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PSYCHE.

THE SEGMENTATION OF THE INSECT HEAD.

BY JUSTUS WATSON I:rOLSOM, CAMBRIDGE, MASS.

The elucidation of the primitivesegments in arthropods is a most inter-esting and difficult morphologicalproblem. The rule of Savigny--emphasized by Huxley and others--that arthropods are fundamentally con-structed of successive rings, each ofwhich may bear but one pair of pri-mary appendages, although now un-doubted, has never been thoroughlysubstantiated when applied to thehexapod head. After )Tears of argu-ment, morphologists still disagree as tothe number of somites composing thehighly differentiated heads of insects,

Compare the latest text-books in respectto the subject. Kolbe (’9o) recognizesfive, as follows:. Ursegment Ftihler Augen, Oberlippe.2. Oberkiefer oder Mandibeln.3. Unterkiefer oder Maxillen.[4. Zunge oder Innenlippe.]5. Unterlippe.

Sharp (’95) says, "Morphologistsare not yet agreed as to their number,some thinking this is three while othersplace it as high as seven" three or fourbeing, perhaps, the figures at presentmost in favour, though Viallanes, whohas recently discussed the subject, con-siders six, the number suggested by

Huxley, as the most probable. Cho-lodkovsky is of a similar opinion."

Packard (’98) gives six:

Seg’rnent. Aflflendag’es, etc.

Ocellar (Protocerebral). Compound and simple eyes.Antennal(Deutocerebral). Antennae.

3. Premandibular, inter- Premandibular append-calary (Tritocerebral).,. Mandibular.

S. First Maxillary.6. Second Maxillary.

ages.Mandibles.First Maxillae.Second Maxillae, Lab-

ium. Post-gula, gula,submentum, hypopha-rynx, (lingua, ligula),paraglossae, spinneret.

Upon anatomical grounds, differentobservers have recognized from one toseven head segments. As mentionedby Packard (’98), Burmeister foundonly two Carus and Audouin three;MacLeay and Newman four; Straus-Durckheim seven. Huxley (’77) said,"It is hardly open to doubt that themandibles, the maxillae, and the labium,answer, to the mandibles and the twopairs of maxillae of the crustaceanmouth. In this case, one pair ofantennary organs found in the latter iswanting in insects, as in other air-breathing arthropods, and the existenceof the corresponding somite cannot beproved. But if it be supposed to bepresent, though without any appendage,and if the eyes be taken to represent

392 los YCHE. [August x$99.

the appendages of another somite, theinsect-head will contain six somites."

Huxley’s conclusions were the mostsatisfactory that could be derived froma study of the completed organs aloneand reduced the problem to these ques-tions- Do the eyes represent a somiteIs another antennal segment representedin insects? Do the labrum and hypo-pharynx represent distinct segments ?

Authors began to realize the impossi-bility of settling the problem uponpurely anatomical data and attacked itfrom the embryological side. Packard(’7), followed by Graber (’79), foundfour cephalic somites: antennal, man-dibular, first and second maxillary.Viallanes (’87) however, wrote themost important contribution upon thesubject after studying the developmentof the nervous system in insects anddecapod crustacea, and summarized hisresults as follows.

" La tSte de 1’ Insecte est forme parsix zoonites, trois sont prbuccaux ettrois post-buccaux. Le premier zooniteporte les yeux composs et les ocelles.Le deuxiime les antennes. Le trois-igme, qui est d6pourvu d’appendices,porte le labre, pi6ce qui, pas plus chezles Insectes que chez les crustacs, ne

peut 8tre consid6r6e comme le r6sultatde la soudure de deux appendices. Lequatl’ibme zoonite porte les mandibules,le cinquime les mg.choires, le sixiimela lgvre infrieure." These conclusionshave been confirmed by Wheeler (’93),Heymons (’95, ’97) and others.Rudimentary intercalary, or preman-

dibular, appendages have been found

in Anurida (Wheeler ’93, Claypole’98) and Campodea (Uzel ’97), andthe last two authors have homologizedthem with the crustaceaa secondantennae. I may add that rudimentarychitinized intercalary appendages per-sist in adults of Tomocerus, Orchesellaand other Collembola.

