Article beginning on page 409.
Psyche 5:409-413, 1888.

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PSYCHE.
NOTES ON SOME AYHID STRUCTURES.
BY JOHN B. SMITH, NEW BRUNSWICK, N. J.
DURING the season of 1890, the most
notable feature in New Jersey was the
enormous increase in the numbers of
the a$hididae. Naturdly, as complaints
of injuries were ~eceived, I was com-
pelled to pay some attention to these
insects, and a Bulletin of the Station has been prepared treating of some of the
more injurious forms. It is pirt of my
creed, whenever I look at an insect,
whatever its order, to see all I can, and so far as the characters are interesting, and bear at all on the philosophy of
economic entomology (for I believe
thi~t economic entomology is simply the
philosophic application of the facts as- certained by a technical study to the
practical needs of Agriculture), I do
not hesitate in presenting them in a
popular way in the Bulletins of the
Station, Sometimes the facts observed
have, or may have a technical bearing,
and as the Station Bulletins under pres- ent circumstances are hardly ranked as
technical publications I prefer to present them in another form in the technical
journals also.
The principal points studied were
and much more use than has been made,
in systematic entomology.
Perhaps, after the examination of
the heads of lepidoptera and diptera,
the most prominent feature that chal-
lenges obwrvation is in the eyes. These
do not have hexagonal facets as usually
described for insects, but there i? a
simple aggregation of quite strongly
convex circ~tlar lenses, each quite dis- tinct fi-om all the others, externally,
and each undoubtedly capable of receiv-
ing a wmplete image in itself. The very
strong convexity of the lens makes it
very probable that the insects :\re ex-
cessively short sighted. When the
head has been maceiated in potash, the
framework of the eye appears as though
the setting for the lenses had been
punched out with a round punch. I
take this to be a much nlore simple eye
formation than that of the faba8idae
for instance.
The antenna1 structure derives its
interest from the imbricated or scale
like markings of the surface, some-
times confined to the terminal joints
only, sometimes present on all, and
the beak and antennae. So far as the ' from the system of sensory pits or pores. latter organs are concerned there is room In reference to this last 1 have found
tor a great deal of histological work,
it invariable on all the specimens of the



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410 J's iJTH... [November-December I*
same species, and this o~~ght to f~wnish a most important character in the separ- ation of species. The systen~ is alike
in no two species hitherto examined by
me, tho~lgh this may not hold good
throughout the family.
Another very important point sfruck
me. In none of the wingless forms
does the poriferous system attain the
complexity found in the winged forms.
From the young louse just born, to the
pupa, the poriferous system remains
the same, and is very similar in all the species ; but when the winged form is
assumed, the specific poriferous system
makes its appearance. It is well to say
here, that I have not examined the true
sexes and can say nothing of any spe-
cies in the sexually perfect condition.
In all the wingless viviparous fernales
examined, the larval poriferous sjstem
was retained, and 1 cozclude therefore
tAai we have to do, ~eal@, with a true
~e$roductiorz anzozg lwval forms,
azd that wingless vizji$arous females
amo&g ajhididae are zot wzadure in-
sects ie a~zy serzse of the term; 6zd
that they rejresezt sim@y az arrested
7arvaZ stage, which uzdw 0th.~~ COB-
ditiom would develoj izto a wizged
form. The winged viviparous females
are ultimate or mature forms in which
both sexual elements are represented in
the form of the original germ cell,
wl~icl~ by budding, develops the embryo
brought forth. It seems rather elemen-
tary, bt~t equally necessary to explain, that the tenn '*b~idding" as used in
reference to this method of reproduc-
tion, is a budding of the germ cell, and not a budding from the body of the in-
sect; but in this latter sense 1 find that the term is quite generally understood.
With these, preliminary, observations
and conclusions, 1 will proceed to
details.
In all the aphides examined the first or basal joint is subglobose, stout and short ; the second is also short, but scarcely glo- bose ; the third is the first of the long joints and it is longer than either the 4th or sth, which are subequal in length,
and sometimes is as long as both to-
gether. The sixth, or terminal, is what
I have termed the whip joint, It en-,
larges gradually from the base for a
short distance and is then rather
abruptly narrowed fi-om one side, giv-
ing a false appearance of, segmentation. From thiiPoint it continues to the tip,
gradually tapering to a point. It is
flexible, and the resemblance to a whip
is not fanciful.




