Table Of Content©EntomologicaFennica.31May2011
Description of the first larval instar of Broscus crassimargo
Wollaston, 1865 (Carabidae: Broscini) and notes about the
presence of the species in the mesovoid shallow substratum
of La Gomera (Canary Islands, Spain)
JoséD.Gilgado,HeribertoLópez,PedroOromí&VicenteM.Ortuño
Gilgado,J.D.,López,H.,Oromí,P.&Ortuño,V.M.2011:Descriptionofthe
firstlarvalinstarofBroscuscrassimargoWollaston,1865(Carabidae:Broscini)
andnotesaboutthepresenceofthespeciesinthemesovoidshallowsubstratum
ofLaGomera(CanaryIslands,Spain).—Entomol.Fennica22:45–55.
ThefirstlarvalinstarofthegroundbeetleBroscuscrassimargoWollaston,1865
endemictoLaGomera(CanaryIslands,Spain)isdescribed.Thisisthefirstcom-
prehensivestudyoftheprimarychaetotaxyofthethreetagmataevercarriedout
inlarvaeofBroscini,beingalsoaccompaniedbyadetailediconography.Theim-
plicationsoftheresultsofthischaetotaxyanalysisarediscussedinrelationtothe
possibleoriginofBrosciniwithinCarabidae.Commentsontheecologicaldeter-
minants for its remarkable presence in the mesovoid shallow substratum are
given,analysingthedifferencesbetweenLaGomeraandotherCanaryislands
wheresamplingsinthesamesubterraneanhabitathavebeencarriedout.
J. D. Gilgado (corresponding author) & V. M. Ortuño, Departamento de
ZoologíayAntropologíaFísica,FacultaddeBiología,UniversidaddeAlcalá,E-
28871 Alcalá de Henares, Madrid, Spain; E-mail: josedomingo.gilgado
@uah.es&[email protected]
H.López,DepartamentodeBiologíaAnimal,UniversidaddeLaLaguna,38206
LaLaguna,Tenerife,CanaryIslands,SpainandIslandEcologyandEvolution
Research Group (IPNA-CSIC), 38206 La Laguna, Tenerife, Canary Islands,
Spain;E-mail:[email protected]
P.Oromí,DepartamentodeBiologíaAnimal,UniversidaddeLaLaguna,38206
LaLaguna,Tenerife,CanaryIslands,Spain;E-mail:[email protected]
Received30June2010,accepted29October2010
1.Introduction accordingtosomeotherauthors(Bousquet2003)
or even to the family Broscidae (sensu Jeannel
The classification of the genus Broscus Panzer, 1941). Ball (1956) recognized three subtribes
1813 and related genera has been controversial within Broscini: Broscina, Barypina and
fordecades.Thisgroupofgroundbeetlesisoften Creobiina, sections that were previously pro-
given the status oftribe Broscini (Britton 1949, posed by Jeannel (1941) with the status of
1964, 1970, Ball 1960, Darlington 1965, Roig- subfamilies. Recently, Roig-Juñent (2000) pro-
Juñent2000,Pawsonetal.2003,amongothers) posedtwosubtribesmore:AxonyinaandNotho-
which is equivalent to the subfamily Broscinae broscina.Theincreasinglyrigorousstudieshave
46 Gilgadoetal. • ENTOMOL.FENNICAVol.22
broughtanewperspectiveofdiagnosticcharac- ginperfectlyreachingthebasalanglesofthepro-
ters for these subtribes, and in the last analyses notum (Wollaston 1865, Machado 1992). It is
some genera have been relocated again (Roig- easily foundpractically inthewholeareaoccu-
Juñent2000).Mostofthetaxaareuniquetothe piedbythe“monteverde”forest(theproperlaurel
SouthernHemisphereandasmallpartispresent forestplusthesocalledfayal-brezal)ofthecen-
intheNorthernHemisphere,especiallyinthePa- tralmountainsofLaGomera,onlyavoidingthe
laearcticregion.Thisdistribution,andacladistic drier wooded zones facing southwards. Wol-
