SMITHSONIAN MISCELLANEOUS VOL

alarge,slitlikeopening (a) between^theventral,orouter,ramiof the secondvalvulae (rivlo), which leads into a small cavity into which the oviductappears to open, but the internal

anatomy

couldnot be satisfactorily studied in the dried specimens on which this descrip- tionisbased.

As

willbe

shown

latera similar but

much

largerpouch inMagicicadaisthegenitalchamber,receiving theopeningsboth of the

OvipositorofAmblydisca gigas (Cicadellidae).

A,genitalsegmentsandovipositor.

B, seventh segment removed, showing first valvifer in pleural position on side ofeighth segment,andexposingrudimentaryeighthsternum.

C, baseof rightfirstvalvula,mesalview,showingconnectionofinnerramus (rivli) with ninth tergum.

.D, rightsecondvalvifer andbasal partsofsecond andthirdvalvulae,mesal view,showingarticulation (/>) ofsecondvalviferwith ninth tergum,andtergal muscles _(6,7) of valvifer.

median

oviduct and the spermatheca (fig. 32,

GC).

In Magicicada, however,thereis a second, posterioropening

from

thegenitalcham- ber between the bases of the second valvulae.

A

posterior opening could not be found in Amblydisca, and it has not been observed in any homopteron except

two

species of cicadas.

The

structure in Amblydisca,therefore, so far ascan be judged

from

dried specimens, is the

same

as that described for

Homoptera

generally by other writers. (See Holmgren, 1899; Myers, 1928;

Weber,

1930.)

NO. 8 INSECT

ABDOMEN

SNODGRASS 09

The

exposed part of the ninthabdominal segment of Amblydisca

(fig. 28A,

IXT),

as in

Homoptera

generally, consists of the large tergum.

The

ventral part of the segmentis

membranous

anddeeply concave,forminga cavityin whichare lodgedtheproximal parts of the third valvulae and the shaft of the ovipositor.

The

ovipositor consists of

two

pairs of broad, thin valvulae, the first

and

the second (fig. 29 A, ^iVl, 2VI), mostly concealed be- tweenthe widethird valvulae ₍jF/).

The

planes of the valvulae are vertical.

The

first valvulaelie closeagainst the outer surfaces of the

IXT

Fig.29.

—

^{Muscles of}the ovipositorof Amblydisca gigas.

A,right half ofovipositorandninth segment, mesal view.

B, rightfirstvalviferandfirstvalvula,mesal view.

secondpair,

and

thetwo oneachsideare firmly butmovablyattached by the usual interlocking grooves and ridges.

The

second, or inner, valvulae are conspicuously serrate along their dorsal margins (A, 2VI) ;at theirbases they are unitedwith eachotherbya

membranous

fold,but formost of their lengththey are free, though closely ap- pressed.

Each

first valvula has

two

^{proximal rami (figs.} 28^C, 29 B), a ventral outer

ramus

{rwlo) attachedto the anterior angle of thefirstvalvifer (iVlf),anda dorsal inner

ramus

^(rivli) which expands in a small triangular plate (in) attached to the lower an- terior angle of the ninth tergum (fig. 28C, n,

IXT). The

second

90 SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 89 valvula has asingle basal

ramus

(fig. 28 D, ^r2vl), whichis attached to the anterior end of the secondvalvifer {sVlf), and lies against the concave margin of the inner

ramus

of the first valvifer (fig.

29 A).

The

^first valvifer (fig. 28B, iVlf) is a triangular plate attached posteriorly by

membrane

to the anterior marginof the paratergite {pt) of the eighth segment, and ankylosed with the lower anterior part of the ninth

tergum (IXT).

In the normal positionit is con- cealed by invagination within the seventh segment (A).

The

inter- segmental

membrane

between the seventh and eighth segments (B,

Mb),

^therefore, extends forward

from

the lower end of the eighth tergum along the dorsal margin of the valvifer to the rudimentary eighthsternum (VlllSfn) beneaththe anteriorendsof thevalvifers.

To

the anteriorendofeachfirstvalviferisflexiblyattached the outer

ramus

of thefirstvalvula ^(figs. 28B, C, 29 A,B, rivlo) ;the inner

ramus

of this valvula (figs. 28C, 29B, rivli), as already noted, is firmlyattachedbya smallplate

(m)

to the loweranteriorangle (n) of the ninth tergum,

mesad

of the first valvula.

A

muscle arising ontheeighthtergum (fig. 28B,j) ^isinsertedonthe dorsal margin of the first valvifer (fig. 29B, j).

The

^{first valvifers} are not freely movable because of their posterior ankyloses with the ninth tergum, but they are flexible, and the contraction of their muscles evidently

must

elevate their anterior ends and produce a depression of the distal part of the ovipositor.

