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Psyche 2:201-206, 1877.

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PSYCHE.
ORGAN OF THE CAMBRIDGE ENTOMOLOGICAL CLUB EDITED BY GEORGE DIMMOCK AND B. PICKMAN MANN. Vol. 11.1 Cambridge, Mass., January, 1879. [No. 57. The Nervous System of Phylloxera.
While engaged in studies on the anatomy of the Coccidae 1 there were not at my command specimens of the grape-vine pest -Phylloxera vastatrix Planch., so that, very naturally, my first concern, on returning from Europe in the summer of 1876, was to submit the grape-vine louse to a hasty scrutiny, principally with the view of ascertaining whether it agreed with other plant-lice in the possession of salivary glands. That question was soon settled in the affirmative, but, inas- much as the glands did not present peculiarities strikingly dif- ferent from those already described at length for Aspidiotus, there seemed no reasonable grounds for publishing the results of my short studies. Although some other points in the anat- omy of Phylloxera seemed to me of interest, I hesitated to make any announcenlent of them, thinking that the great amount of attention recently bestowed upon these insects had probably, at that time, already led to a very thorough acquaint- ance with their anatomy. Being at the time without access to the literature on Phylloxera, it therefore seemed best to defer any statement till such time as I might have the opportunity to learn what had already been written by others. Investigations of another sort have enticed me from the further study of the plant-lice. But for an inquiryfrom Mr. J. Duncan Putnam, of Davenport, Iowa, it is likely I should not liave ventured to offer anything on this subject to the readers of PSYCHE. Late in January 1878, Mr. Putnam wrote to me : 1 Mark: Beitrage zur Anatomie und Histologic der Pflanzenlause, insbesondere der Cocciden ; in Archiv fur mikroskopische Anatomie, Bd. 13, S. 31-86, Taf. 4-6.



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Riley in his 8th Report, page 159, has described similar tracheae in the Phylloxera as nerve chords. Is he right?" On turning to Prof. Riley's Reports I was not a little sur- prised at the description of the nervous system. It seems to me that it is not only not quite accurate for that insect, but also that it hardly corresponds to the nen70us system of any animal.
Although I have not studied the sexual individuals - which are the ones described by Prof. Riley,- I have not the least doubt that the objects very carefully drawn by him as nerves are nothing other than the tracheae, as suspected by Mr. Putnam. The nervous system will certainly be found to present other peculiarities than those figured by Prof. Riley, and probably will differ only slightly from the same system as observed in the sexless individuals.
Fig. 9 - Phylloxera vastatrix Planc1~- radicicola, winged. An oblique view of the upper left surface of the central portion of the nervous system, as seen after cutting away the dorsal wall of the body, and the oesophagus where it ascends from the level of the brain-commissure. Magnified about 100 diameters.
The following observations were all made on sexless root- infesting individuals in the month of August 1876. The cen-
tral portion of the nervous system, in both winged and wing- less forms, came under observation. The accompanying figure represents the ganglia in a pupa of a winged form in which the tip of the wing-pads reached backward to near the middle of the abdomen.
1 Seventh annual report on the noxious, beneficial and other insects of the state of Missouri, . . .
1875, p. 99, fig. 19, and foot note.
Eighth annual report on the noxious, beneficial and other insects of the state of
Missouri, . . .
1876, p. 158, fig. 48 5 and e ; p. 159.
Trans. St. Louis Acad. Sci., v. 3, p. 283, fig. 22; p. 284.



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That which first strikes one's attention, in dissecting out the nervous system, is the absence of so marked a consolidation of the ventral chain of ganglia as characterizes most of that group of insects. Instead of the single oval ganglionic mass, which in the near relatives of Phylloxera represents the concentrated ventral chain of ganglia found in most arthropods, the Phyl- loxera presents two distinct ganglionic masses below the front end of the digestive canal; or, to bs more exact, two pairs of ganglionic enlargements.
The component lateral halves of
each of the two masses are so consolidated as to leave only slight external indication of the fusion. This fusion of the lateral halves is, however, like the antero-posterior consolida- tion, not so pronounced as in many of the plant-lice. These two nervous masses are joined to each other by a pair of stout, short, longitudinal commissures. The anterior, in turn, is joined to the superoesopl~geal pair of nerve-centres by a pair of much longer and more slender comrnissures. The posterior ganglionic pair is larger than either of tlie two remaining pairs. It is continuous behind with a single median nerve trunk, which promptly bifurcates. As seen from above it presents a somewhat elongated heart-shaped, symmetrical out- line, its greatest breadth being considerably in front of its centre.
In a lateral view it is also seen to present the great- est thickness a little in advance of its centre. Its outline from
the latter point of view is, however, not quite symmetrical, the dorsal surface being considerably more flattened than the ven- tral. In their backward continuation, moreover, the dorsal and ventral outlines are quite unlike, inasmuch as the former passes with almost unnoticeable curvature into the dorsal outline of the main nerve-trunk, while the ventral outline suffers a con- spicuous and rather prompt bending to bring its course into a line parallel with the dorsal outline of the main nerve.l At its anterior end, also, differences in the course of the dorsal and ventral outlines are noticeable.
Wliile the outline of the dorsal,
in passing by means of the stout commissure into that of the first suboesophageal ganglion, presents only a very gentle 1 Owing to the obliqueness ~f the view furnished by the figure this difference is not there made prominent.