analysis based on 73 morphological characters laston (1865) did not mention this detail, but it
led Roig-Juñent (2000) to propose the origin of mustbeconsideredthatLaGomerawastheonly
Broscini on the Pacific coast of Pangaea, in the islandhenevervisited,havingdescribedthisand
early Jurassic. Although different origins have manyotherGomeranbeetlespeciesaccordingto
beensupposed(Jeannel1942,Britton1949,Ball the material provided by Crotch. Both Broscus
1956,Darlington1965,Erwin1985),thisseems andCarabusLinnaeus,1758aregenerawithfew
tobethemostparsimonious.Furthermore,amo- speciesontheCanaries,andintheislandswhere
lecularanalysis(Maddisonetal.1999)hasalso they occur together they usually share habitat,
suggestedaratherearlydivergence. probably competing for similar food resources
Inlightofthecurrentknowledge,contraryto giventheircomparablesizeandhabits.Themark-
Bousquet(2003)andinaccordancewiththecrite- edly higher abundance of B. crassimargo in re-
rion of Roig-Juñent (2000), the Broscini of the specttotheothertwospeciesofBroscuscouldbe
Palaearctic region are assignable to two sub- duetotheabsenceofCarabusinLaGomera,a
tribes: Broscina and Axonyina, the latter being genus present in Tenerife (Carabus abbreviatus
themostdiverseanddisparate.WithinBroscina Brullé,1835andCarabusfaustusBrullé,1839)
thegenusBroscusisthemostrepresentative(25 andinGranCanaria(CarabuscoarctatusBrullé,
species)andwidelydistributed,beingpresentin 1839).BroscusrutilansfromTenerifeisfoundin
Asia, Europe, North Africa, the Canary Islands themarginalzonesabovethelaurelforest(fayal-
and introduced in North America (Bousquet brezal),inthehumidpineforestontheNorthof
2003). theisland, andsometimesinthetransitionzone
ThegenusBroscusisrepresentedintheCana- between the pine forest and the high mountain
rianarchipelagobythreecloselyrelatedspecies, scrub(Machado1992,owndata).Carabusabb-
eachoneendemictoasingleisland:Broscusgla- reviatusisalsofoundinpracticallyalllocations
ber(Brullé,1836)fromGranCanaria,B.rutilans whereB.rutilansoccurs,andusuallymoreabun-
Wollaston, 1862 from Tenerife and B. crassi- dantlythanthelatter.InGranCanaria,B.glaber
margo Wollaston, 1865 from La Gomera. Ac- is typically occurring in the mountain forest ar-
cordingtoAntoine(1955)andMachado(1992) eas, mainly in more or less humid pine woods,
they are probably related to B. politus (Dejean, thoughactuallyitisalsofoundinopendeforested
1828) from North Africa and Sicily, for having areas.AtthetimeofWollaston(1864)itwasalso
theejaculatoryducthighlysclerotized,acharac- collectedinformerwoodlandsitesatloweralti-
terabsentintheremainingspeciesofthegenus. tudelikeElMonte,whereitdoesnotliveatpres-
However,theshapeoftheCanarianspeciesdiffer ent.ItusuallycoexistedwithCarabuscoarctatus,
bytheirelytrabeinglessconvexandwithmore butbothspecieshavebecomeparticularlyscarce
ovateoutline(subparallelinB.politus)seenfrom nowadays. In any case, B. crassimargo in La
above, and they are micropterous contrarily to Gomeralaurelforesthaspopulationdensitiesal-
B.politus,probablyduetotheiradaptationtoin- ways higher than the combined individuals of
sularenvironments. CarabusandBroscusperareainanybiotopeof
Broscus crassimargo is the largest (20–24 TenerifeorGranCanaria(ownobservations).
