62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89

5. Tergal muscles of the anterior intervalvida ^(fig. 17 E,

H). —

A

slendermuscleoneachsidearisingonanteriormarginoflateralpart of ninthtergum;the

two

converging ventrally to insertions medially onanterior intervalvula (aiv).

6. Anteriortergalmusclesofsecondvalvifers (fig. 17 E, G,

H).

—

A

pair of largeverticalmuscles, arising onanteriorlateral

apodemes

ofninthtergum,internal to5^{;insertionsventral}onanterior processes (inferiorapophyses) ofsecondvalvifers (G,

H).

7. Posteriortergalmusclesofsecondvalvifers (fig. 17 E, G,

H).

—

A

pair of large, flat, horizontal muscles; each arising anteriorly on anterior margin of ninth

tergum (H),

external to 6

(E)

; inserted posteriorlyonposterior dorsal

apodeme

(superior apophysis) ofsec- ond^valvifer (E, G,

H,

i).

8. Tergalmusclesof posterior intervalvula ^(fig.17 E,

H). — A

pair ofrelativelyslender muscles, arisingonlateralparts of ninth tergum

(E)

above 5 and ^{external to} upper ends of 6; extend ventrally and posteriorly,ectad of7,toinsertionsin

membranes

lateradof posterior intervalvula (E,

H,

piv), with a few fibers attached on the latter.

The

next

two

pairs ofmuscleshavea ventral positionandconnect the valviferswiththe posteriorintervalvula, buttheir

homology

with muscles of the pregenitalsegments isnot clear.

They

are described by

Ford

(1923) as primaryand secondary ^"outer sternalmuscles"

of the ninthsegment.

An

^"inner sternalmuscle

"of

the ninth seg- ment, she says,extends

from

the firstvalvifer to the paraproct, but the writer didnot observethismuscleinthefemaleof Gryllus, which, according to

Du

Porte (1920), occurs in the maleonly.

9. Intervalvidar muscles _{of the} first valvifers (fig.

17E, H). —

A

pair of short, thick, cylindrical muscles arising on sides of median

apodeme

(^) of posterior intervalvula {piv)^;extending laterallyand alittleforwardtoposteriorinternalapodemesoffirstvalvifers(H,/).

10. Intervalvular muscles _of second valvifers (fig.

17E, H).

—

Origins medially on

apodeme

of posterior intervalvula {k), ventral to p; diverge anteriorly to insertions on anterior ends of second valvifers.

Musclespertainingtotherudimentarysecond, orinner,valvulae the writer did not find in Gryllus, but

Ford

(1923) describes a pair of suchmuscles havingtheiroriginsonthe anterior intervalvulaandtheir insertions inthetipsof inner valvulae. In Scuddcriathe well-devel- oped muscles of the inner valvulae have their origins on the inner faces of the secondvalvifers.

The mechanism

of the ovipositor.

— The

eggs of Gryllus are laid intheground. Beforeinserting the ovipositor thefemaleoftenclears

INSECT

ABDOMEN

SNODGRASS 63 a small space on the.surface of the earth selected as the oviposition site.

The

clearing operationis a strenuouslyperformed task,the in- secthurriedly scratching

away

loose surface material with her fore feetasifindesperate haste topreparethespot,

from

whichshe

may

remove in her jaws pellets and pebbles as large as her body. This done, she reverses her position andjabs the ovipositor atthe clear- ing,or, at least,such isher evident intent, but oftenas not theaim miscarries, quiteunperceivedbytheimpetuouscricket,andthe subse- quentinsertion of the ovipositor isthen

made

at a placeentirelyun- touchedinthe

work

of preparation.

At

thebeginningof oviposition the Gryllus femaleelevates herself

on

her hind legs, thus raising the abdomen, and depresses the ovi- positoruntilitsshaftisdirected posteriorlyand

downward

atanangle ofabout 45^degreestothe surface of theground,as thetipisinserted

-.^Vl

-iVl

Fig.20.