Six cephalic somites are the mostthat have been admitted upon embryo-logical grounds--but I am convincedthat six are not adequate. To provethis statement, I must give a prelimi-nary summary of some recent studiesupon the anatomy and development ofapterygote mouth-parts.The hypopharynx in Collembola and

Thysanura consists of three parts: a

median ventral lingua and two dorso-lateral su2berlinguae hitherto termed

" paraglossae," but quite distinct fromthe labial structures with the samename. In the embryo of Anuridatnaritima, the superlinguae originate as

a pair of simple papillae between themandibles and first maxillae and slightlynearer the median plane. The super-lingual anlagen are ectodermal evagi-nations containing intrusive mesodermand are histologically undistinguishablefrom the anlagen of the remainingappendages. The lingua appears as a

subsequent and quite independentmedian evagination of the first maxil-

lary segment and becomes supportedby a pair of lateral chitinous stalkswhich originate in superficial groovesof the germ band.Soon after involution has occurred,

just seven pairs of cephalic ganglia are

August 899. .PS 393

seen and--important facts- the thirdpair belongs to the intercalary segmentand the fifth to the superlingual somite.The lingua has no ganglia. Later, thefirst three pairs unite to form the supra-and the remaining four, the suboeso-phageal ganglion.More conclusive proof that the inter-

calary and superlingual appendagesrepresent primitive segments, of whichthere are seven, could hardly beexpected.

In Campodea (Uzel ’98) and Ephe-mera (Heymons ’96) the hypopharynxoriginates as three independent anlagenand several authors have held it to

represent a somite upon anatomicalgrounds. The hypopharynx of highlyspecialized insects, however, I find tobe homologous with simply the linguaof Collembola and Thysnura, althoughthe superlinguae are represented in themore generalized Pterygota but haveusually been overlooked or disregarded.Among Apterygota the lingua and

superlinguae do not unite, althoughtheir three cavities become basally con-fluent with the general body cavity.In Orthoptera and Ephemeridae, how-ever, the superlinguae are firmly unitedwith the lingua. Although often con-

spicuous in the latter group (Vayssi6re’Sz), the superlinguae are less so inOrthoptera but I have found them asdistinct lobes in all families of theorder. The chitinous lingual stalks,important in Collembola and Cam-podea, become reduced and function-less in Machilis and Lepisma but occuras rudiments even in Orthoptera,

including Hemimerus (Hansen ’94).Miall and Denny (’86) have figuredthem for Periplaneta and I have foundthem clearly in Melanoplus femoratus.There are striking and detailed agree-

ments between the anterior somites ofinsects and decapod crustacea. Vial-lanes (’87) and Hansen (’93) haveemphasized the fact fi’om their respec-tive standpoints of embryology andcomparative anatomy. My own results,confirming and supplementing theirviews, may partially be expressed intabular form. Between such divergentgroups, of course, homologies indicatenothing nore than a parallelism indevelopment.

EQUIVALENT PAIRED ORGANS.

SomiXe ITre aoda Cruslac

Compound eyes Compound eyesAntennae AntennulesIntercalary appendages Antennae

4 Mandible MandiblesSuperlinguae First MaxillaeFirst Maxillae Second MaxillaeLabium First Maxillipede

WORKS CITED.

Claypole, A. M. ’98. The Embryologyand Oggenesis of Anurida maritima (Gudr.).Jour. morph., vol. I4.

Hansen, H. J. ’93. Zur Morphologie derGliedmassen und Mundtheile bei Crustaceenund Insecten. Zool. anz. jhg. x6.Hansen, H. J. ’94. On the Structure and

Habits of Hemimerus talpoides Walk. En-tom. tidsk, arg. 5.Heymons, R. ’95. Die Segmentirung des

Insectenk6rpers. Abh. preuss, akad. wiss.Berlin.Heymons, R. ’96. Grundztige der Ent-

wickelung und des Kirperbaues yon Odona-ten und Ephemeriden. Abh. preuss, akad-wiss. Berlin.

