THE OVIPOSITOR OF HEMIPTERA

VIIIT KT

VI. THE OVIPOSITOR OF HEMIPTERA

The

genital segments andtheovipositor of the

Hemiptera

present the followingcharacteristic features

:

1.

The

shaft of the ovipositor is

formed

of the first and second valvulae, thefirstbeingexternalandventral,thesecondinternal and dorsal.

The

second valvulae are generally united with each other.

eitherfora part or formostoftheir length.

2.

The

sternum of the seventh abdominal segment formsthe sub- genital plate of the female, and encloses a small vestibular chamber atthebase of theovipositor.

3.

The

eighthsegmentisexposeddorsally,butitslateralandventral partsare mostlyconcealed within the seventh segment.

4.

The

firstvalvifershavea pleural positionbelowthetergum on thesides of the eighthsegment, thoughtheirposterior angles

may

be flexiblyattachedto the ninthtergum.

The

^dorsalmusclesof thefirst valvifers arise on the eighthtergum.

5.

The

sternumof the eighthsegmentisrudimentary, being repre- sented generallybya

mere

foldof the integument below ^thebase of the ovipositor at the anterior end of the vestibulum.

The

genital

chamber

is correspondingly reduced in most cases to a small pocket beneaththegonopore;in

some

of the Cicadidae,however,thegenital

chamber

forms a large pouch into which open the median oviduct andthe spermatheca.

6.

The

^first valvulae have each

two

proximal rami.

The

outer

ramus

isflexiblyattachedtothe ventralangle of thefirstvalvif er;the inner

ramus

expandsina smallplate solidlyunited withthe anterior ventral angle of the ninthtergum.

A

muscle extends

from

the inner faceof thefirstvalvifertothe basalplateof theinnerramus.

8o

89

7.

The

ninth tergum is exposed, and usually large. Its anterior ventralangles areproducedforwardas extensionstowhichare united theinner ramiof thefirstvalvulae.

8.

The

secondvalvifershavea pleural position on thesidesofthe ninthsegment beneaththelateralmarginsof the ninthtergum.

Each

is movablyarticulatedwiththetergumata point near themiddleof itsdorsalmargin,andisprovided withantagonisticmuscles

from

the ninthterguminsertedbeforeand behindthe fulcrum.

9. Thereare generallynointervalvularscleritesinthe ninth venter, and tergosternalmusclesare absent intheninth segment.

10.

The

secondvalvulae are attached proximally, each bya single arcuate ramus, to the anterior end of the second valvifer, and the

ramus

slides on the concave margin of the inner

ramus

of the cor- respondingfirstvalvula.

11.

The

third valvulae are welldifferentiated

from

thesecondval- vifers; they

form

a pair of lobes ensheathing the distal end of the shaft of the ovipositor^;rarelythey are absent.

12.

The mechanism

ofthehemipterousovipositorisverysimple as

compared

with that of the gryllid ovipositor; its only muscles are those of the firstand secondvalvifers, andthe pair ofmuscles

from

the firstvalvifers tothe inner rami of the firstvalvulae.

13.

An

unusualconditionbringingaboutthedischarge of theeggs directlyintothe channel of the ovipositorexists in

some

of the Cicadi- dae, inwhichthegenital

chamber

formsa largepouch opening above the rudimentary eighth sternum,and has a secondposteriorexitbe- tweenthebases of thesecondvalvulae.

The

relationofthisstructure to the usual structure in other Hemiptera is notunderstood, andit

appearsthat themorphologyof the terminal parts of thefemalegenital ductsintheHemipteraisa subjectinneedof furtherinvestigation.

As

betweentheHeteroptera andthe

Homoptera

thereisnoessential differenceinthe structure of theovipositor. In each group, also,the ovipositor is well developed in

some

forms, and reduced or absent in others. According to the comparative studies of

Ekblom

(1926, 1930),anovipositorispresent

among

theHeteropterainthe families Saldidae, Nabidae,Lygaeidae, Veliidae, Gerridae, Mesoveliidae,Cor- izidae,

and

Corixidae,

and

is best developed in the Saldidae and Nabidae; but the organis well developed also in Notonectidae

and

Coreidae.

The

structure of thehemipterousovipositorwillbe

shown

in thispaperby examples taken

from

the Saldidae, Coreidae, Cicadel- lidae, andCicadidae. In connection with a study of the ovipositorit is important to understand the segmentation of the abdomen, since students of the Hemiptera are most frequently at fault concerning

INSECT

ABDOMEN

SNODGRASS 8i theidentityof the abdominal segments, on accountof the partial or complete suppression of the first segment. In order to understand themorphologyof the parts of the ovipositor described and figured by Ekblom, the following description of a saldid ^species, Pentacora ligata, isgivenasan introductoryexample.