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curve, the ventral outline is very sharply curved, or niay even form a cusp, thus reducing the ventral surface of the coni- missure to a minimum.
Both dorsal and ventral surfaces of this ganglion present lonp$udinal, shallow depressions, more conspicuous at the an- terior than at the posterior end, and less pronounced above than below. Further traces of the real nature of this double ganglion are sometimes observed in the behavior of the main nerve-trunk which arises from its posterior end, inasmuch as this trunk may be reduced to zero by an early division into its lateral halves. Thus the notch at the anterior end becomes continuous with the dorsal and ventral furrows, and, tlirough them, with the posterior notch which separates these two nerve stems. In this manner the consolidation of the lateral halves of the ganglion often appears far from complete. Tlie lateral outlines of this ganglion pass, by a gentle curve, into those of the main nerve. Tlie latter sooner or later bifurcates, the two branches diverge and undergo further sub-division, in their course backward, to be distributed to tlie organs of the posterior part of the abdomen. In addition to this main trunk there arise from the lateral margins of the posterior ganglion other nerves, which are not always symmetrically placed. As many as four such nerves, at least, may arise from each side of this ganglion. The commissures between this and the first sub- oesophageal ganglion are short, rounded cords, which are slightly flattened side-wise, and lie somewhat nearer the dorsal than the ventral surfaces of the ganglia which they connect. Their narrowest measurements indicate a thickness of about one-half or one-third that of tlie ganglion just described, and a breadth of one-fourth that of the same ganglion. As seen from above, the opening embraced by the commissures and the gang- lia which they join is an oval with its antero-posterior diameter equal to the breadth of one of the commissures, and its trans- verse diameter about half as long.
Tlie first suboesophageal pair presents a flattened, rounded mass, in width one-third less than the posterior ganglion, and of a length equal to its own breadth, and a thickness not varying much from three-fourths of the same. The longitud-



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inal axes of the two suboesophageal ganglia do not form a continuous line, but are so directed as to form a very obtuse angle opening downward, as may be seen in the figure. This deflection in the nervous axis helps to increase the differences already noticed in the dorsal and ventral outlines connecting the ganglia. This ganglion also presents both anterior and pos- terior indentations, as well as slight longitudinal depressions in its dorsal and ventral surfaces, indicative of its origin from lateral halves. It is under the anterior end of this ganglion that the two ducts of the salivary glands unite and eventually open into the beginning of the oesophagus, (See figure.)
The circumoesophageal commissures are comparatively long and slender.
Their direction from the lower anterior aspect of the first suboesophageal ganglion is -unlike that of most arthropods -obliquely downward and forward. In their course they pass beneath a chitinous frame-work,l and ultimately di- verge to reach the infero-posterior surface of the two halves of the brain ganglion.
The ganglionic pair which constitutes the superoesopliageal or brain-mass presents considerable variations, from a rather in- timate union of the two halves2 to such a condition as is re- presented in the accompanying figure, where the lateral halves are joined by a brain-commissure of considerable length and of not much greater t,hicliness than that of the circurnoesoph- ageal commissures. Although my observations were not suf- ficiently extensive to exclude the possibility of an erroneous inference, I still think that these two forms of the brain-mass belong respectively to the wingless and winged individuals. So much, at least, is certain, that the figure here presented was made from one of the winged insects, and that all my drawings of the wingless forms show a much closer approximation of the two halves.
It can be in no way a source of surprise that the brain-mass, in the wingless form, is, moreover, considerably smaller than in the winged form, when one reflects on the greater develop- 1 The anterior portion, or cross-piece, of this frame work is what I have called arcus superior, and the lateral portions costae superiores, in the piper above referred to. 2 Much as iu Aspidiotus nerii. Vide op. clt., Taf. VI, fig. 31, gp.



