe myself, belong to the genus Ceroptres. We can take it for certain, therefore, that Cynips q. arbos Fitch, the male of which is said to have 15-jointed antennae, is a Ceroptres. Whether C. q. tuber Fitch, belongs to the same genus, is somewhat doubtful, as it is said to have 14-(male) and 12-(female) jointed antennae. Whether this statement is based upon a mistake, or whether Ceroptres male sometimes has 14-jointed antennas (which would agree with Hartig's statement), or, finally, whether C. q tuber Fitch, belongs to some other inquilinous genus, I do not pretend to decide. The last hypothesis, however, seems to me the most improbable of all.

Callirhytis clavula

Oak club gall. Terminal, club-shaped, about 15 mm. in diameter with several leaves growing from it, containing one to three larval cells. Green while growing but becoming brown and woody after the escape of the adults in early July, the old galls persisting for years. On trees of Q. alba.

Callirhytis clavula

Quercus alba
Stem galls, woody stem swellings
Abrupt swelling at apex of the year's growth, bearing several leaves.

A terminal club like Callirhytis clavula

Quercus stellata
Stem galls, woody stem swellings
Never reared.

[Photo caption]
On Q alba. Oak Club Gall. Adults emerged July 9, 13, 15 (DC). A similar gall (never reared) occurs on Q stellata in Texas, MO, and on Long Island NY.

Callirhytis clavula, usually on white oak

Callirhytis clavula

The oak club gall on Quercus alha has been collected at Kenilworth, Winnetka, Glencoe, Ravinia, Fort Sheridan, Waukegan, La Grange, Willow Springs, Utica, and Moline, IL. ; Miller, Ind.; Onekama (T. Hatfield), Mich.; Syracuse and Farmingdale (Crosby), N. Y.; Popular Bluft', Mo.; Plummer Island, Md.; Washington, D. C; East Falls Church, Va., and Blue Hills, Mass. About Chicago pupae were found in the galls in various years on June 11, July 12, and July 16. One emerged July 12, 1912. At Washington living adults were cut out of galls on July 16, 1920 and in 1924 they emerged July 9, 13, and 14. Beutenmueller has had adults emerge at New York City July 14-30. Brodie collected galls at Toronto but seems not to have reared adults. Girault reared adults at Blacks- burg, Va., July 12, 1901.

What seems to be the same gall has been taken on Quercus stellata at Mineola, Tex.; Poplar Bluff, and Washington.

309. Cynips quercus-tuber, new species

On or near the ends of the small limbs and twigs of the white oak, hard irregular swellings thrice as thick as the twig below them, the bark upon them of a brighter cherry red color than elsewhere, and their substance internally corky and woody; produced by the stings of a small black gall-fly with dull pale yellow antennae, mouth and legs, its hind shanks and its antennae towards their tips being dusky, its length 0.08 and to the tips of its wings 0.13.

These tumors or galls are quite common, particularly upon the soft and tender limbs of small young trees. Two distinct varieties in their form will be observed as they grow at the ends of the limbs, or lower down upon their sides. Those upon or near the tips of the limbs are shorter rounded galls, little longer than broad, and usually of a deeper red color and a more irregular uneven surface. They are about a half inch in length and a fourth less in thickness. Those growing along the side of the stem are longer elliptic galls of about the same width as the preceding, but twice or three times as long, and of a paler though still a deep cherry red color. The whole circumference of the limb is involved in this diseased swelling, except a narrow stripe along its hind side where the bark retains its natural striated appearance. When fully grown the surface of both kinds of these galls becomes glaucous white, as though thinly coated with moldiness. Sometimes two, three or more of these tumors occur on the same limb, placed irregularly one below the other, or running partially into each other. A single one, however, always suffices to kill the limb at and above the point where it is situated, thus arresting its onward growth until one of the lateral shoots below grows to become a leading shoot in place of the one thus destroyed.