PENTACORA

LIGATA SAY

The abdomen

ofPentacora (fig. 26

A)

isbroad and^{flattened, but} the genital region, including the seventh, eighth,andninth segments, formsa terminalenlargement supporting the ovipositor {Ovp).

The

VIRT IXT X

VIIIT IXT

Fig.26.

—

^Abdomen and ovipositor of Pentacora ligata (Saldidae).

A,entireabdomen.

B, genital and postgenital segments and ovipositor, showing rudimentary eighthsternumbeneath gonopore.

C, firstvalviferandfirstvalvula.

D,attachmentof innerramusoffirstvalvulatoninth tergum.

E, secondvalviferwith second andthirdvalvulae.

first tergum {IT) is well developed, its anterior margin forming a free fold overlapping the

narrow notum

and postnotum of the metathorax;but thesternumof thefirstsegment^iseithersuppressed or indistinguishably unitedwiththe second. Segments//to

VII

have largeparatergal plates

(^0

^{formingthe lateralmargins of thewide} pregenital region of the abdomen.

The

^{spiracles of these segments}

are situated ventrally in thelateral bordersof thesternal plates,but those of the eighthsegmentlieinthe paratergal lobes of the

dorsum

(B, pt)^.

The abdomen

ends withthe small tenth segment, or proctiger (X),

from

beneath whichproject thewidethirdvalvulae {3VI) with the shaft of the ovipositor

{Ovp)

between them.

The

seventh segment is funnel-shaped, expanded posteriorly. Its largesternum ^(fig. 26 A,

VIIS)

projects ventrally in a

median

lobe beneaththe base of theovipositor,anditsposteriormarginisinflected to

form

the ventral andlateral walls of a vestibulumconcealing the loweranterior parts of the eighth and ninth segments, andthe base of theovipositor.

The

eighth segment is mostly concealed within the seventh (fig.

26

A). When removed from

thelatter

(B)

it is seento consist of a completeannulus,thoughthe ventral partisreducedand

membranous.

Dorsally the segment presents a tergal plate

(VI

IIT), with small paratergal lobes (pt) containing the eighthspiracles;its lateralwalls are

formed

by large, triangular pleural plates, which are the first valvifers (iVlf); the

membranous

ventral part forms a small fold (VlllStn) atthebase of theovipositor,representing therudimentary eighth sternum.

The

genital opening appears to be situated above thesternalfoldbetweenthe bases of thefirstvalvulae,butitsexistence here could not be positively determined in the dried specimens examined.

Itis of particularinteresttonote thatthefirst valvifer (fig. 26B, iVlf) hasa true pleural positiononthesideofitssegment.

Crampton

(1929) mistakes the valvifer of the eighth segment in Hemiptera fora basivalvula, but the identity of the plate in questionis

shown

withoutdoubtbyits musculature, and by the factthat the first val- vula is directly connected with its ventral angle (C).

The

first valvula,however,hasaninner

ramus

(D,rivli)'whichcurves

upward from

its dorsal margin and is connected with a small plate

(m)

attached to an extension (n) of the lower anterior margin of the ninth tergum

(IXT).

This basal sclerite

(m)

of the inner

ramus

of thefirst valvulamight be regardedas a part of the valvula. inas-

much

as it is continuous ventrally with the latter by a fold of the connecting

membrane,

or it might be supposed to be a part of the ninth tergum^;butitis

more

probable thatitisa part of the

ramus

itself, since thereisinserted

upon

it ashort thickmuscle arisingon the inner face of the valvifer, which

would

appearto represent the basalmuscleof thegonapophysisin

Thysanura

(fig. 6F,gmcl). In anycase,the structure of the^firstvalvifer, andtheinnerconnection of the first valvula with the ninth tergum, as

shown

in Pentacora, are features characteristic of all the Hemiptera.

The movements

NO. 8 INSECT

ABDOMEN —

_{-SNODGRASS 83}

of thefirstvalviilaareproducedintheusual

manner

by musclesof the firstvalvifer arisingontheeighthtergum.

The

ninth segment has a large tergal plate (fig. 26,A,B,

IXT)

covering theback

and

sidesofthesegment;itsanteriorventral angles areextendedanteriorlywithin theseventhsegment,and, asjustnoted, they are here fused v^ith the basal plates of the inner rami of the first valvulae (D).

