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PSYCHE.ORGAN OF THE CAMBRIDGE ENTOMOLOGICAL CLUB

EDITED BY GEORGE DININIOCK ND B. PICKtlIAN II:&NN.

Vol. II.-] Cambridge, Mass., January, 1879. [No. 57.

The Nervous System of Phylloxera.While engaged in studies on the anatomy of the Coccide 1

llhere were not at my command, specimens of the grape-vinepest--Phylloxera vastatrix Planch., so that, very naturally, myfirst concern, on returning from Europe in the smnmer of1876, was to submit the grape-vine louse to a hasty scrutiny,principally with the view of ascertaining whether it agreedwith 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 pecaliarities strikingly dif-ferent from those already described at length for Aspidiotus,there seemed no reasonable grounds for publishing the resultsof my short studies. Although some other points in the anat-

omy of Phylloxera seemed to me of interest, I hesitated to

make any amouncement of thegn, thinking that the greatamount of attention recently bestowed upon these insects hadprobably, at that time, already led to a very thorough acquaint-ance with their anatomy. Being at the time without access tothe literature on Phylloxera, it therefore seemed best to deferany 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 iom the

ihrther study of the plant-lice. But for an inquiry from Mr. J.Duncan Putnam, of Davenport, Iowa, it is likely I should not

have ventured to offer anything on this subject to the readersof PSYCHE. Late in January 1878, Mr. Putnam wrote to me"

Mark: Beitrgge zur Anatomie und Histologie der PflanzenIguse, insbesondere der

Cocciden in Archiv fiir mikroskopische Anatomie, Bd. 13 S. 31-86, Taf. 4-,6.

202

" Riley in his 8th Report, page 159, has described similartracheae 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 tome that it is not only not quite accurate for that insect, butalso that it hard].y corresponds to the nervous system of anyanimal.

Although I have not studied the sexual individuals-which are the ones described by Prof. Riley,--I have not theleast doubt that the objects very carefully drawn by him as

nerves are nothing other than the tracheae, as suspected byMr. 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 systen asobserved in the sexless individuals.

Fig. 9- Phylloxera vastarix Planch.--radicicol, winged.

An oblique view of the upper left surfce of the central portion of the nervous

system, as seen after cutting away the dorsal wall of the body, and the oesophaguswhere 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 figurerepresents the ganglia in a pupa of a winged form in which thetip of the wing-pads reached backward to near the middle ofthe abdomen.

Seventh annual repor on the noxious, beneficial md other insects of the state of

Missouri,... 1875, p. 99, fig. 19 and foot note.Eighth nnual report on the noxious, beneficisd and other insects of the state of

Missouri 1876, p. 158, fig. 48 5 and p. 159.Trans. S’. Louis Acad. Sci., v. 3, p. 283, fig. 22; p. 284.

That which first strikes one’s attention, in dissecting out thenerwus system, is the absence of" so marked a consolidation of’the ventral chain of ganglia as characterizes most of that groupof insects. Instead of the single oval ganglionic mass, whichin the near relatives of Phylloxera represents the concentratedventral chain of’ ganglia found in most arthropods, the Phyl-loxera presents two distinct ganglionic masses below the frontend 0[7 the digestive canal; or, to be more exact, two ptirsof’ ganglionic enlargemets. Tlie component lateral halves of’each of’ the two masses are so consolidated as to leave onlyslight external indication of’ the fusion. This fusion of’ thelat,eral halves is, lowever, like the antero-posterior consolida-tion, not so pronounced as in many of the plant-lice. Thesetwo nervous masses are joined to each other by a pair of’ stoutshort, longitudinal commissures. The anterior, in turn, is

joined to the superoesophageal pair of’ nerve-centres by a pairof much longer and more slender commissures.The posterior ganglionic pair is larger than either of the two

remaining pairs. It is continuous behind with a single mediannerve trunk, which promptly bifurcates. As seen from above itpresents a somewhat elongated heart-shaped, symmetrical out-line, its greatest breadth being considerably in front of itscentre. In a lateral view it is also seen to present the great-est thickness a little in advance of its centre. Its outline fromthe latter point of’ view is however, not quite symmetrical, thedorsal surf’ace being considerably more flattened than the ven-

tral. In their backward continuation, moreover, the dorsal andventral outlines are quite unlike, inasmuch as the Former passeswith almost unnoticeable curvature into the dorsal outline ofthe 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. At itsanterior end also, differences in the course of the dorsal andventral outlines are noticeable. While the outline of’ the dorsal,in passing by means of the stout commissure into that of thefirst suboesophageal ganglion, presents only a very gentle