—

^Sectionsof theshaft ofthe ovipositorofGryllusassiiiiilis,showing groove-and-ridge connectionsbetweenthe firstandthirdvalvulae.

intothe latter. Withinthe space of a minute,

when

working insoft soil, the ovipositorisburied to full length,and the terminal part of the

abdomen

comesincontactwith theground. Duringthe insertion process the

two

valvulae of eachside glide rapidlyback and forth a short distance on each other, the corresponding blades of opposite sidesapparentlyworkinginunison.

The

egg^entersthe channelof the ovipositoratthe bases of the valvulae, passesalong theentire length of theshaft,andisextruded

from

thetipintothebottomofthe ex- cavation.

During

the withdrawal of the ovipositor,the organis re- peatedly thrust

down

into the cavity at successively shorter depths, evidentlyto packthesoilabovethe egg.

When

the ovipositor is fully extracted, theinsectgivesnofurther attentiontotheplacewherethe egghas been intrusted to theearth. These observations on Gryllus were

made

on individuals in confinement.

Ncmohius

scratches over the surface

where

the egg has been deposited before leaving ^it

;

Oecanthusplugseacheggcavityshe

makes

inatwigwithbark chew-

64 89 ings

mixed

with a gluey discharge

from

the pvipositor.

As

is the usual habitwithcrickets, Gryllns depositsbutoneeggineach boring.

The movements

of the ovipositor

made

by Gryllus during egg laying in soft soil are thus seen to be very simple ones, and there

is scarcely any accompanying motion of the abdomen, such as the contortions

made

by Oecanthus while drilling into wood.

The

ovi- positor of Gryllus is lowered preparatory to its insertion into the ground, its penetration is accompanied by the rapid back-and-forth

movement

of the valvulae

on

each other, and after withdrawal it is elevated againto the usual position,

The

entire organ is probably capable of aslightprotraction

and

retraction.

The

fixedpoints of

movement

inthe basal parts of the ovipositor are thearticulationsof thefirstvalviferswiththeloweredges of the ninth abdominal

tergum

(fig. 17A,F, 21, a), the outer and inner articulationsof the two valvifers on each sidewith each other (fig.

17A, b,fig. 21, dh), andthe weak, flexibleunions of the first val- vulae with the lower angles of the first valvifers (c). Otherwise the ovipositor has a free

movement

onthe

abdomen

by

means

of its

membranous

connectionswiththe^latter.

The movements

ofdepressionandelevation ofthe ovipositoraffect not only the shaft but the entire basal parts of the organ,

and

the fulcraare thearticulationsof thefirstvalviferswiththelowerangles of the ninth tergum (figs. 17A, 21, a).

The

muscles that accom- plish these

movements

are clearly the anterior and posterior lateral muscles of the ninth tergum ^(figs. 17 E,

H,

21, 5, 8), the first of which are inserted ventrally on the anterior intervalvula (aiv), the second on or near the posterior intervalvula (piv).

The

^insertion points of thesemusclesare anteriorandposteriortothearticulations of the firstvalvifers onthe ninth tergum (a), and pulling

upward on

these points correspondingly depresses or elevates the ovipositor.

Morphologicallythe levatorsanddepressors of the ovipositor are the tergosternalmusclesof the ninthabdominalsegment.

The

alternating opposite

movements

of the dorsal and ventral valvulaeon each other depend on the articulation of the first val- viferswiththe ninth tergum (fig. 21, a), and on theinner articula- tionof the two valvifers of each sidewith each other (dh).