Below

each lateral margin of the ninth tergum

is an elongate lobe (B, 2Vlf),the outer wall of which isnot con- tinuously sclerotized, but presents a dorsal

and

a ventral plate (E, a, b).

The

lobe, however, is unquestionably the second valvifer (2Vlf), since it carries the second and the third valvulae (2VI, sVl).

The

second valvula is attached to the anterior end of the second valvifer by an arcuate basal

ramus

{rsvl), which slideson theconcavemarginof the inner

ramus

of thefirstvalvula.

The

large third valvula (3VI) arises

from

thedistalendofthesecond valvifer;the thirdvalvulae

form two

broadfree lobesembracingthe distalend of the shaft of the ovipositorbetweentheir concave mesal surfaces.

The

secondvalviferisarticulatedata pointnearthemiddle ofitsdorsalmarginto theloweredgeof theninthtergum,and

mus-

cles arising on the ^latter, inserted anteriorly and posteriorlyon the valvifer, rock the latter

up and down

and impart a back-and-forth

movement

to the second valvula attached to its anterior end.

The two

second valvulae probably

work

in unison because of their con- nection with each other.

The

true sternal region, or venter, of the ninthsegmentisthe

narrow membranous

wallbetweenthe

two

second valvifers.

According to the terminology used by

Ekblom

(1926, 1930) ^for

naming

the parts of thehemipterousovipositor, the dorsalplateof the second valvifer (fig. 26E, b) is the " parasternite" of the ninth segment; the small ventral plate (a) supporting the third valvula is "_sternite a " of the ninth segment; and the third valvula is

"_sterniteb " of the ninth segment.

The

shaftof the ovipositor ofPenfacorais formedof thefirstand second valvulae, the ^first being external, the second internal.

Each

firstvalvulaconsistsof a strong outer part (fig.26C,iVl) withcoarse teeth onthe upper marginof its distalpart,

and

of an inner

mem-

branous fold. Basally, as already observed, the firstvalvula is con- nected externally with the lower angle of the first valvifer (C, c),

and

mesallyby anarcuateinner

ramus

withtheloweranteriorangle of the ninthtergum (D).

The

second,orinner, valvulae (E, 2VI) are united with each other formost of their lengthby a

narrow mem-

brane between their dorsal margins;their distal parts,however, are

84 89 free,decurved,andtoothedat theirextremities. Basallyeachsecond valvulais connected by a single curved

ramus

{r2vl) with the an- teriorendofthecorrespondingsecondvalvifer.

The

secondvalvulae are

moved

back and forthbytherockingmotionof thesecondvalvi- fers on their points of articulation with the ninth tergum.

The mechanism

of thehemipterousovipositorwillbe

more

fullyexplained intheaccount of the

two

homopterousspeciestobe described.

AN

ASATRISTIS (dEGEEr)

The abdomen

of female Coreidae consists of lo segments, all of whicharevisibleanddistinct

from

above (fig.27

A),

thoughthefirst

tergumisunited withthe second.

The

sternumof thefirst segment, however, is absent (B), and the first ventral plate (//), therefore, is the second sternum. It bears laterally a pair of spiracles.

The

segments following, to the seventh, present no ^specialmodifications, andthespiraclesare located inthelateral parts oftheirventral sur- faces.

The

seventhsegmentof

Anasa

tristishas abroadtergal plate, emarginate posteriorly (A, VII).

The

seventh sternum (B, VII)

is deeply emarginate, and bears medially a pair of small lobes (a), at the bases of which is a prominent transverse groove.

The

terga of the eighth and ninth segments are distinct though

narrow

plates as seen

from

above (A, VIIIT,

IXT)

; their lateral parts appear ventrally

(B)

as

two

pairs ofmarginallobesatthesidesof thegenital region.

The

true sternal parts of these segments are coveredby a pair of large triangular plates (B, iVlf), which, as will presently beshown,are the valvifers of the eighth segment.

The

tenthsegment

(X)

projectsbeyondthegenitalsegmentsinthe

form

ofashorttube containing the anal opening.

The

description of the

abdomen

of

Anasa

tristisby

Tower

(1913)

is wholly misleading, and has been the cause of considerable con- fusiontosystematistsinHemiptera. In thefirstplace,the

numbering

of the abdominal segments asgivenby

Tower

isat faultbecausethe first segment is entirely disregarded, though ^it is represented by a distinct tergal plate (fig. 27 A, IT).

The

last pregenital segment, therefore,is segment VII, not the sixth;and the first pair of sub- genital plates (B, a) are lobes of thesternumofthissegment (VII).