On cutting into these galls the small limb on which they grow is found to have its wood thickened or swollen, and over it, forming the chief bulk of the tumor, is a corky substance of a yellowish brown or snuff color, between which and the wood are several small hard grains resembling seeds, each having a cavity in its center, in which, doubled together, lies a soft white footless worm or maggot. This, on completing its growth, changes to a pupa in the same cell, and subsequently to a fly like its parent above described; whereupon, to escape from its confinement, it gnaws out of this hard seed-like envelope and onward through the corky substance and the external bark, thus producing those small perforations like pin-holes, which are always seen in these tumors after the insects have made their exit therefrom.

310. Cynips quercus-arbos, new species

Swellings similar to those above described, growing on the tips of the limbs of aged and large white oak trees; producing a small black gall-fly having all its legs and antenna of a bright pale yellow color, and one more joint in the latter organs than in the preceding species in the males, which sex is 0.06 in length, and to the tips of its wings 0.10.

I have in repeated instances observed these swellings at the tips of the lofty limbs of mature and aged oaks, when the trees were felled and their limbs thus brought within view. But having until this moment supposed these galls the same with the preceding species, I have taken no care to obtain the flies from them.

The fact has heretofore been stated that where trees are standing apart, for furnishing a shade in pastures and other cleared lands, or as ornamental trees in parks and pleasure-grounds, they gather more insects and are hence more stinted and deformed in their growth, than when they arc associated together in forests. A large solitary oak which formerly stood in prominent view from the door of my dwelling was noticed for many years as making no perceptible advance in height or in the size of its body and limbs, although apparently healthy and clothed luxuriantly each summer with foliage. One morning in March this tree was observed cut down, and on repairing to it, it was discovered that the extreme ends of all the more vigorous and thrifty limbs and twigs were swollen into knobs or galls, wherefrom these ends would perish and their onward growth be thus arrested, all the other more puny limbs showing on their ends dead and decaying knobs of the same kind, which had grown in preceding years, thus it was evidently this small gall-fly, which, by killing the ends of all the most vigorous and thrifty shoots, year after year, had been retarding the further growth of this majestic tree. The galls were at that time perforated with pin-holes, showing that the fly had come from them the preceding autumn. On a careful search, however, two were found with the insect still in them. These were placed in a glass jar, and a single male fly was obtained from them, which I now discover to be unlike the foregoing species. I hence infer this to infest mature and aged trees, whilst all my specimens of that were reared from the more accessible galls growing on the tender juicy branches of young shoots and saplings.

Callirhytis clavula Fitch

A superficial examination of the gall of Callirhytis clavula Fitch (Fig. 33 a. b. c. d.) shows no resemblance to the preceding galls except in location at the tip of the stem. The gall is apparently a mere enlargement of the tip of the stem, and containing one or more larval chambers. Examination of section under a compound microscope, however, reveals a condition similar to that described for C. solidaginis and C. s.-strobiloides. Each larval chamber is in reality the apex of a bud. The young leaves of the bud are closely applied to each other and their structure unaffected by the insect. As the gall developes the leaves do not unfold but assume a corky texture and in the fully mature gall their identity is almost lost.

Andricus clavula

Cynips arbor
Cynips clavula

Quercus alba

Twig-gall, being a club-shaped swelling of the extreme tip. 1.5 X 2-3 cm. Green, single-chambered, becoming woody and dark after emergence of insect in midsummer. Surface often corrugated and covered with cork spots. Cedar Point and Huron. Common.

Callirhytis clavula

Cynips quercus-tuber
Cynips clavula
Andricus clavula

Club-shaped woody gall at end of twigs. Sometimes leaves develop from the bud of which this gall is a malformation. Polythalamous, 2-4 cm. long. Green occasionally faintly marked with red, turning brown. Common on white oak, Quercus alba. Insects from April to July.

Andricus clavula Bass

The red swollen tips of the twigs of Quercus alba., which are the galls of the above named gall-fly, are very common in Michigan and Iowa. From these galls I have reared several specimens of the guest, Ceroptres petiolicola., but no true gall-flies.

