SCANNING ELECTRON MICROSCOPIC STUDY OF THE MALE GENITALIA OF THE NORTH AMERICAN ALDERFLY GENUS SIALIS (MEGALOPTERA: SIALIDAE)

7 Pages·1991·3.5 MB·English

by  Michael F Whiting

GreatBasinNaturalist51(4), 1991,pp.404-410
SCANNINGELECTRON MICROSCOPICSTUDYOFTHE MALE GENITALIA
OETHE NORTHAMERICANALDERFLYGENUS SIALIS
(MEGALOPTERA: SIALIDAE)
MichaelF.Whiting'
—
Abstract. Scanningelectron micrographs arepresentedfor 14 species ofthe NorthAmerican alderfly Sialis:
americana,arvalis,californica.contigua,cormtta,hamata,iolajoppa,mohri,nevadensis,occidens,rotunda,vagans,
andvelata.Malegenitaliccharactersaredescribedforuseinspeciesidentification.
Keywords: Sialis,Sialidae.Megaloptera.Neuroptera,SEM.alderjlies.
There are currently 24 biological species a light microscope to evaluate genitalicchar-
of Sialis recognized from North America acters among many individuals from the 14
(Ross 1937, Townsend 1939, Flint 1964, different species. From each species a male
Whiting 1991). Ross (1937) was the first to specimen was specially dissected for SEM
illustrate and compare the genitalic charac- study. Collectiondataforthespecimensused
ters among many species ofalderflies. While in this studyare asfollows: americana (Ram-
bothCanterbury(1978)andEvans(1971)have bur):Wisconsin, GrantCo., WyalusingState
concentrated studies on the larvae ofNorth Park, 26 June 1957, A. L. Thorne; arvalis
AmericanSialis, sincetheworkofRoss(1937) Ross: California, SantaClaraCo., SanJose,
noseriousstudyhascomparedthemalegeni- AlumRockPark, 19April1987, N. D. Penny;
talia among all the North American species. californica Banks: California, Napa Co.,
A clear understanding ofgenitalic characters Napa, 2 May 1948, H. P. Chandler; contigua
is essential for proper species identification; Flint: Virginia, Smyth Co., North Fork of
consequently, there is a critical need to re- HolstonRiver, Route42, nearjunctionRoute
examine male genitalia within the genus 633, 5 May 1981, B. C. Kondratieff; cornuta
Sialis. Ross: Canada, Alberta, Konanaskis beaver
Duringastudyofthephylogeneticrelation- ponds near Lusk Creek, 6 May 1969, T. G.
ships among the North American species of Leischner;hamataRoss: Utah, WasatchCo.,
Sialis, Iusedelectron microscopytoevaluate Bryants Fork Creek near Strawberry Reser-
minutegenitaliccharacterswithgreaterclar- voir, 6June 1988, M. F. Whiting; iola Ross:
ity. The purpose ofthis paper is to present Virginia, Montgomery Co., Isaac Walton
ttihoenseloefctthreonspmeicciersoggrraopuhpssaanndd tbhreiedfidaegsncorsitpi-c PRoasrsk:PNoenwd,Ha1m1psMhaiyre,197C7o,osS.Co.M,uEdhries;Rjiovpepr,a
genitalic characters for 14 species of Sialis. Hwy. 16, Pinkham Notch, 7June 1980, Bau-
Because the micrographs better illustrate mann & Earnshaw; mohri Ross: Minnesota,
manyofthestructuresusedbyRoss(1937)in St. Louis Co., Lake Jeanette, 22 June 1964,
hiskeytotheNorthAmericanspeciesofSialis H. B. Mills; nevadensis Davis: California,
andalsoshowmanynewandimportantchar- El Dorado Co., Blodgett Forest, 31 May
acters, thispapershouldbeusefulforspecies 1969, D. Levin; occidens Ross: California,
identification. MariposaCo., MiamiRangerStation, 23May
MethodsandMaterials c1;9o4n2.,KSl.amHa.thBenCeod.i,ctW;oorodtuRnidvaerBaSnpkrsi:ngO,re1-2
Over 4000 specimens of North American June 1964, J. Schuh; vagans Ross: Virginia,
adultSialisweredissectedandexaminedwith BrunswickCo., GreefCreek, U.S. 58bridge,
MonteL.BeanLifeScienceMuseum,Brighai
)nM-llI'niversity.Ithaca,NewYork14853-0999.
