NO. 13 STAPH YLINIDAE BLACK WELDER 75

Fig. 26.

—

Detailsof thestructure ofthelegs.

A, musculatureof themiddleleg ofThbiopinuspictusLee. B,trochantero- femoral jointofposterior leg ofBolitobius cinctus (Grav.). C, posteriorcoxa ofOxytclnsscnlptnsGrav. D, posteriorcoxaofErchomnsventricidus (Say).

E,group of setaefrom anteriortibiaof Blediusmonstratus Csy. F, posterior coxaofPacdenislactusEr. G, posteriorcoxaofStenusscidptilisCsy. H,pos- teriorcoxaofHypocyptusloniiicoDUS (Payk.). I, groupofsetaefrom middle co.xaofTachinusliiid^atusMels. _J,anteriortibiaofLathrotropis jacobina(Lee).

K,posterior coxaofHabrocerus schzvarziHorn. L,group ofsetaeon middle trochanterofProtcinnslimbattisMakl.

94

situation is frequently very different on different legs of the

same

specimen, but the one

from

the

same

thoracic segment of different speciescanbecompared.

The

present subfamily classification of the Staphylinidae is based largely on the shape of the posterior coxae. These segments are classifiedas globose,conical, triangular,or transverse, anda distinc- tionisoftenattemptedbetween coxaethat attainthe pleural pieces of themetasternumandthosethatdonot.

Inallthe species studied,

and

indeed almostnecessarily so

from

a functional viewpoint, the posterior coxae have articulations in

two

places. Morphologically the

more

important of these is the pleural articulationwhichis situatedatthelateralextremity of thecoxaand at the posterior end of the metathoracic pleurites. This is the most fundamentalpoint inthe coxal areaandthe articulation isprobably neverlost.

The

coxahasalsoasecondarticulation with thesternum, usuallynearthe midline. Frequentlythelateralpartsof thecoxaare covered bythe sternum and are

more

or less invisible

from

the ex- terior. It is, then, the exposed portion whichhas given rise to the aboveclassification,but obviouslythisisnotafundamentalseparation.

The

differences between coxaethat are " small andglobose^" (fig.

26 G), those that are conical (fig. 26 F), those that are triangular (fig.26

K),

andthose that are transverse ^(fig.26C,D,

H)

aremat- ters of degree and

form

a continuous series. It should be possible to find a

more

consistent

and

fundamental characterto express the apparentdifferences.

There seemtobe three distincttypes of coxalstructure. In

many

species the coxa is conical or triangular without expansionsbeyond thelinesconnecting the three articulations. In others thesideof the coxais expandedlaterallyandcaudallyintoaplatewhich liesunder- neath the femur and below (dorsad) the level of the sternum. In thethirdgroupthereisan upperlamellaof thecoxawhichisexpanded laterally and posteriorly into aplate which is nearly atthe level of the sternum and completely covers the lower portion of the coxa.

Thesethree are the onlymorphologicaltypes recognized.

The

following speciesbelongtothefirstgroup,havingthecoxanot expanded laterally and caudally: Osorlus, Stenus (fig. 26 G), the Paederinae (fig.26 F),the Staphylininae,andpossiblyLiparocepha-

lus. These are the ones generally saidto have the coxaeconical or triangular.

The

second group, thosehavingthe coxae expanded laterally and caudally into a platethat is partly covered bythe

femur

in repose, frequently also have a slight expansion over the base of the tro-

NO. 13

STAPH

YLINIDAE

— BLACK WELDER

_'J'J chanter but not extended laterally. It includes Micropeplus, the Omaliinae,alltheOxytelinaeexcept Osor'ms,

Hypocyptus

(fig.26

H),

Tachyporiis, Tachinns,Erchomtis (fig. 26

D),

Bolitohius,andall the Aleocharinae except possibly Liparocephalus. These are chiefly the forms said tohavethecoxaetransverse.

The

^thirdgroupcontains onlyHabrocerus (fig. 26

K). The

coxa

is rather triangular,but the upper surface is broadly expandedinto a lamellawhichcovers part of the

femur

inreposeand extendslaterally clear tothe pleuralarticulation.

Micropeplus appearstobedistinct

from

alltheothersinthe presence ofa

narrow

separatestripextending

from

the trochanteralarticulation to the pleural one. It

may

bea secondary separation

from

the coxa butisentirelyunique.