Callirhytis clavula

Terminal or subterminal swellings of the limb
Monothalamous; of a hard, woody structure

Syn C arbos, C tuber (Q alba); Neuroterus phellos (Q phellos); C similis (Q ilicifolia); C aquaticae (Q aquatica [nigra])

Callirhytis clavula [Riley claims that Pergande found evidence that wasps identified as C clavula oviposited in leaves later bearing C quercusfutilis galls; Kinsey believed this was incorrect]

On April 20, 1894, my attention was called by Mr. Pergande to several specimens of Callirhytis clavula Osten Sacken ovipositing in the buds of Quercus prinus. This is a rather large, winged agamic form, which Mr. Ashmead informs me he has actually bred from the clavula gall. The same species also oviposits in the buds of Quercus alba. The flies were sitting on the buds with the head towards the tip of the bud, and were so absorbed in their work that they scarcely moved or altered their position, even when the twigs were allowed to sweep back with some force. The ovipositor was deeply inserted within the scale-like covering of the buds. On carefully removing the scaly covering of a bud that had been pricked, quite a number of eggs were found in clusters of three or four together, and a few singly, inserted in the tender, new, embryo leaves. It was further found that the eggs were inserted on both the upper and lower surfaces of the leaf and almost entirely hidden by the silvery pubescence of the newly formed leaf. They were attached by a short stout pedicel or stem which, however, upon very careful examination, was found to extend for a great length (six or seven times the length of the exposed egg-body) like a fine thread into the sub stance of the leaf. The distal or anterior end of the egg-stalk was also somewhat enlarged, looking like a bit of shrivelled skin. The exposed portion of the egg or egg-body was white, glistening, elongate-ovoid or bean-shaped in form and about .2 mm. in length. Two days later, or on the 22d, additional flies were observed ovipositing and the buds were marked. On the 27th these were examined and it was found that the pedicel had become shorter and stouter, while the anterior or buried end had greatly increased, the exposed portion being now half empty of its contents. Five days later, April 2yth, the young leaves had formed from these same marked buds and the eggs were still in position, but mostly empty, and when removed and closely examined it was found that under the epidermis and below the base of the exposed egg-shell there had formed a soft, colorless, globular body, having a yellowish streak internally. This body, probably the first larval stage, is easily detached from the leaf, but no movement could be discerned and the thread-like pedicel had separated from it and disappeared. So far, there is no trace of a gall or swelling to be seen, although the affected leaves appear more or less crumpled or distorted. May 4th the same leaves were again examined and the young galls had already formed, appearing as slight thicken ings of the leaf, but scarcely elevated or prominent. The spot where the egg had been inserted forms a minute depression or hollow in the leaf, with the colorless and shrivelled egg-shell still in position, the cavity thus formed being in an oblique direction to the surface of the leaf. The cell or cells in each gall are re moved from the egg-shells about twice the length of these last, but for which there would be little trace as to where the egg en tered ; they are ovoid or rounded, and each contains a perfect larva, semitransparent or colorless, with a brownish ventral spot. Most of the galls contain three to five cells. From now on, the formation of the gall is rapid, the substance of the young gall being very juicy and succulent and of a yellow ish color, its outer margin or edge being pale pinkish. On May nth the galls were nearly full grown and proved to be Callirhytis ftitilis O. S., but no flies were reared until the middle of June, and from this time until the last of the month flies in both sexes were continually bred. A number of interesting subsequent observations were made upon this interesting species, but have no especial bearing on this communication. I ought, however, to state that Mr. H. F. Bassett (Psyche, Vol. 5, pp. 235-8, Dec., 1889) has described what is, apparently, the same insect as Cal- lirhytis radicis, which he reared from a series of blister-like cavities in the bark of the root of Quercus alba, and identified with the fly which he had himself observed ovipositing in the buds of the same oak and producing the gall which gives forth Callirhytis futilis Osten Sacken. There is consequently some confusion as to the actual relations of this sexual generation, and either an error as to determination on the part of Mr. Bassett or else an erroneous record of rearing on the part of Mr. Ash- mead. I have adopted the former as the more probable. There is, however, a third explanation, which, if verified by future in vestigation, would prove to be another interesting discovery in connection with these oak gall-flies, viz., that the same species may indifferently produce a gall on the root or on the twig. When we remember how closely these two parts of the plant are related physiologically and how readily the one in most trees may be converted into the other, such a discovery should not sur prise us.

