124 SMITHSONIAN MISCELLANEOUS COLLECTIONS

(fig,41, 2VI) issometimescalledthe sheath of the sting (Cheshire, 1886, Snodgrass 1910, 1925), or the shaft (Betts, 1923)^{;but, since} thispartishollowed beneathto

form

a channel giving passagetothe poison,

European

writersgenerallytermitthestingtrough,or gutter (Stachelrinne, fourrou-guttlere).

The

enlarged basal part of this organisthe bulb {bib);the slender taperingdistalpart

we may

term thestylet (stl).

The

third valvulae (figs.40,41,jVl)aresometimes calledthe "palpi "of thesting,but sincetheirchief functionis,asin otherHymenoptera,toensheaththedistalpart of thestingor oviposi- torshaft, they are bettertermedthe sheath lobes (Stachelscheiden)

The

general structure of thebee'ssting differsbutlittle

from

that of the ovipositor of otherHymenoptera, andit isonlyincertain de-

FiG.41.

—

The sting and associated parts of Apis meHifica, worker. (From Snodgrass, 1910,butrelettered inaccord with the general nomenclature ofthe ovipositor adoptedin thispaper.)

tails thatthe sting is specialized for its specific function of ejecting thepoison liquid

from

the reservoir of the poison gland.

The

spiracularplates of the eighth tergumoverlap externally the upper ends of the lateral platesof the ninth

tergum

(fig. 40).

The

spiracular plates of the worker are triangular in shape (fig. 43B, Lsp), withthe loweranteriorangle ofeachproduced intoa process for muscle attachment. In thequeen the plates are relatively larger and of irregular

form

(fig. 44 C).

Though

the spiracular platesare connected entirely by

membrane

with the surrounding parts, they have anelaborate musculature, which will be fully described later, butitshould benoted particularly thatthey are anchoredinposition bydorsalmuscles

from

the seventh

tergum

andventralmuscles

from

the seventhsternum (fig. 43 B).

On

theotherhand,each spiracular plateisconnected withthe ninthtergal plateof the

same

sidebytwo

NO. O INSECT

ABDOMEN

SNODGRASS 125 muscles (lo, ii)

from

its upper end, and with thefirst valvifer by asinglemuscle ₍₁₄₎

from

itslower margin.

The

quadrateplates, or lateraltergal scleritesof the ninth

dorsum

(fig. 41,

IXT),

are the suspensory plates of the sting mechanism.

Becauseoftheir

membranous

dorsalconnectionsthey are freely

mova-

bleontheirupperangles (/) within the overlapping spiracular^plates.

Each

quadrateplateisa large four-sidedsclerite,articulatedanteriorly withthe dorsal posterior angle (a) of the firstvalvifer (iVlf). Its dorsalpart projectsintothe

body

cavity asa flatapodemalextension

(Ap)

on which important muscles of the sting

mechanism

are at- tached;itsloweredgeoverlaps thesecondvalvifer_{2'Vlf),withwhich

itisconnectedbya

membranous

foldof theintegument.

The

triangularplate,orfirstvalvifer (fig.41, iVlf),isarelatively small sclerite lyinganteriorto thequadrateplate. Its anterior angle (c) iscontinuouswiththe upperend of the

ramus

of thelancet, or firstvalvula (rivl),

and

itsposteriorangles {a, b) articulate respec- tively withthe anterior angle of the quadrateplate

(IXT)

and the dorsal marginof the second valvifer, or oblong plate {2Vlf).

The

single muscle of thefirstvalvifer, whicharises onthe lower margin of the spiracularplate (fig.43B, 14),^isinsertedontheupper edgeof the valvifervery nearthe posterior dorsal angle (fig. 42 A, 14). In the usual position themuscleis horizontal.

The

oblong plate, or secondvalvifer (fig. 41, 2Vlf), ^liesbeneath the first valvifer

and

the quadrate plate. Its articulation with the lower posteriorangle of the first valvifer {b) is

somewhat

before themiddleofitsdorsalmargin. Itsanteriorendisnarrowed andcon- tinuous with the

ramus

of the second valvula {2rvl); posteriorly it

supports the third valvula (jF/), whichin the bee is a short, soft, mostly

membranous

appendage.