394 t:’S YCI.E. [August x899.

Heymons, R. ’97. Entwicklungsgeschicht-liche Untersuchungen an Lepisma sacchar-ina L. Zeits. wiss. zool. bd. 6..Huxley, T. H. ’77. A Manual of the

Anatomy of Invertebrated Animal.Kolbe, H. J. ’89-’93. Einfiihrung in die

Kenntnis der Insekten.Miall, L. C. and Denny, A. ’86. The

Structure and Life-history of the Cockroach.Packard, A. S. ’71. Embryological Studies

on Diplax, Perithemis, and the ThysanurousGenus Isotoma. Mem. Peab. acad. sc. no. 2.

Packard, A. S. ’98. A Text-book of Ento-mology.Sharp, D. ’95. Insecta. Camb. nat. hist.

Uzel, H. ’97. Vorliufige Mittheilung tiberdie Entwicklung der Thysanuren. Zool. anz.bd. 2o.

Uzel, H ’98. Studien tiber die Entwicklungder apterygoten Insecten. Berlin.Vayssire, A. ’82. Recherches sur l’or-

ganization des larves des ]phdm(!rines. Ann.sc. nat. zool. sdr. 6, t. 13.

Viallanes, A. ’87. tudes histologiqueset organologiques sur les centres nerveux etles organes des sens des animaux articuls,Ann. sc. nat. zool. sdr. 7, t. 4.Wheeler, W. M. ’93. A contribution to

Insect Embryology. Jour. morph, vol. 8.

DESCRIPTIONS OF THREE NEW SPECIES OF ALEURODIDAEFROM BRAZIL.

BY ADOLPH HEMPEL S. PAULO BRAZIL.

Aleurodes korrldus n. sp.- Pupa-case.-Length, mm. elliptical in outline, flat;light yellow in color. The dorsal surface is

covered with white secretion, arranged in

a median longitudinal row, and a submar-

ginal row on each side. Around the marginthere is also a very short fringe of whitewax, These details are however obscured

by a mass of long yellowish, hair-like secre-

tion, that envelopes each individual. De-nuded of wax, the margin is found to be

doubly crenulated, with the posterior end of

the body rounded and the anterior end

forming an obtuse angle. The dorsum is

slightly wrinkled, and has a short median

longitudinal ridge, extending from the ante-

rior end to nearly the middle of the body.Vasiform orifice subelliptical, broader

than long. Operculum hemispherical,nearly fitting the orifice, the free end

notched. A long seta is situated on each

side of the orifice; two on the caudal end

of the body; and two on the ventral surface

of the body just cephalad of the middle.

No traces of antennae or legs were found.

Adult .--1.o8 mm. long, yellow, eyesblack; wings transparent, yellowish, coveredwith a white powder. Antennae of sevenjoints. Joints 3-7 fine, cylindrical, slender;joint 2 large, club-shaped. Legs long andslender, nearly reaching to the apex of theclosed wings.Hab.--On the underside of leaves of

guava, Psidium sp., from S. Paulo, Brazil.

Accompanied by a species of dnt (Cremas-togaster).Aleurodesfunijbennis n. sp.--Puba-case.--

Elliptical, convex, black, 1.8 ram. long.There is a prominent median longitudinal,dorsal ridge, and about six transverse fur-rows. The lateral margin is thick with a

conspicuous groove on the dorsal surfaceand a short fringe of white wax on the ven-

tral surface. Near the posterior end, aroundthe vasiform orifice, there is a large hemi-

spherical area, nearly transparent, but dustedwith white secretion. The lateral margin is

slightly notched in places, but not crenu-

lated. Vasiform orifice hemisphericaloperculum small, rectangular, fitting the

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