mm),themoststrictlyforest-dwellingandbyfar Broscuscrassimargoisaspeciesusuallyoc-
themostabundantofthethreeCanarianspecies, curringunderstonesandfallentrunks,andithad
beingalsodifferentbyitsblackishfirstantenno- alsobeenrecordedbyMedina&Oromí(1990)in
mere(darkredintheothertwospecies)andbyits the mesovoid shallow substratum (henceforth
duller,moreflattenedelytrawiththelateralmar- MSS;seeJuberthie1983andCulver2001).Me-
ENTOMOL.FENNICAVol.22 • FirstinstarlarvaofBroscuscrassimargo 47
dina(1991) considered that B. crassimargohad ofthemwereplacedfivemetersapart,separated
beencollectedinthisparticularsubterraneanhab- two hundred meters from the other two in the
itatjustoccasionally.However,ithasbeencap- same conditions. The traps were working from
tured repeatedly along a recent study on the ar- January2008toJune2010,theircontentsbeing
thropodfaunaintheMSSofLaGomeralaurelfo- revisedtwiceayear(January/FebruaryandJune/
rest(unpublishedowndata).Mostoftheindivid- July).Thesamplesofeachtrapwerefilteredon
ualscollectedinthetrapsareadults,butalsoone place and kept in separate vials with propylene
larvaofthisspecieshasbeenobtained.Thelarva glycol,veryappropriatetopreservetheDNAof
ofB.crassimargo(aswellasthoseofanyCana- thecapturedindividualsforgeneticstudies(Ru-
rianBroscus)waspreviouslyunknown.Accord- binketal.2003).
ingly,larvaldescriptionanditscomparisonwith
thearchetypicalmodelproposedbyBousquet&
Goulet(1984)isthemainsubjectofthepresent 2.2.FirstinstarlarvaofBroscuscrassimargo
article.Thismeansthat,afterthedescriptionofB.
cephalotes(seeLuff1978,Sharova&Makarov Afirstinstarlarvawasobtainedon04/01/2010.
1984)andB.punctatus(seeSharova&Makarov This larva was dissected, extracting the labium,
1984),thisisthethirdBroscusspeciesonwhich mandibles, maxillae, antennae, cephaliccapsule
datarelatedtothelarvaearegiven. sclerites,legs,andtergalandsternalscleritesby
using dissection tweezers. These pieces were
soakedinthewater-solubleresinDimethylHy-
2.Materialsandmethods dantoin Formaldehyde (DMHF) (Steedman
1958)andplacedonacetatesheetsforuseasmi-
2.1.Studyareaandsamplingmethod croscope slides, which measured 1.5 × 0.5 cm.
Anothersmallacetatesheetwasplacedoneach
ThesamplingwascarriedoutatReventónOscuro slideasacoverslipforobservationunderthemi-
(UTM28R282330/3113130), alocationwithin croscope.Themicroscopeslideswiththelarvae
GarajonayNationalPark(LaGomera,CanaryIs- dissected are deposited at Vicente M. Ortuño’s
lands)whichincludesoneofthebestrepresenta- (VMO/AU) collection at the Department Zool-
tionsofhumidlaurelforestinthearchipelago.A ogyandPhysicalAnthropologyoftheUniversity
debrismesovoidshallowsubstratum(MSS)(see ofAlcalá.
Juberthie 1983) on a steep slope was selected, ThehabituswasdrawnusingaNIKONSMZ-
originated by colluviation at the base of rocky 1000 stereoscopic binocular microscope. Each
cliffs,butprobablyalsoincreasedbystonydebris preparationwasobservedandmeasuredwithan
slippingdownslopeduringtheconstructionofan optical microscope ZEISS 474620-9900, with
old forest road. These colluvia are formed by cameralucidaandacalibratedocularmicrometer.
mid-tosmallsizestonescoveredbyathinlayer Thehabitusandpreparationsweredrawninink.
ofsoil,constitutingasubterraneanhabitatwitha The drawings were scanned and labelled using
network of abundant interstices suitable for an theapplicationAdobePhotoshopCs8.0.