Owing to the obliquonoss of the view furnishod by the figure this difference is notthere made prominent.

curve, the ventral outline is very sharply curved, or may evenform a cusp, thus reducing the ventral surf’ace of the com-

missure to a minimum.Both dorsal and ventral surfaces of" this ganglion present

longitudinal, shallow depressions, more conspicuous at the an-

terior than at the posterior end, and less pronounced above thanbelow. Further traces of the real nature of this doubleganglion are sometimes observed in the belavior of" the mainnerve-trunk which arises from its posterior end, inasmuch as

this trunk may be reduced to zero by an early division into itslaleral halves. Thus the notch at the anterior end becomescontinuous with the dorsal and ventral furrows, and, throughthegn, with the posterior notch which separates these two nervestems. In this manner the consolidation of the lateral halvesof the ganglion often appears far tiom complete. The lateraloutlines of this ganglion pass, by a gentle curve, into tlose ofthe main nerve. The latter sooner or later bithreates, the twobranches diverge and undergo further sub-division, in theireourse backward, to be distributed to the organs of the posteriorpart of’ the abdomen. In addition to this nain trunk therearise from the lateral margins of the posterior ganglion othernerves, which are not always symmetrically placed. As manyas fi)ur such nerves, at least, nay arise frown each side of thisganglion. The eomnissures between this and the first sub-oesophageal ganglion are short, rounded cords, which are

slightly flattened side-wise, and lie somewhat nearer the dorsalthan the ventral surfaces of the ganglia which they connect.Their narrowest measurements .indicate a thickness of aboutone-half or one-third that of the ganglion just described, and a

breadth of one-fburth that of the same ganglion. As seen fromabove, the opening embraced by the eommissures and the gang-lia which they join is an oval with its antero-posterior diameterequal to the breadth of one of the eonmissures, and its trans-verse diameter about half as long.The 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 notvarying much from three-fourths of the same. The longitud-

205

inal axes of the two suboesophageal ganglia do not form a

continuous line, but are so directed as to ibrm a very obtuseangle opening downward, as nay be seen in the figure. Thisdeflection in the nervous axis helps to increase the differencesalready noticed in the dorsal and ventral outlines connectingthe ganglia. This ganglion also presents both anterior and pos-terior indentations, as well as slight longitudinal depressions inits dorsal and ventral surfaces, indicative of its origin fi’omlateral halves. It is under the anterior end of this ganglionthat the two duets of the salivary glands unite and eventuallyopen into the beginning of the oesophagus. (See figure.)The circumoesophageal commissures are comparatively, lonc,

and slender. Their direction from the lower anterior aspect ofthe first suboesophageal ganglion isunlike that of’ most

arthropods obliquely downward and fbrward. In their course

they pass beneath a chitinous frame-work, md ultimately di-

verge to reach the infero-posterior surface of the two halves ofthe brain ganglion.The ganglionic pair which constitutes the superoesoplageal 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 halvesare joined by a brain-commissure of considerable length andof not much greater thickness than that of the circumoesoph-ageal commissures. Although my obsergations 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. Somuch, at least, is certain, that the figure here presented was

made f?om one of the winged insects, and that all my drawingsof the wingless forms show a much closer approximation of’ thetwo halves.

It can be in no way a source of surprise that the brain-mass,in the wingless form, is, noreover, considerably smaller thanin the winged form, when one reflects on the greater develop-

The anterior portion, or cross-piece, of this frame work is what have called arcus

superior, and the lateral portions costae superiores, in the paper above referred to.

Much as in Aspidiotus nerii. Vide op. cit., Taf. VI, fig. 81, gp.

