138 SMITHSONIAN MISCELLANEOUS

Fig. 47.

—

^{Mechanism of the sting of Apis mellifica, worker.}

A,mesal viewof right halfof stingapparatus withshaft partlydepressed, showinganteriorandposterior muscles {17, 18) of secondvalvifer, musclesof furcula (/p),and ramus muscle{20).

B, the shaft inusualposition, withramus muscle {20) contracted.

C,the shaftdepressedby contraction offurculamuscle (/p).

h,ventralarticulation offirstvalviferonsecondvalvifer;Frc, furcula; IXT,

tergal plate ofninth segment (quadrateplate);IXV,venterofninthsegment;

rivl,ramusoffirstvalvula;r2vl,ramusofsecond valvula; Stng,shaft of sting;

3VI, third valvula; 2VIJ, second^valvifer (oblong plate); a,basal articulation of shaftonramusofsecond valvula.

NO. G INSECT

ABDOMEN

SNODGRASS I39 of the

wounH

bythe shaft after the tip of the latterhas once been inserted;andincidentallythese

movements

accomplishalsotheinjec- tionof the poisonby motionof the valves of the lancetsinthepoison

chamber

of the bulb.

The

skeletal parts inthe basal apparatuscon- cerned withthe

movement

of thelancetsare thefirstand secondvalvi- fersandthequadrateplates;themotorelements are the anteriorand posteriormusclesof thesecondvalvifers.

It will be unnecessary toreview the opinions of other writers on theworkingof the

mechanism

that

moves

thestylets,sinceallinvesti- gators except Sollmann (1863) have wrongly attributed the attach-

ment

of the dorsal group of fibers of the anterior second valvifer muscles (fig.47 A,^{lya) to thefirstvalvifers,while}Sollmann onhis part,besidescommittingvarious other inaccuracies, believed the ven- tralgroupoffibers (lyb) tobe attachedonthefirstvalvifer. Hence,

alldescriptions of thesting

mechanism

contain the error ofattempting toexplain the

movements

of thelancets ascausedby musclesinserted onthefirstvalvifers. Notwithstandingthismistake,Kraepelin (1873)

isnot far

wrong

inhisaccount of theworkingofthe sting,inasmuch ashe deduces the correct

movements

of the lancets

from

hisconcept ofthemechanism.

The

only muscleinserted on the first valvifer (triangular plate) in thebee, as already shown, is the slender muscle

from

the lower marginof the spiracularplate of the eighth segment (fig. 46 D, E.

14)^;butthismuscleisattachedonthe valvifer soclose tothe posterior end of the latter, and has such a

weak

support on the spiracular plate, thatitseemsprobableitschief functionistomaintainaproper relation between those

two

sclerites.

The

principal muscles that ac- complishthe

movements

of the lancetsinthebee areundoubtedlythe large anterior andposterior muscles of the secondvalvifers (oblong plates) that have their origins on the quadrate plates of the ninth tergum (fig. 47 A, i/, 18).

The

homologues of these muscles are readily identified in all pterygote insects; in the

Hymenoptera

the fibersof thefirstmuscleareseparated into

two

distinctgroups {lya, i/b), but they areallinsertedonthe anterior

arm

of thesecondvalvi- ferorontheupper extremity^{of the}

ramus

of thesecondvalvula.

The

posteriormuscle (18)^arisesanteriorly

and

dorsallyontheinner face of thequadrateplate,anditsfibersconvergeposteriorlyandventrally to theirinsertiononthe posteriorendof the elongatesecondvalvifer.

These

two

sets ofmuscles areantagonistic to each other becausethe fulcrumof thesecond valviferon the firstvalvifer (&) ^liesbetween theirattachments on the former plate.

140 89 Inmost Otherinsectsthe secondvalvifer isarticulated directly to the ninthtergum,

and

has a simple rocking

movement

on the latter produced by the alternate contraction of its anterior and posterior muscles, because thetergum formsordinarily acompletedorsal arch over its segment andis relatively immovable. In the Hymenoptera, however, thesecondvalviferarticulateswiththefirstvalvifer, which in turnarticulates with the ninth tergum, and this interpolation of the first valvifer between the tergum and the second valvifer con- siderablychangesthe

mechanism

;butinthe bees a further modifica- tion results

from

the reduction of the ninth tergum to the pair of lateral quadrate plates whichare themselves freely movable because of their

membranous

connections with the surrounding parts.

Ob-

servationsonthe freshly extracted^stingofalivingbee

show

that the principal activity in the basal apparatus that accompanies the pro- traction and ^retraction of the lancets consists of a back-and-forth vibration of thequadrateplatesanda quick elevationanddepression of the anterior ends of the ^first valvifers (triangular plates).

