Article beginning on page 391.
Psyche 8:391-393, 1897.

Full text (searchable PDF)
Durable link: http://psyche.entclub.org/8/8-391.html

The following unprocessed text is extracted from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

PSYCHE.
THE SEGMENTATION OF THE INSECT HEAD.
BY JUSTUS WATSON FOLSOM, CAMBRIDGE, MASS. The elucidation of the primitive
segments in arthropods is a most inter-
esting and difficult morphological
problem. The rule of Savigny -
emphasized by Huxley and others -
that arthropods are fundamentally con-
structed of successive rings, each of
which may bear but one pair of pri-
mary appendages, although now un-
doubted, has never been thoroughly
substantiated when applied to the
hexapod head. After years of argu-
ment, morphologists still disagree as to the number of somites composing the
highly differentiated heads of i'nsects. Compare the latest text-books in respect to the subject. Kolbe ('go) recognizes
five, as follows :
I.
Ursegment : Fuhler, Augen, Oberlippe.
2.
L‰ Oberkiefer oder Mandibeln.
3-
ct Unterkiefer oder Maxillen.
14- " Zunge oder Innenlippe.]
5-
C‰ Unterlippe.
Sharp ('95) says, " Morphologists
are not yet agreed as to their number,
some thinking this is three while others place it as high as seven : three or four being, perhaps, the figures at present
most in favour, though Viallanes, who
has recently discussed the subject, con- siders &, the number suggested by
Huxley, as the most probable.
Cho-
lodkovsky is of a similar opinion."
Packard ('98) gives six :
I. Ocellar (Protocerebral). Compoundandsimple eyes. a. Antenna1 (Deutocerebral). Antennae.
3. Premandibular, or inter- Premandibular append- calary (Tritocerebral). ages.
a. Mandibular. Mandibles.
5. first Maxillary. First Maxillae.
6. Second Maxillary. Second Maxillae, or Lab- ium. Post-gula, gula,
submentum, hypopha-
rynx, (lingua, ligula),
paraglossae, spinneret.
Upon anatomical grounds, different
observers have recognized from one to
seven head segments. As mentioned
by Packard ('98), Burmeister found
only two ; Cams and Audouin three ;
MacLeay and Newmari four; Straus-
Durckheim seven. Huxley ('77) said,
"It is hardly open to doubt that the
mandibles, the maxillae, and the labium, answer to the mandibles and the two
pairs
of maxillae of the crustacean
mouth. In this case, one pair of
antennary organs found in the latter is
wanting in insects, as in other air-
breathing arthropods, and the existence
of the corresponding somite cannot be
proved. But if it be supposed to be
present, though without any appendage,
and if the eyes be taken to represent




================================================================================

the appendages of another somite, the
insect-head will contain six somites."
Huxley's conclusions were the most
satisfactory that could be derived from
a study of the completed organs alone
and reduced the problem to these ques-
tions : Do the eyes represent a somite?
Is another antennal segment represented
in insects? Do the labrum and hypo-
pharynx represent distinct segments?
Authors began to realize the impossi-
bility of settling the problem upon
purely anatomical data and attacked it
from the embryological side. Packard
('71)~ followed by Graber ('79), found
four cephalic somites: antennal, man-
dibular, first and second maxillary,
Viallanes ('87), however, wrote the
most important contribution upon the
subject after studying the development
of the nervous system in insects and
decq-pod crustacea, and summarized his
results as follows.
' La tete de I' Insecte est formfie par
six zoonites, trois sont pr&uccaiix et
trois post-buccaux. Le premier zoonite
porte les yeux compos6s et les ocelles.
Le deuxifeme les antennes. Le trois-
&me, qui est dSpourvu d'appendices,
porte le labre, pifece qui, pas plus chez les Insectes que chez les crustac6s, ne
pent &re considirhe comme Ie resultat
de la sondure de deux appendices. Le
quatri&mc zoonite porte les mandibnles,
Ie cinquihe lcs mAchoires, Ie sixifime
la liivre infSrieure." These conclusions have 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), and
the last two authors have homologized
them with the crustacean second
antennae. I may add that rudimentary
chitinized intercalary appendages per-
sist in adults of Tocnocerus, Orchesella and other Collembola.
Six cephalic somites are the most
that have been admitted upon embryo-
logical grounds -but I am convinced
that six are not adequate. To prove
this statement, I must give a prelimi-
nary summary of some recent studies
upon the anatomy and development of
apterygote mouth-parts.
The hypopharynx in Collembola and
Thysanura consists of three parts: a
median ventral lingua and two dorso-
lateral su-perlinguae, hitherto termed
6' paraglossae," but quite distinct from the labial structures with the same
name. In the embryo of Anurida
tnaritima, the superlinguae originate as a pair of simple papillae between the
mandibles and first maxillae and slightly nearer the median plane. The super-
lingual anlagen are ectodermal evagi-
nations containing intrusive mesoderm
and are histologically undistinguishable from the anlagen of the remaining
appendages. The lingua appears as a
subsequent and quite independent
median evagination of the first maxil-
lary segment and becomes supported
by a pair of lateral chitinous stalks
which originate in superficial grooves
of the germ band.
Soon after involution has occurred,
just seven pairs of cephalic ganglia are 392 PSYCHE. [~ugust ~ 8 9 ~ .
. -
- -