Cynips quercus arbos Fitch

Quercus alba

"Swellings similar to those of Cynips quercus tuber, growing on the tips of the limbs of aged and large white oak trees." - Fitch

Is it identical with the following gall? But according to Dr. Fitch, this gall differs from that of C. quercus tuber by occuring on old and large trees only, whereas my gall No. 25 is found on trees of different age and size.

[Unnamed]

Quercus alba

Club-shaped, woody swelling at the tip of the limbs.

In June these swellings are yet green; later in the season, they become brown, hard and woody; in autumn, the leaves emerging from their tip, break off and the swellings at the tip of the limbs are easily noticed.

They can be recognized immediately by their club-shaped form, the vestiges of the leaves (usually three), broken off from their tip and the flattened, uneven surface between these vestiges, with the round hole, through which the insect escaped, generally in the centre. If cut lengthways in two, an elongated cavity is found just below this hole, and under this, a second, smaller, more rounded cavity. The latter contains the larva.

Sometimes there are two cavities of the latter kind and consequently two larvae occur in the same gall. On the 4th of July I found a pupa in an advanced state of ripeness in one of these galls; in the adjoining cell however was still a larva. I did not succeed in obtaining the gall-fly; instead of it, one of the specimens gave me Hydnocera verticalis Say, a col- eopteron, living, as it seems, parasitically on oak-galls, as I obtained it also from the oak-bullet gall (C. quercus tuber) of Dr. Fitch.

This gall is very common around Washington. Is it the gall of Gynips quercus arbos Fitch (Reports, Vol. II, No. 310)? From the gall of C. quercus tuber Fitch it is easily distinguished by its more constant form, its more uniformly woody consistency and the absence of the seed-like shells, containing the larva. I have found similar swellings on other kinds of oaks also.

Cynips quercus tuber Fitch

Quercus alba

Swelling of the small limbs or twigs

These galls are easily distinguished from the club-shaped galls by their inside. "On cutting into these galls, says Dr. Fitch, the small limb on which they grow is found to have its wood thickened or swollen, and over it, forming the chief bulk of the tumor, is a corky substance of a yellowish-brown or snuff" color, between which and the wood are several small hard grains, resembling seeds, each having a cavity in its centre," etc.

The flies which I obtained from these galls agree with Dr. Fitch's description, except that the neuration of their wings shows that they do not belong to the true gall-flies (Psenides) of Hartig. The second segment of the abdomen is shorter than the third, the radial area is closed by the prolongation of the subcostal vein along the anterior margin and the areolet corresponds more to the middle than to the base of the radial area, all characters distinguishing them from the true gall-flies. Still, I am at a loss to say to what genus they belong. I thought for some time that they agreed with Amblynotus Hartig, as defined in Reinhardt's recent Monograph of the Figitidse (Berl. Entom. Zeitschr. 1860), but the antennae of the male, which I examined repeatedly on the living and the dead insect, appeared to me 15- and not 14-jointed. The male of Dr. Fitch's C. quercus tuber has 14-jointed antennae. My 9 , like Dr. Fitch's, have 12-jointed antennae, if the last, very elongated joint, is counted for one. The female of Amblynotus, according to Reinhardt, has 13 joints.

Andricus (Sub-gen. Callirhytis) clavula

The galls are club-shaped enlargements of the ends of the twigs of Quercus alba. Flies emerge in July. Common east and west.