abundantfauna.Thethicknessofthesecolluviais The adopted nomenclature for the setae and
unknown, but according to our prospections pores is that proposed by Bousquet & Goulet
whensettingthetrapstheymustreachatleast1m (1984). According to this criterion, setae are
deep. The canopy cover of the area is close to namedwithnumbers,andporeswithletters.The
100%, evergreen trees Laurus azorica (Seub.) supernumerary setae are named with Roman
Franco, Ilex canariensis Poir., Picconia excelsa numbers, and supernumerary pores with Greek
(Aiton) DC. and Myrica faya Aiton being the letters,whentheyarepresent.
dominantspecies,providingapermanentpenum- In some parts of the anatomy of the larva it
bra to the surface and humidity to the under- wasimpossibletoidentifysomeparticularpores,
groundlayer. since more than one of those were found in the
Four collecting traps were set following the sameareawheretheyshouldbelocated,accord-
modeldescribedbyLópez&Oromí(2010).Two ing to the archetype proposed by Bousquet &
48 Gilgadoetal. • ENTOMOL.FENNICAVol.22
Table1.No.ofBroscuscrassimargoadultsandone
larvacollectedinthetraps.
Samplingperiod No.
04/01/2008–01/07/2008 1
01/07/2008–01/02/2009 15
01/02/2009–30/06/2009 4
30/06/2009–04/01/2010 18+1larva
04/01/2010–08/06/2010 1
Goulet (1984). In such cases, the application of
theterminologyforgroupsofstructureswascho-
sen,asithadbeenoccasionallydonewithsome
setae. Examples are the groups of pores gPRi,
gPRj,gMEe,amongothers.
3.Results
3.1.CollectedBroscuscrassimargo
andotherinvertebrates
Inthisstudy39adultsandonelarvaofB.crassi-
margowerecapturedintheMSStraps,butindif-
ferentnumbersdependingonthesamplingperi-
od,sothatthetotalspecimens(Table1)collected
ineachperiodishigherinthesecondhalfofeach
year. Besides B. crassimargo, we collected in
thesetrapsawiderangeofinvertebratesthatoc- Fig.1.HabitusofthefirstinstarlarvaofB.crassi-
margo.Scalebar2mm.
cupytheundergroundhabitatofthisarea,varying
from species with marked subterranean adapta-
tionstonon-adaptedspeciesthatventureunder- and Aptilotus sp. (Diptera). Other epiedaphic
groundoccasionallyoraccidentally.Thebeetles carabids like Calathus laureticola Wollaston,
Pseudoplatyderus amblyops Bolívar, 1940, Do- 1865, Trechus flavocinctus gomerae Jeannel,
mene jonayi Hernández & Medina, 1990 and 1936, Paraeutrichopus harpaloides (Wollaston,
EuconnusspecususVit,2004,andthemillipede 1864) and Dicrodontus aptinoides (Wollaston,
GlomeriscanariensisGolovatch,1987standout 1865) were collected occasionally. However,
in the first group. Several edaphobionts with a epigean species of Calathus Bonelli, 1810 and
lower degree of subterranean adaptation were CymindisLatreille,1806frequentlyfoundonthe
also collected, particularly the beetle Aeletes surface around the traps were never caught in
gemmula (Wollaston, 1865) and the millipede theseMSSsamples.
Blaniulussp.besidesabundantoribatidmites.Fi-
nally, the humicolous and epiedaphic species
3.2.Descriptionofthefirstinstarlarva
weretherichestandmostdiversegroupcollected
ofBroscuscrassimargo
inthesetraps,withanotableabundanceofPlut-
onia oromii (Ibáñez & Alonso, 1988) (Pulmo- Habitus (Fig. 1). Dark brown to reddish larva,
nata), Brachydesmus sp. (Polydesmida), Eluma 18.7 mm long from the nasale to the apex of
caelata (Miers, 1877) (Isopoda), Gomerina pygidium. Massive head (almost as wide as the
calathiformis (Wollaston, 1865) (Coleoptera) pronotum), body gradually tapering backwards,
ENTOMOL.FENNICAVol.22 • FirstinstarlarvaofBroscuscrassimargo 49
Fig.2.Firstinstarlarva
ofB.crassimargo.Ce-
phalicpieces.–a.