================================================================================

August 1899.1 PSYCHE.
seen and- i~nportait facts -the third
pair belongs to the intercalary segment
and the fifth to the superiingual somite. The lingua has no ganglia. Later, the
first three pairs unite to form the supra- and the remaining four, the suboeso-
phagcal ganglion.
More conclusive proof that the inter-
calary and superlingual appendages
represent primitive segments, of which
there are seven, could hardly be
expected.
In Campodea (Uzel '98) and Ephe-
mera (Heymons '96) the hypopharynx
originates as three independent anlagen
and several authors have held it to
represent a somite upon anatomical
grounds. The hypopharynx of highly
specialized insects, however, I find to
be homologous with simply the Zingxa
of Collembola and T~~s.,IILI~-~, although the superlinguae arc represented in the
more generalized Pterygota but have
usually been overlooked or disregarded.
Among Apterygota the lingua and
superlinguae do not unite, although
their three cavities become basally con- fluent with the general body cavity.
In Orthoptera and Ephemeridae, how-
ever, the s~~perlinguae are firmly united with the lingua. Although often con-
spicuous in the latter group (Vayssifere 82), the superlinguae are less so in
Orthoptera but I have found them as
distinct lobes in all families of the
order. The chitinous lingual stalks,
important in Collembola and Cam-
podea, become reduced and fnnction-
less in Machiiis and Lepisma but occur
as rudiments even in Orthoptera,
including He~nimems (Hansen '94).
Miall ~ind Denuy ('86) have figured
them for Periplancta and I have fourid
them clearly in Melanoplus fernoratus.
There are striking and detailed agree-
ments between the anterior somites of
insects and decapod crustacea. Vial-
lanes ('87) and Hansen ('93) have
emphasized the fact from their respec-
tive standpoints of embryology and
comparative anatomy. My own results,
confirming and supplementing their
views, may partially be expressed in
tabular form. Between such divergent
groups, of course, liomologies indicate
rioLhing more than a parallelism in
development.
EQUIVALENT PAIRED ORGANS.
S4fe He.zafmlfi. Crxsfacm
I Compound eyes Compound eyes
2 A,,ten,,ae Anteiinutes
3 Intercalary appendages Antennae
4 Mandibles Alandiblcs
5 Superliugut~e Firs! Maxillae
6 Fhat Maxillae Second Maxillae
7 Labium First Maxillipedei
WORKS CITED.
Claypole, A. M. '98. The Embryology
and Oogenesis of Anurida maritima (Gudr.). Jour. inoi-ph., vol. 14.
Hansen, H. J. '93.
Zur Morphologie der
Gliedmassen und Mundtheile bei Crustaceen und Insecten. Zool. anz. jhg. 16.
Hansen, H. J. '94. On the Structure and
Habits of Hemimerus talpoides Walk.
En-
torn, tidsk. ax. 15,
Heymons, R. '95. Die Segmentirung des
InsectenkOrpers. Abh. preuss. alcad. wiss. Berlin.
Hey~nons, R. '96. GrundzUge der Ent-
wickelung und des KOrperbaues von Odona- ten und Ephemericlcn. Abh. preuss. dad-
wiss. Berlin.




================================================================================

[August iBqq.
Heymons, R. '97, Entwicklungsgeschicht-
liche Untersuchniigen an Lepisma sacchar- ina L. Zeits. wiss. zool. bd. 62.
Huxley, T. H. '77. A Manual of the
Anatomy of Invertebrated Animals.
Kolbe, H. J. '89-'93. Einftihrung 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 Thysanurous Genus Isotoma. Mem. Peab. acad. sc. no. 2. Packard, A. S. '98.
A Text-book of Ento-
mology.
Sharp, 1). '95. Insecta. Camb. nat. hist. Uzel, H. '97.
Vorliiufige Mittheilung tiber
die Entwicklungder Thysfinuren. Zool. anz. bd. 20.
Uzel, H '98. Studien tiber die Entwicklung der apterygoten Insccten. Berlin.
Vayssi&re, A. '82.
Ryherches sur 1'01-
ganization des larves des Ephh6rines. Ann. sc. nat. 2001. s&. 6, t. 13.
Viallanes, A. '87. etudes histologiques
et organologiqnes sur les centres nerveux et les organes des sens des animaux articulfes, Ann. sc. nat. zool. sir. 7, t. 4.
Wheeler, W. M. '93.
A contribution to
Insect Embryology.
Jour. morph. vol. 8.
DESCRIPTIONS OF THREE NEW SPECIES OF ALEURODIDAE FROM BRAZIL.
BY ADOLPH HEMPEL, S. PAULO, BRAZIL.
Aleurodes horridus n. sp. - Pupa-case.-
Length, I 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 margin there is also a very short fringe of white wax. 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 erenulated, with the posterior end of the hody 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. Variforin orifice subelliptical, broader than long. Operculinn 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 hody; and two on the ventral surface of the body just cephalad of the middle. No traces of antennae or legs were found. Adult $' .- 1.08 mm. long, yellow, eyes
black; wings transparent, yellowish, covered with a white powder. Antennae of seven
joints. Joints 3-7 fine, cylindrical, slender; joint 2 large, club-shaped. Legs long and slender, nearly reaching to the apex of the closed wings.
Hd.-On the underside of leaves of
gnava, Psidium sp., from S. Paulo, Brazil. Accompanied by a species of ant (Cremas- togaster).
Alezwodes fumfpennis n. sp.-Pupa-case,-
Elliptical, convex, black, 1.8 mm. 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 surface, and a short fringe of white wax on the ven- tral surface. Near the posterior end, around the vasiform orifice, there is a large liemi- spherical area, nearly transparent, but dusted with white secretion. The lateral margin is slightly notched in places, but not crenu- lated. Vasiform orifice hemispherical;
operculum small, rectangular, fitting the



================================================================================