A

de- pression of the posterior end of either of the first valvifers

(B)

causes thecorrespondingventral valvula,whichisflexiblyattachedto the ventral angle of the first valvifer, to slide proximally on the lower edgeofthe dorsalvalvula. But,sincethefirstvalviferrockson the fulcrum (a) of the ninth tergum, its posterior end,

when

de- pressed, describes a short arc of a circle in a

downward

direction

NO. 8 INSECT

ABDOMEN

SNODGRASS 65 (indicated by the curved arrow on the right), and this

movement

bears

down

on the second valvifer andgives this valvifer a thrust posteriorly,whichcauses the dorsal valvulato slide

backward

onthe ventral valvula while the latter is

moving

forward.

The

opposite

movement

of the first valvifer (indicated by the curved arrow on theleft) reverses the

movement

of the valvulaeoneachother. Thus, by a simple rocking motion of the first valvifer

on

its articulation withthe ninthtergum,the

two

valvulae of the

same

side

move

length- wiseoneach other alternatelyin oppositedirections. This actioncan easily bedemonstrated ona dissected specimen.

But

also itwill be observed that a rockingmotion of the secondvalvifer onits articu- lation with the first valvifer (dh) imparts the

same movements

to

iVlf

A

^{2Vlf iVl}

Fig.21.—Diagrams of the basal mechanism of the ovipositor of Gryllus assimilis.

a,articulationof firstvalviferwith ninthtergum; aiv,anterior intervalvula

;

c, attachrnent of ^first valvula to first valvifer; dh, inner articulation between

first and second valvifers; e, anterior apodeme of first valvifer; /, posterior apodemeof firstvalvifer; g,anterior apodeme of second valvifer; i,posterior apodemeofsecond valvifer; k, median apodemeofposterior intervalvula; piv, posterior intervalvula; iVl,firstvalvula;3VI, third valvula; iVlf,firstvalvifer;

2Vlf, secondvalvifer.

the

two

valvulae,andincreases the degreeof

movement

inthe dorsal valvula.

The mechanism

is extremelydelicate,

and

theleast motion, either of the first valvifers on the ninth tergum, or of the second valviferson thefirstvalvifers,producesthe sliding

movement

of the valvulae on eachother.

The

dorsal valvulae are the stronger of the

two

pairs of blades formingthe shaft of the ovipositor,

and

endin sharppointswhich normallyprojectbeyondthethin,truncatetipsof thesecondvalvulae (fig. 17 B,C).

The

musclesthatbringaboutthe

movement

of the valvulaeoneach other are the three pairs of large lateral muscles inserted on the valvifers (fig.

17E, H,

_{j, 6, /).} Thesemuscles, morphologically, are thetergopleuralmusclesof the eighthandninthabdominalsegments.

The

^firstoneachside (3), arisingontheeighthtergum andinserted

89 onthe anteriorend of the firstvalvifer,depresses the posterior end ofthisvalviferby puUing

upward

onitsanteriorend (fig.21A, B).

The

muscie,however,hasnoantagonist insertedonthefirstvalvifer, so that its contraction simply retracts the ventral valvula and pro- tracts thedorsal valvula (B). Afterthis,the principal

movement

of the valvulae on each other evidently results

from

themotion of the secondvalvifer on thefirst, andtherecanbe no doubt thatthe

mus-

cles effecting this action are those of the ninthtergum inserted on the second valvifers (fig. 17 E, G,

H,

6, 7).

The

first of these

two

muscles (d) isattachedonthe anteriorapophysis _(g) of the second valvifer; the second _(7), having a horizontal position, is attached on the posterior dorsal

arm

(i) of the

same

valvifer.

The two mus-

cles thusoppose each other

from

opposite sidesof the articular sur- face (G, h) by whichthe secondvalvifer rockson thefirstvalvifer.

If the ovipositor were a rigid structure, this

mechanism

apparently could only

move

the distal shaft of the ovipositor

up

and

down

on the fulcral point (h), but as already noted, the demonstrable effect of therocking of thesecondvalviferonthe^firstvalviferisanopposite back-and-forth

movement

of the

two

valvulae of the

same

side on eachother.