A

pair of short thick muscles attached laterallyon the valvifers and internallyonthe mesalplates of the inner rami of the first valvulae, are probably antagonistic tothe dorsalmuscles of thevalvifers.

The

secondvalvifer(fig. 28 D, 2Vlf) isa strong, elongatesclerite havingthe

ramus

of thesecondvalvula{2VI) attachedtoitsanterior end, and the base of the third valvula (3VI)

movably

articulated to its posterior end. In the normal position the second valvifer is

mostly concealed, in a lateral view (A), by the first valvifer.

The

second valvifer is movably articulated at a point

somewhat

beyond the middle of its dorsal margin to a condyle (D, _p) on the lower end ofa strong anterior ridge (r) of the inner surface of the ninth tergum (C,

IXT). Two

large antagonistic muscles arising on the ninth tergum ^(figs. 28 D, 29 A, 6, 7) are inserted onthe opposite ends of the second valvifer {bVIj). These muscles evidently rock the valvifer

up

and

down

onthe fulcrumof the ninth tergum,and thusimpart astrongback-and-forth

movement

to thesecondvalvula attachedby its

narrow

basal

ramus

(fig. 28 D, r2vl) tothe anterior endof thevalvifer.

The

secondvalvulaeslidefreelyontheirtracklike

NO. 8 INSECT

ABDOMEN

SNODGRASS 9^

connections with the first valvulae, but since the second valvulae are unitedat theirbaseswitheachother, the

two

innerblades of the ovipositor, which are serrated on their dorsal margins (fig. 29 A, 2VI), must

work

inunison betweentheouter^firstvalvulae.

The

first valvulae^also

may

have

some

independent

movement

producedbythe muscles of the first valvifers, but the writer has not observed the cicadellidovipositor in actionon a living specimen.

An

interesting account of the structure of the valvulae in the cicadellid ovipositor, and their relations to one another is given by Balduf _(1933).

The

anterior valvulae, however, are referredto the

"seventh sternite", and the second or inner pair to the ^"eighth sternite." Thiserrorprobablyarises

from

overlooking the true first

segmentof the abdomen, which is partially united with the second, though in no insect are the valvulae connected with the sternal plates of their segments.

MAGICICADA SEPTENDECIM (lINNAEUS)

The

well-developed ovipositor of the Cicadidae furnishesan easily studied example of the structure of the ovipositor typical of the Hemiptera.

The

17-year cicadahere described,however,hasa curious and unusual developmentof the genital chamber, which is provided with asecondaryposteriorpassagegivingexit totheeggsdirectly into the channel of the ovipositor.

Generalstructure of theabdomen.

—

There has been so

much

mis- information given outon the subject of the

abdomen

of the cicada thatitwillbe permissibletodevote alittle

more

attentiontothe general abdominalstructureof thisinsectthan

would

be necessaryotherwise inconnection with a study of the ovipositor.

The

general

form

of thefemale

abdomen

inMagicicadaseptendeciut

is

shown

at

A

of figure 30.

At

its base the

abdomen

is broadly but movably joined to the thorax, but the connecting parts are mostly concealedbyoverlapping parts of the metathorax.

When

^thethorax andthe

abdomen

are

somewhat

pulled apart, as

shown

at

B

of the

same

figure,itisseen that thereliesintheinfolded

membrane

between the metatergum (Ts)

and

the first abdominaltergum (IT) a well- developed though

narrow

postnotalplateof the metathorax

(PN3),

whichbears the large thirdphragma,andis fused ventrallywiththe metapleural epimera

(Epm^)

inthe usual manner.

On

each side of the

dorsum

the postnotumretainsa flexible scleroticconnection (a) with thefirstabdominal tergum.

The

latter (IT) isanarrow,trans- verse plate united with the second tergum {I

IT)

; its lateral part

92

presentsanenlarged oval area (b), which corresponds withthe area of thesound-producing cymbalof the male.

The

sternal platesof thefirst and second abdominal segmentsare highly modified,andthey are separatedbyadeepinflectionthatforms a large ventral cavity at the base of the abdomen. This cavity is

ordinarilyclosed to a

narrow

slit between the sternal plates, and is

IT IIT

Fig.30.

—

AbdomenofMagicicadascptcndccim (Cicadidae).

A,entireabdomen andbaseofthoraxofadult female.

B,details of connection betweenthorax and abdomen, lateral view.

C, ventralplates ofmetathoraxand^firstandsecondabdominalsegments.

D, baseofabdomenofmaturenymph.