The

oblong plates of opposite sides are connected medially by an ample

membrane

thickly clothed with hairs, which represents the venter of the ninthsegment.

The membrane

isordinarilyarchedup-

ward

abovethebase of the sting (fig.45 A,

IXV),

forming below^ita deepcavityinwhichthebulb of thestingisensheathed,but,

when

the sting is depressed, the

membrane

^is partly everted and appears asa hairypad overthebulb (fig.41,

IXV).

The

shaft of the sting is

composed

of the unitedsecond valvulae (fig. 41, 2VI), and of the slender first valvulae, or lancets {iVl).

The

single dorsal piece,

formed

of the secondvalvulae, is enlarged basally as thebulb of the sting {bib); its distaltapering partis the stylet {stl).

The

lancets slide freely onthe lateral ventral margins of the bulb

and

stylet (fig. 42

E)

_;their loweredges arein contact.

COLLECTIONS VOL. 89 and between the three parts of the shaft is the poison canal of the sting (r). In the bulb the canalexpandstoa largechamber,inwhich

liea pair of pouchlike valvesborne ontheupper edges of the lancets (A, Vlv) that serve to drive the poison liquid through the canal,

from

which^it

makes

itsexitnear thetipofthe sting

from

aventral cleft between the lancets.

The

stings of the worker and thequeen differprincipallyinthe sizeand

form

of theshaft.

The

shaft of the queenisrelativelylarger

and

isstrongly bent

downward

inthe region of the bulb;

when

exserted, therefore,itcurves ventrally or anteriorly accordingto the position of theabdomen.

The

poison sac opensdi- rectly into thebase of the bulb (fig. 42C, PsnSc).

The

distal end of thestylet is

narrow

but rounded, and inthe workerithas three pairsof very small lateral barbs on its dorsal surface.

The

tips of thelancetsareacute,andtheterminal part of eachlancetoftheworker

is strongly serrate ventrally on its outer surface

by

a series of 10 retrorse barbs.

The

shaft of the stingis supported atits baseon the rami of the valvulae (fig. 41, rivl, r2vl).

The two

pairs of rami are widely divergent as theycurve

upward

to theirconnectionswiththe valvifers {iVlf,^Vlf).

A membrane

stretchesbetweenthe ramiof thesecond valvulae.

The two

ramiofeachsideareunitedbyagroove-and-ridge connection continuous with that on the shaft (fig. 42 E), but since the

ramus

of the first valvula lies against the outer surface of the

ramus

of thesecondvalvula (fig.41), thegrooveofthefirstvalvula, which follows the dorsaledge of thelancet (fig.42 A, d),goes over tothe inner face of the

ramus

{d').

Inorderto understand an importantpointinthe

mechanism

of the sting it willbe necessaryto give closeattentionto certain detailsof structureatthebase of thebulb.

Each

secondvalvular

ramus

israther broad (fig. 42B, r2vl) and presents a rounded lobe

(w)

near its

lowerend.

The

direct unionof the

ramus

withthebulbis a

narrow

sclerotic bar {x), but laterad of ^it a hookedprocess {y)

from

the base of the bulb

makes

averyfineconnection {s) withthe lobe

(w)

of the ramus.

The

muscle of the

ramus

{20) is inserted on this process.

The

basal surface of the bulb is inclined forwardconsiderably in advanceofitsconnectionswiththerami (fig.42 C), anda

membran-

ous foldprojects

from

it dorsally intothebody cavity. Inthis fold thereliesaY-shapedrod,thefurcula (C, Frc,

D),

the

arms

ofwhich areconnected withthebase of thebulb,while themedian stemcurves

upward

andposteriorly above thelatter, and abovethe

membranous

ninthventer

(IXV). Upon

the furcula are inserteda pair of large