The

second valvifers (oblong plates) remain relatively stationary, but there issometimesa quivering of the third valvular ^lobes.

The

working of the

mechanism

that

moves

the ^lancets will be readily understood if a cardboard model iscut out representing the skeletalparts of one-half of thestingapparatus (fig.48).

The

first valvifer of the model should beattachedbypins to thequadrateplate

and

totheoblongplate,andthelancet

must

betwisted so thatit will slideagainst theloweredgeof thestylet

when

the

two

areheld together byawireloop.

We

have observed onthelivingbee that themuscles between thequadrate tergal plate (fig. 47 A,

IXT)

and the oblong plate

{2V

_If)

move

thequadrateplateandnot theoblongplate. This

isjust the reverse of the usual interaction of thecorrespondingplates inother insects. If, therefore, thequadrateplateof themodel (fig.

48 A,

IXT)

is

moved

alternatelyinthe direction ofits

two

antagonistic muscles {17, 18), while the oblong plate (2Vlf) isheld stationary, the effectis a simpleback-and-forth

movement

of the lanceton the lower edge of the ^stylet. Hence,

when

the posterior muscle ₍₁₈₎ contracts, as

shown

at A,it

moves

thequadrate platerearward, and thelatter pullson the dorsal angle (a) of thefirstvalvifer (iVlf), with the result that the valvifer is rotated

upward

on its ventral angle (b) andretractsthe lancet (Let).

On

the other hand,

when

the anteriormuscle (ly) contracts, asat B, the quadrateplateis pulled forward and rotates the valvifer

downward,

which

movement

pro- tractsthelancet. Itispossible that the slendermuscle (A, _7^)

from

the spiracularplate to the posteriorend of thefirst valvifer

may

be anaccessory retractor of the^lancet,assupposed

by

Kraepelin.

NO. 8 INSECT

ABDOMEN

SNODGRASS 141 Because of the double articulation of the first valvifer on ^the quadrateplateandtheoblongplate (fig.48

A),

andofthe difference inlength between the

two

axes (ab and ac) of the valvifer, a very small

movement

of the quadrate plate (B, d) produces a relatively

Fig.48.—Diagrams of a model of the sting of the honey bee to show the mechanismofretractionandprotractionofthelancets.

A, the lancet retracted by contraction of ventral muscle (18) of quadrate plate (IXT) attached posteriorlyonoblongplate {sVlf).

B, the lancet protracted by contraction of dorsal muscle (//) ^of quadrate plateattached anteriorlyonoblongplate.

large

movement

of the lancet. In the living bee the motion of the quadrateplateappears asa quivering or rapidback-and-forth vibra- tion, its actual displacement being scarcely perceptible.

When

the sting isextracted, however, withthe shaftin the

wound,

themotion of thequadrateplates isgreatly increased.

VOL.

Iftheoblongplateofthemodel (fig.

48

A, 2Vlf) ^is

moved

simul- taneously with the quadrateplate, but inthe opposite direction, the effect is to protract and retract the stylet in the

same

direction as the lancet,but witheach stroke the lancet

moves

faster and farther thanthestylet. Observationsontheliving bee,however, donot

show

that this

movement

ordinarily takes place, though ^it seems entirely possible.

When

the tip of the sting of a living bee is

examined

underthe microscope,andisnotallowedtotouchanobjectitcanpenetrate,only onelancet (theleft,intheexperience of the writer) isseento

move

backand forth onthe stylet andto beprotractedbeyond the latter.

Hence,itseemsprobable that assoonasthetipof the shaftisinserted into the skin of the victim bythe

backward

swing of the basal ap- paratus, the left lancet

must

be thrust out inadvance of the ^stylet, where ^itholds its position in the

wound by means

of its barbs,

and

that then the right lancetis forcedinbeyondtheleft. Successive al- ternating thrusts of the lancets

would

thenburytheentiresting shaft deeperand deeperintheflesh inthe

manner commonly

observed.

The

force of the

backward

pullof the retractormusclesis

now

expended, notonthe retraction of the lancets, but in stretchingthe protractor muscles, which,

when

thus restored to acondition of activity, give, eachinturn,anotherthrust to thelancets.

The

motionof thelancets operates the valves attachedtothedorsalmarginsof the lancets within the cavity of the bulb of the ^shaft, and the valvesdrive the poison liquidthroughthechannelof thesting,

from

whichitissuesby

way

of the ventralcleftbetweenthedistalendsof thelancets.