404
1991 MalkGknitamaofNoHTiiAmericanSiaijs 405
25April 1982, B. C. Koiulratictl"; vclata Koss: species gronj)) or attached to a membranous
Minnesota, Louis (>(>., Eaglencst Lak(\ 1 wall. Becausetheshapeofthegenital plateis
June 1959, W. \. Balcluff. higliK speciesspecific, itisthemostdiagnos-
For specimens preserxed on pins, the last ticcharacterfordeterminingspeciesidentity.
foursegmentsof tlieabdomenwereremoved However, becauseitisalsothesmallestgeni-
and placed in a warm solution of 10% KOII talic structure and is usually concealed be-
(potassiumhydroxide)for20minutesuntilthe neath the terminal and lateral plates, it is
abdominalcuticlewas softenedand thegeni- often the most difficult structure to observe.
talia became clearK' visible. Specimens pre- The terminal plate is a single plate on the
ser\ed in alcohol did not recjuire treatment caudal end ofthe abdomen circling the bor-
with the KOH solution. The abdomens were dersoftheanus(Fig. la).Thedorsalmarginof
placed in an ultrasonic cleaning unit for 15 thisplateisreducedwhiletheventralmargin
secondstodislodgeanyforeign materialfrom isoftencleft, bilobed, ormodifiedintosingle
theirsurfaces. Theywerethenremovedfrom or double arms. Every species and species
the cleaning unit and further dissected as group of Sialis has a unique combination of
needed to expose the genitalia. The abdo- modifications of these genitalic structures,
mens were serially dehydrated in a series making species identification rather simple
of ethanol concentrations (70%, 80%, 90%, andstraightfoi-ward.
100%for15minuteseach)andthenplacedin
asolutionofacetoneovercalciumsulfatecrys- CalifornicaGroup
tals (2 hours). They were next critical-point-
dried, mountedonaluminumstubs,andgold- The Californica species group consists of
plated in a Polaron DC sputter coater in three eastern species {driesbachi Flint, iola
preparationforSEM examinationat10kv. Ross, andjoppa Ross)andsixwesternspecies
(arvalis Ross, hilohata Whiting, californica
GenitalicStructures Banks, coniuta Ross, hamata Ross, and occi-
dens Ross). This group is characterized by a
SEManalysisillustrateswithgreaterclarity conspicuous bulbous evagination on tergum
the genitalic structures useful for species 9, reduced sternum 9, andagreatlyreduced
identification within the Sialis. Ross (1937) genitalplateclothedsparsel—ywithsetae.
usedpurelydescriptivenamesforSialis geni- Sialis californica Banks. From a lateral
talia. Since adefinite homology for the geni- aspect (Fig. 6), the genital plate is saddle-
talia of aldei-flies with those ofother insect shaped and lobed behind the point ofbasal
groups has notyetbeen proposed, and since attachment. The size ofthis lobe appears to
all other species descriptions of Sialis have varyindifferentpopulations,withatendency
relied upon these same names (Townsend tograduallydecreaseas thedistributions be-
1939, Flint 1964, Whiting 1991), forthe sake comemorenorthern. Fromthedorsalaspect,
ofconsistency this paper will use Ross's de- the arms ofthe genital plate are contiguous
scriptivenames. mesallv and moderatelv covered with setae
The malegenitaliaoiSialisconsistofthree (Fig. 8J. —
majorparts: thelateral, genital, andterminal SialisoccidensRoss. Thebasalportionof
plates. The lateral plates are a pair ofovoid thegenitalplateprojectsabovetheapexofthe
plates just posterior to sternum 9 (Fig. Ic). terminalplate (Fig. 1). Thegenitalplatesare
These plates are contiguous mesally in most superficiallyshapedlike S. californicaexcept
species and covered with dense setae. In thatthebasalportionsareflangedlateradand
some species these plates are modified into devoid ofany setae (Fig. 2) and the genital
large arms bearingcoarse setae (Fig. 9). The plateisnotlobedbehindthepointofarticula-
genitalplateisasinglesclerotizedplatefound tionwiththebasalmem—brane.
posteriorto the lateral plates and anterior to SialisJianiataRoss. Theventralmarginof
theterminalplates(Fig. lb). Inmanyspecies theterminalplatebearsadark, elongatescle-
this plate is divided into two major arms rotization that projects from the base ofthe
that vary in size and length among species. terminalplateandhingesbasallytothegeni-
Basally, thegenitalplateiseitherfusedtothe tal plate (Fig. 5). The length ofthis neck is
basal portion ofthe terminal plate (Infumata reducedinnorthernpopulations. Thegenital
406 GreatBasinNaturalist [Volume51
r*3
m
^« ML^
Figs. 1-8. MalegenitaliaofStatespp.: 1, occidensRoss, a. terminalplate, b. genitalplate, c. lateralplate, d.
sternum9(ventral);2,occidensRoss,genitalplate(ventral);3,coniutaRoss,genitalplate(ventral);4,arvidisRoss,
genitalplate(ventral);5and7,haiiuitaRoss,genitalplate(anterolateralandNcntral);6and8,c(difonuc(iBanks,genital
plate(lateralandventral).