THE ABDOMEN

The abdomen

of Staphylinidae is

composed

of 10 segments in all the species studied. Inallcases thefirst segmentisrepresentedonly bythetergiteandrarelya paratergiteon eachsidebehindthespiracle

{^g.gA,ptt.i).

The

second segment

may

beentirely

membranous,

asisapparently thecasewith Micropeplus. It

may

be representedbyatergite alone, asin Trigonurus,Phloeocharis, Osorius, Stenus, Gastrolohium,

Hes-

perobimn,Paederillus, Paederus,Lathrotropis, Hypocyptus, Liparo- cephalus,Xenodusa, Lorinota, Aleochara, and

Baryodma. A

^pair of small paratergitesispresentatthesides inGeodromicus, Tanyrhimts, Lathriiuacum,Pseudopsis, Creophilus (fig.9

A)

andall the Staphy-

linini, Glenus,Acylophorus, Quedius,Oxyporus, Habrocerus, Tachy- porus, Tachinns,

Erchomus,

Bolitobius, and possibly Oligota. Be- sides these sclerites the following also have

some

sclerotization of the sternite: Pelccomalium, Proteinus, Eumalus, Xantholinus, and possiblyMetoponcus.

The

greatestdevelopmentofthissegment,

how-

ever, is inthe tribeOxytelini.

The

speciesof this tribe haveall the scleritescompletely developed so as toappearidentical withthe suc- ceeding segmentsin structure.

The

third, fourth, fifth, sixth, and seventh segments are very similar in structure.

They

each have a normal tergite and sternite andusuallyoneor

two

paratergitesoneachside.

Only

Leptochirus, Eumalus, and Osorius are entirely without paratergites, and the followinghaveonlyoneon eachside: Micropeplus,alltheOmaliinae

(fig.27

D),

Proteinus,Trigonurus,Phloeocharis, Pseudopsis, Stenus, and Habrocerus. All theother speciesexamined have

two

paratergites

78 94 oneachsideof thesegments

from

threeto seven. Figure

9 A

shows thenormal

form

of these sclerites. Modifications arechiefly in size, distinctness of the sutures, and vestiture.

Xenodusa

has the para- tergites modified to

form

the hairy lobes or trichomes (fig. 27

B)

whichproject over the succeeding segment.

vt^JL^MJm^

Fig. 27.

—

Detailsof thestructureoftheabdomen, andthe intrafamily variationinthe patternoftheintersegmentalmembranes.

A,ventralaspectofabdomenofGastrolohiumbicolor (Grav.). B, paratergites andtrichomeofXenodusasharpiWasm. C, patternofintersegmentalmembrane

ofLathrotropis jacobina(Lee). D, paratergiteofGeodromicus brnnncus(Say).

E, pattern ofPacdcruslactusEr. F,groupofsetae fromsternite ofBoHtobius cinctns (Grav.); G, patternofXantholinus picipcnnis Lee. H,patternofStenus scidptilis Csy. I, posterior margin of sixth tergite of Acylophorns flavicollis Sachse. J, patternofOsorins mundiis Shp.

The membranes

between these intermediate segments are usually

marked

ina definitepatternwithminute spotsof regular shape and deepercolor.

They

appeartobe actualsclerotizations inthe

membrane.

These patterns are fairly constant inthe various groups.

The

most frequent pattern is one of small rectangular areas arranged either in transverse or in longitudinal rows or both, often changing

from

NO. 13

STAPH

YLINIDAE

BLACK WELDER

₇₉ onetotheotherinasingle

membrane

(fig.27C,E). Thispatternis

found onMicropepliis,alltheOmaliinae,allthePaederinae,Oxyporus, andBolitohins.

Two

specieshaveadefinitelyhexagonalpattern (fig.27

H). They

are Leptochirus and Stenus. In Eumalns, Pseiidopsis, and Osorius

(fig. 27_J) theareas are very small and angularin shape and grade intoelongate transverse pieces near the edges of the

membrane.

The

subfamily Staphylininae is characterized

by

a pattern of ir- regular-sizedareas arrangedinlongitudinalbands separatedbyclear

membrane

(fig.

9F).

Xantholinns and Mefoponciisdiffer

somewhat

in having the areas strongly angular and frequently triangular or lozenge-shaped. Acylophorus is

more

or less intermediate between theseandthetypical

form

for the subfamily, andQuediusis

marked

only with longitudinal rows of very small spots.

Oxytehis and Bledhis havea patternverysimilartothat

shown

in figure9

H

exceptthatthebands runtransversely. InAploderus and Platystethus thereisnoactual pattern,as theminutedotsappear like an even stipple.