The two

pairs of ventral muscles of the ovipositor (fig. 17 E. H.

c), 10) uniting the first valvifers and the second valvifers, respec- tively,withthe posterior intervalvula{p'lv),mustbe tensorsin func- tion,since theircontraction could onlyproduce acompressionof the basal parts of the ovipositor.

The

muscles of the seventh sternum

(fig. 19A, 7), inserted on the anterior ends of the first valvifers (fig. 17A,E, F,

H,

i),are evidently retractors of theovipositor.

During

oviposition, theeggpassesthroughtheentire length of the ovipositor in the channel betweenthe valvulae. It appears that the

movement

of the valvulaeoneach other isthe cause of the progress of the egg, butitisnot evident

how

theeffectisproduced, sincethe innersurfaces of the valvulae aresmooth andgive no suggestion of the

means

by whichthe

movement

of the&gg^iscontrolled.

The

distal end of the ovipositor is

somewhat

enlargedand forms a lanceheadlike termination of the shaftwiththe acute apexslightly depressed (fig.17B).

The

tipsof thevalvulae arecapable ofopening

upon

each other by reason of a hingelike

membranous

area

(m)

atthebase of the enlarged terminal part of each of the dorsalvalvulae.

In handling narcotized specimens, the observer

may

be surprised to seetheendsof thevalvulae suddenlygape widelyapart (D),asthey sometimes do. There are no muscles in the terminal parts of the ovipositor;the openingof thedistalextremities of the bladesis pro-

NO. 8 INSECT

ABDOMEN

SNODGRASS 67 duced automaticallyby an extreme retraction of the dorsal valvulae, whichbrings a pair of knobs (C, n) ontheir undersurfaces against abruptly rising areas onthe upper surfaces of the ventral valvulae, with theresultthatthedistalparts ofthedorsal valvulae, beyondthe

membranous

hinges (in) at their bases, are suddenlythrown

upward

(D).

The

opening apparatus probablyenables thecricket to hold the egginthetip of the ovipositorsothat it

may

be thrust securely into thebottomof the hole

where

itisdeposited. Thisuse of the ovipositor thewriter has clearly observed in thecase of

Nemohius

ovipositing against the wallof a glassjar.

The

postgenitalsegments.

—

^The tenthandeleventhsegmentsof the

abdomen

together

form

a conical end piece of thebody, which sup- ports the cerci laterally and encloses the anus between its distal lobes (fig. 22

A).

The

tenthtergum andtheepiproct(fig.22A,

XT,

Eppt) are united inacomposite supra-analplate,but the boundaryseparating the

two component

partsof theplateisquite evident.

The

narrowedanterior lateral angles of the dorsal part of the tenth tergum are continued intoabruptly widenedlateral plates (fig. 18, p), whichare produced ventrally on thesides of the tenthsegment, before the bases of the cerci, to the lower angles of the paraprocts (Papt).

The

venter of the tenth segment is mostly

membranous,

but it contains a narrow, transversely elongate sternal sclerotization (fig. 22C,

XStn).

In- ternallythe anteriormargin of the tenthtergumisstrengthenedby^a strong antecosta (Ac).

The

dorsal partof the tenthtergumis sepa- rated

from

the base of the cercus on each side

by

a wide

mem-

branousareacontaining a small crescenticsclerite (A,_q).

The

tergum of the eleventh segment, or epiproct, consists of the distal lobe of the supra-anal plate (fig. 22A, Eppt). Its marginal parts (s) are separated

from

the median shield-shaped region bya narrow, weakly sclerotized or

membranous

area oneach side.

The

marginal

band

(s) appears to endanteriorlyatthe transverse folds extending outward

from

the posterior edge of the tenth tergum to the bases of the cerci. Considering, however, that the cerci belong to the eleventh segment,

and

observing that in Scudderia (fig. 12) the basal angles of the epiproct (Eppt) are produced into slender arms extending forward

and downward

anterior to thebases of the cerci,thereisreasontobelievethatthemarginal bandof the epiproct inGryllusismorphologicallycontinuedanteriorlyinthenarrowcres- centic sclerites (fig. 22A, q) lying

mesad

of the bases of the cerci, which appear to belong to the

dorsum

of the tenth segment.