1991] MaleGenitaliaokNokiiiAmekicanSiai.is 407
plateislohed\eiitrallyandapicalK'recuiAed, covered with dense setae on the dorsal mar-
giving a distinct barl)cd-lu)()k appearance. gins(Fig. 9). —
That the caudal aspect ofthe genital plate in Sialis nevadensis Davis. This species bears
S. hatnata (Fig. 7) is identical in shape with averylarge, subrectangvdargenitalplatethat
the dorsal aspect of" the genital plate in is slightly convex. The genital plate bears a
S. cahfornica(Fig. 8)suggeststhatthese may smallpairofshorthngerlikeprojectionsonits
hesisterspecies. — uppersurface(Fig. 13). Beneatheachfingeris
Sialis conuita Ross. The terminal plate a membranous region which appears white
has the apical margins cleft, and each cleft underlightmicroscopy.
dliobveergies lparteordaullcyed(Figi.nt3o).sTwhoellegennitbaullbpslattehaits larSgiealainsdvsaugbarnesctRaonsgsi.d—arTfhreomgaenliattaelralplaastpeecits
bhstrironSaiagiagdelhditas,ntodasrttvcohaocelkniyvsaepaxirRcomaasslnsd.(mF—amirgeTg.siha3nel)s.lygoefbneitathraesltapelpraamtiiernaoilfs (t1F2h)ia.gt.Tbwe11co).osmmEea.slxlt,srtuprdooeindgnltymeedbsuafillnlbgyoeurisssaaarpeiscipanlrglolyedu(Faciregmd.
plateandisattachedventrally toaclear, sac- ontheapicalportionoft—hisbulb.
like membrane. The genital plate is strongly Sialiscontigua Flint. Basally, the genital
flangedbasallyandisapicallyproducedintoa plateissimilarinsizeandshapetoS. vagans.
pair of short fingers (Fig. 4). The terminal However,themedianarmisnarrowerandthe
plate bears a pair oflarge lobes apically (not apicalfingersarelongeranddivergelaterally
vbirsoSiiabadlleibsiunjtFoipsglp.iag4h)t.Rloyssc.on—stTrhicetegdenointatlhepllaatteerails TfofrhotemhettehUremcimlneoadsleilapyllaaptpoepirinsetsUos-fesdah.tatpaecdhmweintth(tFhieg.ar14m)s.
margins. Apically, the genital plate is pro-
duced into a pair ofshort fingers (Fig. 15). InfumataGroup
Lateral to the genital plate and posterior to
the terminal plates are apairofclear, mem- The Infumata species group comprises
branousextrusions—. eightspecies: concava Banks, hasta Ross, in-
Sialisiola Ross. Thegenitalplateiselon- fumata Newman, itasca Ross, mohri Ross,
gate, rectangular, andapicallyproduced into nina Townsend, spangleri Flint, and velata
apairofshortfingers. Theterminalplatehas Ross. All ofthese speciesare eastern ormid-
theapexnarrowandtaperingtoabluntpoint westernexceptvelata,whichoccursthrough-
(notvisibleinFig. 16). out North America. This group is character-
izedbyashield-shapedgenitalplatebearinga
AequalisGroup longpairofwhiplikearms.Thegenitalplateis
completely fused to the basal portion ofthe
TheAequalisgroupconsistsoftwowestern terminal plate and is devoid of setae. The
species(nevadensisDavisandrotundaBanks) lateralplatesareelongate, sternum9is mod-
and three eastern species {aequalis Banks, erately large, and tergum 9 lacks a bulbous
contigiia Flint, and vagans Ross). This group evagination. —
is characterized by a large, relatively unspe- Sialis velata Ross. The genital arms are
cialized genital plate devoid of setae and a longandcurve90degreesbeforeattachingto
large, flaplike sternum 9. Tergum 9 rarely the genital plate. These arms fuse together
bearsabulbousevagina—tion. beforereachingthegenitalplate(Fig. 17)and
Sialis rotunda Ross. The genital plate is bearamedianlobethatisnearlyone-halfthe
subdivided into two concave halves that length of the arms. The terminal plate,
serve as receptacles for the apical portion quadrateand slightlycleft, is basallyfusedto
ofthelateralplates(Fig. 9). Twostockygeni- thegenitalplate. —
tal hooks arise from the median evaginated Sialis mohri Ross. The genital arms are
ridge on the genital plate. These hooks longbut stockier than S. velata. The median
runparallelandaremoderatelyrecurvedven- lobe ofthe genital arms is absent (Fig. 18).
trad(Fig. 10). The terminalplate is quadrate Theterminalplatebearsapairoflong,heavily
and only slightly cleft (Fig. 9). The lateral sclerotized arms that converge medially (not
plates are produced into apairofbluntarms visibleinFig. 18).