E, tenthandeleventhsegmentsof adult.

a, hinge between postnotum of metathorax and first abdominal tergum; bj lateral areaof first abdominal tergum on which cymbalof maleis developed;

c,lateralarmoffirstabdominalsternumwithexpanded end (d) onwhichtergo- sternalmuscleisattached;e,posteriormedianplateoffirststernum;/,anterior median plate of second sternum; g, lateral arm of second sternum forming marginalrimoftympanum {Tin).

butlittleevidentina casualexaminationof a dried specimen. In the malecicada the cavityis

much

largerthaninthe feinaleandcontains the so-called "resonance" membranes, or " mirrors", which are

now

regardedas

tympana

for the reception of soundvibrations, since

ithasbeen

shown

by Vogel (1923) that chordotonal organs, situated inthelower endsofthesecond abdominal tergum,areconnected with their lateral extremities.

The

^{tympanal cavity can} be opened and

NO. 8 INSECT

ABDOMEN

SNODGRASS 93 closed by

movements

of levation anddepression of the

abdomen

on the lateralhinges (fig. 30B, a) betweenthe postnotum andthe first

abdominal tergum, the

movements

beingproduced bythe dorsaland ventralmuscles of thefirstabdominalsegment.

The

structure of the firstand second abdominalsternaand of thetympanalcavitybetween

them

isessentiallythe

same

inbothsexes,butitis

more

simpleinthe female.

The

firstabdominal sternum ^{of the} femalecicada liesimmediately behind the

narrow

postcoxal

arms

of the metathoracicepimera (fig.

30C,Pc.v). Itconsistsof

two

parts.

The

first isananterior,median, triangular plate (IS) having its lateral angles prolonged as a pair of

arms

(c) fusedwiththe postcoxal bridges (Pcx),buteach termi- nating in a lateral expansion (d), on which are attached the tergo- sternal muscles of the first abdominal segment.

The

secondplate is a median, quadrate sclerite (e) flexibly hingedto the anteriorplate (IS), and extending

upward from

the latter in the anterior wall of thetympanalcavity(B,^).

The

^spiracles of the firstabdominal segment (fig. 30^{B, C,} ISp) are containedinperitremalscleritesfusedwiththe lower,endsofthe metathoracicpostnotum

(PN3). They

open directly intothegreatair

chamber

oftheabdomen.

The

sternumof thesecondabdominal segmentconsists,asdoes that of the first segment, of

two

parts, onepart exposed, the other con- cealedinthetympanalcavity.

The

exposedpart ofthesternumisin thiscasethe posteriorpart,which forms anarrow,transversebridge betweenthelower ends of the secondabdominal tergum (fig. 30 A, B, C, IIS), with which it is solidly continuous.

The

anterior part of the secondsternumisaweakermediansclerite (C, f) turned up-

ward

on the anteriormarginof the posteriorsclerite inthe posterior wall of the tympanal cavity (B, /)^{; its} dorsal margin meets the posteriorplateof the firststernum (e) inthetransverse fold of the roof of thecavity.

The

lateralangles of the anterior scleriteof the second sternum (C, /) areproducedintoslender bars (g) ^thatextend outwardtomeetthelateralextremities of the posteriorsclerite,

where

eachendsina smallexpansioncontainingoneof thesecondabdominal spiracles (IISp).

Between

the

arms

_{(g) of the}firstsclerite andthe lateral parts of the second sclerite are the oval glistening

tympana

{Tin), or so-called "mirrors".

The

chordotonal sense organs con- nected with the

tympana

(inthemale) are saidtobe containedinthe tubercles {h) locatedatthe ventral lateralangles of the secondseg-

ment

wherethetergum

and

thesternumare confiuent.

The

thick cor- rugated

membranes {Mb)

inthe anterior wall of thetympanalcavity are intersegmental

membranes

between the first and second sterna.

94 COLLECTIONS VOL. 89

The

description of the basal parts of the

abdomen

of the cicada givenby Vogel (1923) inconnectionwithhisaccount of the chordo- tonalorgans,though minutein detail,isnot morphologicallysoundin everyrespect.

The

anteriorplateof thesecond sternum (fig.30C, /) Vogel regards as the first abdominal sternum, and he consequently refersthe

tympana

andthesecondspiracles tothefirstabdominalseg- ment.

The

posterior sclerite of the second sternum (IIS), bearing the ^"auditory capsules " (h),he callsthesecondsternum.

Much

of thisinterpretationisclearly in error sinceitdisregards the truefirst

sternumandthefirstabdominal spiracles,whichlatterVogelassigns to the thorax.