The

second andlarger pair ofgenital plates (iVlf), apparently the

" eighthsternum^"ofTower,are the valvifersofthe eighth segment.

The

ventral parts of the ninth segmentare concealed, and the proc- tiger,mistakenfor theninthsegment by Tower,isthetenthsegment, numerically,thoughanatomicallyit

may

representsegments

X

and XI.

INSECT

ABDOMEN

SNODGRASS 8s

The

ovipositor of

Anasa

tristis issmall, andis ordinarily concealed beneaththe largefirstvalvifers(fig.27 B,iVlf).

When

the valvifers are spread apart, however, the lobes of the ovipositor are exposed (D),

and

betweenthe bases of the ^first pairis seen the large, open genital

chamber (GC),

^intowhich the oviduct discharges anteriorly.

The

ovipositor has the^typical hemipterous structure,exceptthat the firstvalvifers arerelatively verylarge,andthe third valvulae are ab-

vniv

Fig. 27.

—

Abdomenandovipositor ofAnasaIristis (Coreidae).

A, entireabdomen,dorsal view.

B, same, ventral view.

C,lateral view of genitalsegments, withleftwallof segment I'llremoved.

D,ventral viewof genital region,withvalvifers (iVlf) spreadapart, show- inglobes of ovipositor (iVl, 2VI), and largegenital chamber (GC) opening betweenanteriorpair.

E,leftside ofovipositorandninth tergum, withfirstvalvifersremoved,show- ing basal unionoffirstvalvula {iVl) witharm (w) ofninth tergum.

sent.

The

four lobes associatedwiththeopeningof thegenitalchamber are thefirstand second valvulae (D, iVl, 2VI).

The

firstvalvifers,as

we

haveseen,are large triangularplateslying likea pair of valves (fig. 27B, iVlf) beneath the lobes of theovi- positor. Theirbases are attached to the

membrane

^behindthe seventh segment (C) ventral to the eighthtergum.

On

the anterior margin of each valvifer is a strong

apodeme

for muscle attachments.

The

venter of the eighth segment is entirely

membranous,

and is repre-

89 sented only bythe

membranous

bridgebetween thebases of thefirst valvifers andthe firstvalvulae anterior to the openingof thegenital

chamber

(C,D,

VI

IIV).

The

firstvalvulaisa thick lobe ^(fig.27 D,E,iVl) abouttwothirds the length of thefirstvalvifer. Initsouter surfaceisaplateprovided distallywithshortspines.

The

^proximalventralangle of theplateis

prolonged as the outer

ramus

of the valvula (E, rivlo), and is attachedto the lowerbasal angle of the firstvalvifer (B, C, iVlf), thus leavingno doubtof theidentityof thelatter.

The

dorsalproximal angle of thefirst valvulaformstheinner

ramus

(E,rivli),whichis attached,inthe

manner

characteristicofHemiptera,toa process (w) fromthe ninthtergum

(IXT). The

dorsalsurface of thefirstvalvula contains

two

parallel sclerotic ridges,between which isagrooveinto whichfitsa ridgeonthe ventral surface of the corresponding second valvula.

The

secondvalviferisan oblongplate(fig.27 E,2Vlf) lying

mesad

of the ventral

arm

{n) of the ninth tergum, and articulated to the ninth tergum at a point {p) near the middle of its dorsal margin.

Its distalend has a free, truncate edge, representatives of the third valvulae being absentinAnasa, thoughthese lobes are usually present inotherHemiptera (fig. 26E,3VI).

The

second valvulae are united with each other, except at their distalends, which

form two

short free lobes (fig. 27 D, 2VI).

The

basal part of each has abroad

membranous

connectionwith the cor- responding secondvalvifer (E),andthe ventral surface bearsa strong median scleroticridge that slides in the groove of the first valvula.

The mechanism

of this ovipositor is evidently such as to cause alternateback-and-forth

movements

ofthe upperand lower valvulae

on

eachother.

The

movable articulationsof the secondvalvifers on the ninth

tergum

(fig. 27 E, />),

and

the firm unionof the firstval- vulae with the ventral

arms

{n) of the

tergum

assure an opposite

movement

inthe

two

pairs of valvulae.

The

muscles arising onthe ninthtergum and insertedon opposite ends of the second valvifers rockthe latter

up

and

down

andthus

move

the attached dorsal val- vulae; but the

same

muscles pulling on the tergum impart an op- posite

movement

to the ventral valvulae through the leverlike

arms

{11) supporting thelatter.