When

the area about the base of the cercus is stretched and flattened out

(B), thereis brought to viewaweaklyscleroticconnection between thesclerites.yand q,and,moreover,there isexposeda distinct third sclerite (r) interveningbetweenqandthe base of the cercus

{LB),

which by ananterior processarticulateswiththeinnermarginof the

Fig. 22.

—

StructureofpostgenitalsegmentsofGryllnsassimilis,andmuscles of cerci ofHeterojapyxgallardi.

A,dorsalviewofpostgenital segmentsofGryllns.

B, right half of same with membranous parts stretched to show hidden sclerites.

C, musclesof right half ofpostgenitalsegmentsofGryllns.

D,cerci andmuscles intenthsegmentofHeterojapyx.

latter. It isto be seen, therefore, that a broken scleroticcontinuity existsbetweenthebase of the cercusandtheepiproct.

The

paraprocts (figs. 18, 22 A,B, C, Papt) are large, half-oval sclerites occupying the ventrolateral parts of the eleventh segment

NO. 8 INSECT

ABDOMEN

SNODGRASS 69 behind and below the bases of the cerci and the lower ends of the lateralplatesof the tenth tergum (fig. i8).

The

dorsaledges of the paraprocts areconnectedby

membrane

withthelateralmarginsof the epiproct (fig.22A, C), andtheirlower edgesareunitedtoeach other byamedianventral

membrane,

the posterioredge ofwhich forms a small medianflap, or hypoproct (C, Hypt).

The

posterior margins of the several lobes of the eleventhsegmentare inflected in the cir- cumanal

membrane,

whichispossiblytobe regardedasaremnantof the periproct, and which is directly continued into the walls of the rectum.

The

cerciareimplantedon

membranous

areas (fig. 18) surrounded by the laterodorsal crescentic sclerites {q) above, the lateral plates {p) of the tenthtergumanteriorly

and

ventrally, andtheparaprocts (Papt) behind.

Each

cercus has a distinctthough narrow annular basis (fig. 22B,

LB),

which, asalready observed, articulatesby its inner margin with the anterior

arm

of the small oval sclerite (r) attached to the posterior end of the crescentic dorsal sclerite (q).

The

appendage is provided with six muscles arising on the tenth tergum (C).

The

musculatureofthe postgenital segments haslittle resemblance tothat of the genital andvisceralsegments andgives little evidence bearingon the

morphology

of the terminal parts of the abdomen.

The

tenth segment muscles are mostly inserted on thebases of the cerci;themuscles of the eleventh segment connect the epiproct and paraprocts, and go to the circumanal

membrane. The

postgenital complexismovable ontherestof the

abdomen

bythe dorsalmuscles of the ninth segmentinsertedon the antecosta of the tenthtergum, andin the malethere isa strong ventral muscle oneach side

from

the anteriorlateral angle of the ninth sternum to the inner face of theparaproct.

The

muscles arising on the tenth tergum include the muscles of the cerci,

two

pairs of rectal muscles, and a pair of muscles to the paraproct.

Du

Porte (1920) describesandfiguresforGrylliisa dorsal longitudinalmusclelying "nearthemedianlineofthe suranalplate, stretching

from

theanteriortothe posteriorbordersof thesclerite"

;

but the writer couldfindno such musclepresent,and no corresponding muscleismentioned by

Ford

(1923).

The

musclesof the tenth and eleventh segments, illustrated at

C

of Figure 22, are the following:

II.

— A

broad,flat,transversemusclearising mediallyontenthter-

gum

;insertedonanterior

arm

of the smallsclerite (B,r) articulating with dorsal margin of base of cercus.