The

difficulty of properly disposing of the first ab- dominalspiracles inthecicadaarises

from

thefactthatthe spiracular peritremes in the adult insect are fused with the lower posterior marginsof themetathoracicpostnotum (fig.30B, C,

FN3),

thelower endsof which areunited withtheepimera;but the observation that thespiracles in questionlie behind theinternal intersegmental ridge bearing the lobes of the third

phragma

shows conclusively that thesespiraclesbelongto thefirstsegmentof the abdomen.

The

true relationsofthe basal parts of thecicada's

abdomen

are unmistakable inthemature

nymph

ofMagicicada (D).

The

firstabdominalsternum

ishere a simple triangularplate (IS) lying immediately behindthe metathoracic subcoxae,

and

the first abdominal spiracles {ISp) lie in the

membranous

lateralparts of the

dorsum

of the firstsegment.

The

tergum and sternum of the second segment (IIT, IIS)

show

no particular modifications, and the ventral tympanal cavity is not developedin the

nymph.

One

of the mostcurious aberrations in entomological morphology

isthetendencytoregardthegreatair

chamber

of thecicada's

abdomen

as a part of the digestive system.

The chamber

is a thin-walled sac always filledwith gas,but never containingliquid. Yet, thecicada's stomach

may

be distended with liquid food.

The

idea that the air sacisa diverticulum of thestomach

was

firstproposed

by

Hickernell (1920) on the basis of histological sections, which seernedto

show

a connection between the

two

organs.

The

question

was

later dis- cussed in the affirmative by Hargitt (1923) and by

Myers

(1928).

Ifthe air sac lacks taenidia

and

evena chitinous lining these points do notprove thatitis not of tracheal origin, since tracheal sacs do not usually contain taenidia, and

some

investigators have failed to findchitin in their walls.

The

^abdominalairsacof thecicada,as

may

be

more

clearlyseeninothergenera than Magicicada, opens directly to the exteriorthroughthe ^firstabdominal spiracles;and invarious places large, open tracheal tubes are given off

from

its walls. In

NO. O INSECT

ABDOMEN

SNODGRASS 95 Magicicada there is a tubular extension

from

the sac that proceeds inthe direction of the stomach, but the writer behevesit goes into thefilter

chamber

andnot into the stomach lumen,thoughthe facts could not be

more

closely investigated forthe lackof freshmaterial.

However,

the anatomical incongruityofhaving a diverticulum of the stomach openingto theexterior througha pair ofspiracles suggests a

human

error ratherthan a lapse of nature.

Most

of the visceral organs of the cicada's abdomen, except the stomach,whichliesanteriorly, are

crowded

intothe rearpart of the

abdomen

bytheposteriorextension of theairchamber,which endsin the seventh segment.

The

turgid

form

of the middle part of the

abdomen

(fig. 30

A),

therefore, presents the shape of the air sac.

The

region between the second and the eighth segments contains a succession of regular tergaland sternal plates.

The

lateral edges of the terga are inflected to meet the sterna, which are pleurosternal plates, there being no interveningpleurites or otherlateral sclerites.

In the adult, the spiracles of these segments are containedin small peritremal sclerites united with the anterior lateral angles of the sterna;inthe

nymph

thespiracleshavethe

same

positionbut theylie in

membranous

areasbetweenthetergalandsternalplates (figs.11 A,

30D).

The

tergumof the seventhsegment doesnotdiffer

from

theterga preceding it.

The

seventh sternum (fig. 30 A, VIIS), however, is shortened, butitsdeeplyemarginateposterioredge underlapsthebase of the ovipositor (Ovp).

Above

the seventhsternumisa small ves- tibularcavity (fig.32 A,Vst),inthe anteriorwall ofwhichisa large genitalopening (a) abovea small fold (VlllStn), which isthe pos- terior lip of the otherwise invaginated eighth sternum.

The

genital aperture

may

be exposed by depressing the seventh sternum, orby pulling thelatterforward (fig.31A,a). Itleadsintoa largecopula- tory pouch

(GC),

which, as will be

shown

later, isthe true genital chamber.

The

eighth segment is exposed dorsally but itsventral parts are normallyconcealed within the seventh segment.

The tergum

is de- clivous behind the seventh tergum (fig. 30 A,

VIIIT)

; its lateral partsare

narrowed

andarewidelyseparated

from

the sternal region of its segment.

The

anterior end of the eighth sternum appears as a small foldbeneaththeopening of thegenital

chamber

(figs. 31A, 32 A, VlllStn), butmost ofthe sternal plateis reflected anteriorly

upon

the floorofthe

chamber

(fig. 32B, VlllStn) andistherefore concealed within thelatter.

The

exposed anterior (anatomically pos- terior) end of the eighthsternumisconnectedby

membranous

folds