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ment of the organs of special sense in the latter form. The
distribution of the nerves to the special sense-organs, however, has not been followed out, save that, in some of my sketches of the wingless forms, I find a pair of nerves given off from the anterior end of the hemispheres, which I have no doubt sup- plies the eyes, and that another pair arises from the ventral aspect of the same hemispheres, and probably makes its way to the antennae. In the winged forms, the hemispheres lie in such close approximation to these organs that the nerves will certainly be found to be very short.
As may be seen from the accompanying figure, the oesophagus ascends in the space bounded by the arcus superior behind, and by the brain commissure in front. 3. L. Mark. Cambridge, Dee. 24, 1878.
NOTE. - After the preceding article was in type my atten- tion was directed to an article by Targioni-Tozzetti 1 through a review of the same by P. Mayor in Hofmann u. Schwalbe's Jahre~be~icllte ueber die Fortscliritte der Anatomic und Physi- ologie. Bd. 6, Abtli, 2 : Entwickelungsgeschichte ; Anatomie der wirbellosen Thiere. p. 185. 1878.
Inasmuch as the article alluded to contains a short statement with regard to the nervous system in a nearly related species of the same genus, I will take advantage of the opportunity here afforded to give its substance.
The author says (1). 237) : &' The nervous system is com- posed, as far as regards the suboesophageal part, of two gang- lia ; it is not possible to separate from the surrounding parts the superoesophageal ganglion so as to define it with accuracy. Of the two ganglia beneath the oesophagus, the anterior is the smaller, it is heart-shaped and joined by means of two thick and short divaricating cornmissures to the posterior ganglion, which is larger and pyriforin. The latter gives rise to lateral nerves, and ends with a long, thick cord, which, having fur- nished some branches in its course, is divided into other branches and there terminates."
1 Sommario di move osservazioni sulla Fillossera del Leccio e della Querce.-(Pliyl- loxerajlorentina, Ph. signoreti) Tag.
Bull. Soc. Ent. Italiaiia, v. 9, p. 236-239. 1877.




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It will be seen that,, so far as the description goes, it corres- ponds very closely with that which is given for Phylloxera vas- tatrix. The extreme difficulty of successful dissections with these minute insects is sufficient explanation of the failure of the accomplished Italian to make out satisfactorily the super- oesophageal ganglion.
I will also avail myself of this opportunity to confirm for Ph. vastatrix the observation of Targioni-Tozzetti, made on an oak-infesting species, that the Malpighian vessels are absent; and finally to add that Targioni-Tozzetti has demonstrated the presence of a pair of salivary glands in the Phylloxera which he has studied. å£ L. M.
Jan. 9, 1879.
BIBLIOGRAPHICAL RECORD.
( Continued from page 200. )
The date of publication, here given in brackets [ 1, marks the time at which the
work was received by the Editor, unless an earlier date of publication is known to him. An asterisk * before a title is the Recorder's certificate of accuracy of quotation. Cor- rections of errors and notices of omissions are solicited. - B. PICKMAN MANN. Nos. 1059 to 1135 are from Can. Entom., v. 8. * 1059. C: J. S. BETHUNE. Annual address of th6 Presi- dent of the Entomological Society of Ontario, 1875. 11. 1-4.
[Mar., 1876.1
Progress of work ; preparation for the Centennial Exhibition ; meetings of the Entom. Club A. A. A. S.; remarks upon Dorypltora decemlineaia, Pieris rapae and its parasite Pteromdiis puparum, Caloptenus spretus, Leucania unipuncta, Clisioccmzpct a~nericana, C. syluaticu, Bruchus pX. * 1060. 1,. F. HARVEY. New Texan moths. 13. 5-7. [Mar., 3 876.1
Describes Parasa incisa, Euerythra, E. pliasma, Litodonta, L. hydromeli, Aletia hosiia, Caradrina conviva, Mamestra brachiolum = 2 n. sen., 6 n. spp. Catocala belfrqiana Harv. = C. jocaste Streck. * 1061. G: J. B~WLES. Notes on Biston ursaria Walker. p. 7-9. [Mar., 1876.1
Describes the imagos, eggs, new-born larva and mature larva; abundance habits; larva feeds on Populus and Prunus. * 1062. G: M. DODGE. New species of Acridini from Nebraska.' p. 9-12. [Mar., 1876.1
Describes Pezotettix jmius, P. autiimnalis, P. alba, Cioptenus luricic~, C. reqalis =: 5 n. spp., natives of Glencoc, Dodge Co., Nebraska.



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