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November-December I+.] F's ZT&?B.
411
In the Wheat lause, Sz''ho~o$Ao~a
aveaae Fabr., the third joint is visibly imbricated only beyond the middle
while a11 the following joints are ob-
viously imbricated. The sensory pits
are confined to a single row of eleven,
extending from the base to beyond the
middle of the joint. The 4th joint has
no sensory pits and the 5th has a small
group near its tip, only. Thee6th joint
has at the point of greatest dilation, and just before the sudden narrowing, a
very distinct group of pits, and these
are permanent in all stages, and very
similar in all species- The absence of
these would be a matter of very high
systematic value.
Jn the Cabbage louse, Ajhis 6~assi-
cue Linn., the poriferous system is
entirely different. The 3rd joint is not, or b ~ ~ t faintly imbricated, ~ h i k the small, sensory pits are scattered all over the surface in no regular series and too \
numerous to coiint. In a case like
this I should expect a considerable
range of variation in the n~mber of
pits. The 4th joint is imbricated, as
are all the following, but 1x1s no sensory pits. The 5th joint is very like that of S. aveflae, as is also the 6th. In the
immature forms the 5th joint is furnished with a single large pit at tip, and the
mual small aggregation on joint 6,
A$his cucume~is Forbes, the Melon
louse shows a somewhat different type




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ot structure. All except the basal
In the Cherry aphis, AQzus cerasi
small joints are distinctly imbricated,
Fabr., the pores or pits are still larger, and the sensory pits are very much
and the structure of the pits is still better larger than in either of the preceding
brought out.
On the 3rd joint, which
species.
In this species the structure
with all subsequent ones is imbricated,
of the pits becomes more evident, but there is a series of eleven very large will not be further referred to here, as pits in a single line : the fourth joint is the Peach aphis affords a more satisfac- free of such pits : the 5th joint has a tory subject.
The 3rd joint in this single large pit near the tip, and the species has seven or eight sather irreg- sixth joint as usual has a small gro~~p, ularly placed pits, extending the full consisting here of a very large oval pit length of the joint. Joint 4 is free with four smaller ones grouped at one while 5 has a single large pit near the
side.
tip.
Joint 6 has the usual little aggre-
gation, one large pit, margined by sev-
era1 small ones.
Most interesting of all, is the Peach
aphid, A9h.i~ pe~sicae-gige~ E, F.
Smith. In this species the poriforous