ABBREVIATIONS USED ON THE FIGURES

a-a, dorso-pleural line. bv,basivalvula.

Ac, antecosta. bw,cutedgeofbodywall.

AcGl,accessory gland.

AcGlD, ductof accessory gland.

AcGlO, opening of accessory gland.

aiv, anterior intervalvula.

Am,

amnion. ^{''' '} ,

"7

Coel,coelomic sac.

An, anus.

^

. , Cx, coxa.

Ap, apodeme.

^ ^

,

/

^{, , CxC,coxa!cavity.}

' CxP, pleural coxal process.

b-b,pleuro-ventral line. D, dorsum.

bcpx,bursa copulatrix. d-2,dorsalmuscles of mesothorax.

BGl, "alkaline" gland of bee. (/:;, dorsal muscles of metathorax.

bib,bulbous basal partofunited second dil, lateral internal dorsal muscle,

valvulae. dim,medianinternaldorsalmuscle.

Bs, basisternum. ^dls,dilatormuscleof spiracle.

Cd, cardo.

Cdbl,cardioblast.

Cer,cercus.

:/,caudalfilament.

NO. 8 INSECT

ABDOMEN

SNODGRASS 143 Ecd, ectoderm.

EMsd,somatopleure of mesoderm.

Epm, epimeron.

Eppt, epiproct, eleventh abdominal tergum.

Eps, episternum.

ET, tgg tubeof ovary.

Frc,furcula.

Fu, furca, endosternum.

GC, genital chamber (bursa copula- trix).

GCls,germcells.

Gd, gonad.

gmcl, muscle ofgonapophysls.

Gon, gonapophysis.

Gpr,gonopore, ostium oviductus.

Gpr', primary median gonopore of female.

Gr}n, germarium of ovary.

Ht, heart.

I-XI, abdominal segments.

IMsd, splanchnopleure of mesoderm.

IS-XS, abdominal sterna.

IT-XIT, abdominal terga.

IXV

, venter of nintli abdominal segment.

LB,limb basis.

Let, lancet (firstvalvula).

Id,laterodorsalarea.

le, externallateral muscle.

li, internal lateral muscle.

Lsp, lamina spiracularis of eighth tergum.

Mb, intersegmental membrane.

Mcls, muscles.

Msd, mesoderm.

Odl, oviductus lateralis.

Opr, oviporus.

OS,occlusormuscleof spiracle.

Ovl, ovariole.

Ovp, shaft of ovipositor.

P, pleural, or podial, region ofbody.

Papt, paraproct.

Pcx,postcoxale.

Pdcl, ovariolepedicel.

piv,posterior intervalvula.

Ph,phragma.

pi, pleurite.

Plstn,pleurosternal plate.

PN,

postnotum.

pnvl, pons valvularum.

Proc, proctodaeum.

PsnSc, poison sac.

pt,paratergite.

Ptgr,proctiger.

ra, ramusof valvula.

rivl, ramusof firstvalvula.

rivli,innerramus of firstvalvula.

rivio,outerramusoffirstvalvula.

rsvl, ramusofsecondvalvula.

Reef,rectum.

S, definitive sternum.

Sex, subcoxa.

smel, muscles ofstylus.

Sp,spiracle.

Spr, spermathecalpore.

Spt, spermatheca.

SptD, spermathecalduct.

St,stipes.

stl,stylet(slenderdistalpartofunited second valvulae).

Stn, primitive sternum.

Stng,sting.

Sty, stylus.

NIR, neural ridge.

Od,oviduct.

Ode,definitiveoviductuscommunis.

Ode', primary rudiment of median oviduct.

T, tergum.

td, dorsaltransverse muscle.

TF,terminal filament ofovariole.

Tlpd,telopodite.

Tin,tympanum.

tv, ventral transverse muscle.

144 COLLECTIONS VOL. 89

V, venter. VI, valvula {iVl. first valvula; 2VI,

Vag,vagina. second valvula;

3V

I, third

VDph, ventral diaphragm. valvula).

ve, external ventral muscle. VU, valvifer {iVlj, first valvifer;

vi, internal ventralmuscle. ^Vlf, second valvifer).

VlllStn,sternumofeighthabdominal

VNC,

ventral nervecord.

segment(not including the first ^^>vesicle.

valvifers). ^{^•^''} vestibulum.

VIIIV, venter of eighth abdominal ^{^''"^'^ulva,} ostium vaginae.

., ,

'T'"'-

^{, , f^^wing.}

vil,lateral mternal ventral muscle.

%'im, median internal ventral muscle.

Y

,yolk.