408 GreatBasinNaturalist [Volume51
BanFkigss,.g9e-n1i4t.alpMlaaltee(gveennittraalli)a;o1i1Siaalnids1s2p,p.v:a9g,arnostRuonsdsa,Bgaennki.tsa,llpalteartael,(lgaetneirtaalla,nadndvetnetrramli)n;al13p,lanteevsac(vleensh1D);a\1i0s,,rogetnuintdaal
plate(lateraloblique);14,contiguaFlint,genitalplate(ventral).
AmericanaGroup run nearly parallel but diverge slightly
laterally. The genital plate and arms do not
The Americana species group consists of
twoeasternspecies: amchcana(Rambur)and bearsetae.
glabella Ross. This group is distinguishedby
thelarge, unspecializedgenitalplate, moder- Discussion
arltaeecdlkyscolslaeortrgaaeet,isotanenordfnutsmhtee9r,bnoaudmnyd.9tThhleaecukgnseincaijtubaelu,lpbllioaguthset ofTfhieeldhiagvhaielrambalegnimfaikceatiSoEnMandagvraelautaebrledetpotohl
evaSgiianliastioanm.ericana Rambur.—The genital froerlaitnivoenssthiigpastiwnigtheivnoltuhteioSnkialrlys.aSndEMtaxaonanloymsiics
plate is triangularand mesallybears apairol ofNorthAmericanSiallshasrevealedthatthe
long, broad arms (Figs. 19, 20). These arms genitalstructuresareclearK diagnosticforall
1991] MaleGknitaliaokNohthAmericanSialis 409
Figs. 15-20. MalegenitaliaofSialisspp.:15,joppaRoss,genitalplate(ventral);16,tolaRoss,upperhalfofgenital
plate (ventral); 17, velata Ross, genital and terminal plate (lateral oblique); 18, mohri Ross (lateral); 19 and 20,
arnericana(Rambur)genitalplate(ventralanddorsal).
14 species studied and that these structures microscopyhaverevealedthattherearechar-
arethekeytounderstanchngevolutionaryre- acteristicsbettersuitedforspeciesidentifica-
lationshipswithintheSialidae. tion thanthoseusedinthekeyofRoss. Some
All species identifications ofadult Sialidae ofthesecharactersareillustratedandoutlined
in North America have relied upon the key above.Therefore, useofthesemicrographsin
publishedbyRoss(1937). Afterworkingwith conjunction with Ross's key will aid in more
this key for several years, I have found that accurateidentificationofSialisspecies.
some couplets are ambiguous because they
rely on characters that are either obscure or Acknowledgments
artificial. Compounding this problem are
sketchy drawings that only partially reflect 1 thank Wilford M. Hess, James V. Allen,
the actual structure. SEM analysis and light and Connie Swenson ofthe Electron Optics
410 GreatBasinNaturalist [Volume51
Laboratory at Brigham Young University for P^LINT,O S 1964. Newspeciesandnewstaterecordsof
theirhelpwithtechnicalandcriticalaspectsof Sialis(Neuroptera:Sialidae).EntomologicalNews
RsciacnhnairndgWe.leBcatruomnanmincraonsdcoSptye.phIenalLs.o Wthoaondk Ross.H7I..5H;N9e-a11r93c3.t7i.cStaluddeirefslioefstohfetNheeargcetnicusaqSuiaatliisci(nMseecgtas.-
forreviewingearlydraftsofthismanuscript. loptera: Sialidae). BulletinoftheIllinoisNatural
HistorySurvey21;57-78.
Townsend.L. H 1939. AnewspeciesoiSialis (Mega-
LiteratureCited loptera: Sialidae)from Kentucky. Proceedingsof
theEntomologicalSocietvofWashington41:224-
Canterbury. L. E. 1978. Studies on the genus Sialis 226.
(Sialidae:Megaloptera)ineasternNorthAmerica. Whiting. M F 1991. A new species ofSialis (Mega-
Unpubhshed thesis. University of Louisville, loptera:Sialidae)fromsouthernCalifornia. Great
Louisville,Kentucky.93pp. BasinNaturalist51;411-413.
Evans, E. D. 197L A study ofthe Megalopteraofthe
PacificcoastalregionoftheUnitedStates.Unpub-
lisheddissertation,OregonStateUniversity,Cor- Received14Juhj1990
vallis.210pp. Accepted1August1991