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November-December 18go.J ~~~~~~. 413
or sensory system attains its most conl- plete development, so far as my obser-
vations extend. Every joint, except
the small basal laobs, is imbricated,
and each is furnished with sensory pits
or pores. The third joint is irregular
and knobby from the projecting margins
of the pits, which are numerous and
very large. The figure shows the ap-
pearance wd1, but it must be said that
the enlargement of 6, is only 8 that of
a, c, d, and e, so that it is really equal to the two follo~~ing joints in lex>gth. Joint four has also a large number of
pits, irregularly scattered on all sides, and this is the more remarkable since
in none of the other species is it pitted at all. Joint five has four lasge and
two sn~all pits on one side-other not
examined-? inoi-e also than in the
other species. On joint six, on the
contrary, the aggregation of pits is smal- ler than in the Cherry aphid, though
the number of small pits is greater.
' C~~riously enough, nothing in the larviil antennae indicates this extreme develop- ment in the mature form. All of the
wingless forins have this simple, single pit neai the tip of 5, and the usual
small group on 6. It has been already
indicated that in this species the struc- ture is best made out. This is due to
the fact that every part is more thorough- ly chitinized than in any other species
save JF. ce~*asz', and the action of
potash and carbolic acid is not so de-
structive, while the parts are sufficiently cleared for study. We see here that
we do not have simple pits to deal
with ; but rather special sense organs,
apparently not directly communicating
with the outer air, for on careful exam- ination a fine, tense membrane is seen
to close the opening, not from edge to
edge, but as if drawn over a projecting
.rim. It is on a side view that we best
get an idea of the structure which is
fairly well shown at f and g-. What
are the functions of these pits? Not
tactile, surely ! Olfactory ? Why should that require any tense membrane? Au-
ditory ? Here the membrane might
serve as a drum to catch the vibrations ; but why should there be such a differ-
erence in number? Why also do the
darker, more chitinized forms have .
these pits selatively so much larger?
These questions are easily asked ; but
I shall not try to answer them.
Besides the antennae 1 also studied
the n~outh parts of these insects and
find that there is some small difference in the structui-e here, shown in the fig- ures gil-en ; but scarcely worthy of
note, except in the case of the wheat
louse. In this species the beak is per-
haps shorter and bsoader than in the
others, while the ante-apical segment
1x1s on each side a peculiar flap, gouged from the body of the joint and covering
loosely the pit thus caused. This is
found in all stages of this species, and nothing like it has been found in any
other examined by me.
Within this beak are the four bristles,
two of them connate except at base,
which are supposed to represent the
maxillae and mandibles? the beak itself
being a modified labium. I wish to
decidedly state my disbelief in any such



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PSYCHE. [Xovember-December 1890.
homology. It is utterly unphilospho-
cal to accept without the clearest proof such a structural modification as this
change in position of the mandibles
would require, and the modification of
the ordinary labium into a beak of this* character is a process that ought to be
proven. It seems to be assumed that the
4'labium" of the hemiptera is the same
as the ''labium" of the diptera, e. g.
Cdex, and if this is so, I have a paper
now in press, in which I claim to prove
that this ''labium" in the diptera is
really only a modified galea, or a max-
illary structure. I hope to prove some
time in the future, when I can get the
necessary material, how this modifica-
tion of the hemipterous mouth came
about, and that the mandibles do not,
habitually, become internal mouth
structures so long as there are other
organs enough more naturally situated.
EXPLANATION TO BASE FIGURES.
Fig. x. Si$hon@Ao~a avenae. a, beak ;
b, bristles of mouth-"mandib1es" and "max- illae ;" c, antenna of winged viviparous female.
Fig. 2. A$his byassicae. al antenna of
wingless forms; 6, antenna of winged vivi- parous female ; c, beak of young lice ; d, beak of mature, winged form.
Fig. 3. A$his cacawze~is. Q, antenna of
winged viviparous female ; b, beak of wing- less forms.
Fig. 4. Myzus cerasi. al 3rd; 6. 5th;
c, 6th joint of antenna of winged viviparous female.
Fig. 5. A$Ah $ersicae-nige~. a, antenna
of immature forms, joints 5 and 6 ; 6, 3rd; c, 4th; d, 5th; e, 6th joint of antenna of winged viviparous female; fl sensory pit from front ; g, same from side.
NOTES ON TWO SPECIES OF DATANA WITH DESCRIPTIONS OF THEIR LARVAL STAGES.
Of all the closely related species of
this genus, the two which approach
.
each other the most nearly and are most
difficult to distinguish in the imago
state, are D. major and D. drexelii.
I have elsewhere called attention to the main feature by which they are to be
distinguished, which, after all, is only a matter of degree of coloration. The
species differ, or rather tend to differ, in other points beside the brightness of the costal shade, namely, in the more
entire outer margin of the primaries,
and the darker more eyen coloration of
the wings of D. major.
The size is the same in both species,
there are no markedly distinctive male
genital characters, and the lines and




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