:206

ment of" the organs of" special sense in the latter form. Thedistribution of tle nerves to the special sense-organs, however,has not been followed out, save that, in some of’ my sketchesof the wingless forms, I find a pair of nerves given off from theanterior end of the hemispheres, which I have no doubt sup-plies the eyes, and that another pair arises fi’om the ventralaspect of the same hemispheres, and probably makes its way tothe antennae. In the winged fi)rms, the hemispheres lie insuch 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 superiorbelind, and by the brain commissure in front. E. L. Marlc.

Cambridge, Dee. 2, 1878.

NOTn. After the preceding article was in type my atten-tion was directed to an article by Targioni-Tozzetti through a

review of tile same by P. Mayer in Hofinann u. Schwalbe’sJalresberichte ueber (lie Fortschritte der Anatomie und Physi-()logie. Bd. 6, Abth. 2" Entwickelungsgeschichte; Anatomieder wirbellosen Thiere. p. 185. 1875.

Inasmuch as the article alluded to contains a short statementwith regard to the nervous system in a nearly related species oftle same genus, [ will take advantage of the opportunity hereafforded 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 partsthe superoesophageal ganglion so as to define it with accuracy.Of the two ganglia beneath the oesophagus, the anterior is thesmaller, it is heart-shaped and joined by means of two thickand slort divaricating commissures to the posterior ganglion,vhich is larger and pyriform. The latter gives rise to lateralnerves, and ends with a long, thick cord, which, having fur-nished some branches in its course, is divided into otherbranches and there terminates.

Sommtrio di nuoYe osservazioni sullt Fillossera del Leccio e dellt Qucrce.--(Phyl-loxeraflorentina Ph. signoreti) Targ. Bull. Soc. Ent. Italiana., v. 9, p. 236-239. 1877.

207

]:t will be seen that, so far as the description goes, it corres-

ponds very closely with that which is given tbr Phylloxera vas-

tatrix. The extreme diculty of successful dissections withthese minute insects is sufficient explanation of the failure ofthe 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-intsting species, that the Malpighian vessels are absent;and finally to add that Targioni-Tozzetti has demonstrated thepresence of a pair of salivary glands in the Phylloxera whichhe has studied. J. Z. M.

Jan. 9, 1879.

BIBLIOGRAPHICAL RECORD.Contlnuedfrom page 200.

The date of pubiication here given in brackets ], murks the time ut which thework wus received by the Editor nless un eurlier date of publication is known to him.An asterisk before a title is the Rccorder’s certificate of accuracy of quotation. Cor-rections of errors und notices of omissions are solicited.- B.

os. 1059 to 1.135 are from Can. ritom., v. 8.* 1059. C: ,. S. BETI-IUNE. Annual address of the Presi-

dent of the Entomological Society of Ontario, 1875. p. 1-4.[Mar., 1876.]Progress of work; preparation for the Centennial Exhibition; meetings

of the Entom. Club A. A. A. S.; remarks upon Doryphora decemlineata,Pieris rapae and its prasite Pteromalas puparum, Caloptenus spretus,Leucania unipuncta, Clisiocampa americana, C. sylvatica, Bruchus pisi.

* 10(;0. L.F. [-Iaavu. New Texan m)ths, ). 5-7.[Mar., :1876.]Describes Parasa incisa, Euerythra, E. pha.+ma, Litodonta, L. hy<Iromeli,

Aletia hostia, Caradrina conviva, Mamestra brachiolum 2 n. gen., 6 n. spp.Catocala be’agiana Harv.--- C. jocaste Streck.

* 1061. G: J. B()WLS. Notes on Biston ursaria Walker.p. 7-9. [Mar., 1876.]

Describes the imagos, eggs, new-born larva and mature larva; abundancehabits; larva feeds on Populus and Prunus.

* 1062. G: M. D()DGE. New species of Acridini fromNebraska. p. 9-12. [Mar., 1876.]

Describes Pezotettix j,niu. P. autumnalis P. alba CaJoptenus lurida, C.regalis 5 n. spp., ntlvcs of Glencoe, Dodge Co., :Nebraska.

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