In

some

the

membranes

appearperfectlycleareven undera fairly high magnification. Theseinclude Proteinus, Trigonuriis,Habrocerus, Hypocyptus, Tachyporus,Tachinus, Erchomiis,andalltheAleochari- nae studied.

Variousmodifications of

form

and vestiture are found ontheab- domen, but these are notveryconstantandare frequently modifica- tions of only one sex.

The

large posterior lobes on the fifth seg-

ment

of certain males of Gastrolohium (fig. 27

A)

and the circular or crescentic groupsof setae andpores onthe

same

species are ex- amplesof sexual modifications. These groupsof setae (fig.27 A, x) are called foveae intheliterature and consistof acircle or band of setae set in moderate sockets and completelysurrounded by a large

number

of poreswhich give avery rough appearance tothe surface.

The

discal setae of BoUtohius (fig. 27

F)

do not have a definite socket but are set intotheapex of a U-shaped area

marked

only by afine lineonthe surface.

The

posteriormargins of the intermediate segmentsofAcylophorus(fig.27I)arecrenulatewiththe depressions

much

deeperon the ectal surface than onthe ental.

A

rather large seta is set at the anterior end of each depression.

The

eighth segmentis

composed

of only a tergite and a sternite.

The

tergite bears a spiracle similarlyto the preceding segments and generallyis narrower andrather strongly tapering.

The

eighth seg-

ment

isusually considered tobepart of thegenitalia. Inthe case of thefemaleit istherefore treated inthat connection,butin themales

8o 94

it is

more

convenient to restrict the discussion of the " genitaha^"

to the consideration of thegenital tube or aedeagu's alone.

For

this reason the eighth andninth segments of themales willbe discussed brieflyhere.

The

posteriorborderof the eighthsegmentis frequently modified inthemale. Thismodification

may

take the

form

oflobation, emar- gination orincisure, abnormalvestiture or sculpture, etc. It is gen- erallythe lastvisible segment of theabdomen, though ^it

may

be so farretractedv^^ithinthepreceding segmentsastobeinvisible.

The

ninth segment is represented

by

atergite, asternite, and tv^o small lateralplates bearing the valvulae orgonapophyses.

The

gona- pophyses are present only in the subfamily Staphylininae excepting the Xantholinini. In the other species studied thelateralplates (mor- phologically the bases of thesegmental appendages) are present,gen- erally large,and frequentlyappear

much

likegonapophysesbutw^ith- outanysignof basalarticulation. In

some

speciesthesetwoplatesare joinedbyanarroworwidebridgeoneitherthedorsal or the ventral aspect.

The

species in whichthese lateralplates are thus unitedin- cludeGcodromicus, Pelecomalium, Tanyrhinus, Lathrhnaciim,Steniis, Gastrolohium, Hesperohiwm, Lathrotropis, Stiliciis, Trachysectus, Hypocyptus, Tachyporus (fig. 28

D),

and Bolitohius.

The

species examinedin whichthesesclerites arenot united include Trigonurus, Phlococharis, Blcdius, Oxytelns,Metoponcus,Xantholinus,Xenodusa, Lorinota, Alcochara, and

Baryodma. The

greatest

amount

of union

was

found in Bolitohius inwhich the long sclerite

formed

is obvi- ouslydorsal.

On

^{the other}handin Tachyporustheunion is said

by Muir

(1920)tobeventral,andthe present observationsconfirm this.

A

very

much more

remarkablemodificationthananyotherisfound in the eighth and ninth segments of Habrocerus (fig. 28 E).

The

spiraclesof the eighthsegmentare themost important landmarks and are situated on the dorsal aspect (sp.8). According to the inter- pretation of

Muir

_(1920), which differs

somewhat from

that of

Weber

(1911)^:

....the eighth segment is highly modified and consists of four pieces.

A

large pair of pleural plates,on whichthe eighthspiraclesaresituated,embrace thelateral area, and fromtheapexof each a^{large,spine-like}stylearises;the dorsal aspect consists of a very short tergite, and the sternite consists of a largeplate more heavily chitinized roundtheedges Thelateral portion of the eighthtergite articulateswith the lateral edgesof the sterniteandalso articulates ina depressionatthebaseofthepleural plates. ...Theninth seg- mentis highly modifiedand shaped likeanoat. The distalandvisibleportion consistsofa pairofpointedandslightlycurvedlobes connected inaV-shaped pieceon thedorsal aspect; the basal and internalportions consist ofa mem-