Frontale.–b.Parietalin
dorsalview.–c.Pari-
etalinventralview.
–d.Labiumindorsal
view.–e.Rightmaxilla
indorsalview.–f.Right
maxillainventralview.
–g.Rightmandiblein
dorsalview.–h.Right
antennaindorsalview.
–i.Rightantennain
ventralview.Scale
bars,a–c:1mm;d–f:
0.5mm;g:1mm;h–i:
0.5mm.
as in the third instar of Broscus cephalotes ac- (PA1–PA19),lackingsetaPR8,butwithonesu-
cording to the description by Luff (1993); rela- pernumerary PRI. There are only eight distin-
tivelyshortlegs. guishablepores(PAa-PRd,PRk,PRm-PRo).La-
Cephaliccapsule.Epicranialsuturelessthana bium(Fig.2d)withthreepores(LAa–LAc)and
thirdofthefrontalelength.Frontalealmosttrian- only four distinguishable setae (LA2–LA3,
gular,1.61mmlongand1.98mmwide(Fig.2a). LA5–LA6); it is so pubescent dorsally that the
It bears ten setae (FR1–FR10) and five distin- setaeLA1andLA4areindistinguishable.There
guishable pores (FRa–FRd) at each side of the isaveryshortprotuberance,correspondingtothe
sagittalplane,oneofthemsupernumerary(FR(cid:1)), ligula,withtwosetae(LA6)almostaslongasthe
andlackingFRc.Therearetwoeggbursters.The last labial palpomere. Maxillae (Figs. 2e,f) ap-
nasale is almost flat, but slightly curved and proximately1.86mminlength,pubescentinthe
slightly acuminate at the extremes. Parietale inner dorsal face. Palp cylindrical, with four
(Figs.2b,c)withsixstemmataaroundtheocular palpomeres.Galeawithtwogaleomeres,approx-
protuberance. The parietale has a conspicuous imately as long as the two first palpomeres.
lateral constriction, and bears eighteen setae Lacinia absent. The maxilla bears ten setae
50 Gilgadoetal. • ENTOMOL.FENNICAVol.22
Fig.3.Firstinstarlarva
ofB.crassimargo.–a.
Pronotum.–b.Pro-
thoraxandmesothorax
inventralview.–c.Me-
sonotum.–d.Protho-
racicrightleg.–e.Pro-
thoracicrightleg.–f.
Abdominaltergite-I.
–g.Sterniteand
pleuritesextendedof
abdominalsegment-I.
Scalebar:1mm.
(MX1–MX11), MX6 indistinguishable because eleven setae (PR1–PR14), PR5, PR7 and PR13
ofthepubescence,andMX12absent;andeight absent;andeighteenpores(PRa–PRg):PReand
pores (MXb–MXc, gMXe, MXf–MXg) with a PRhareabsent,butintherelativepositionofPRi,
supernumerary pore in the third palpomere PRj, PRk and PRl there are groups of pores
(MX(cid:1)),intherelativepositionofMXethereare (gPRi–gPRl)severalpores.Prosternum(Fig.3b)
threepores(gMXe)andtheporeMXaisabsent. withgPS,PS1andPS2present.Episternum(ES)
Mandible sharp, long (1.69 mm in length) and andepimeron(EM)fused,withasclerotizedre-
curved(Fig.2g),withoneseta(MN1)andthree gionbetweenthem,eachonebearingagroupof
pores(MNa–MNc).Itbearsashortbutsharpened setae(gESandgEM).Mesonotum(Fig.3c)1.40
retinaculum.Antennae(Figs.2h,i)1.66mmlong, mminlengthand3.22mminwidth,bearingfour-
with four antennomeres, and a sensory append- teen setae (ME1–ME14) and thirteen pores
ageonthethirdone;itbearssevensetae(AN1– (MEa–gMEl); there are several supernumerary
AN7), with AN6 very reduced and only five pores, the ME(cid:1) and, similarly to the pronotum,
pores (ANa–ANe), since ANf and ANg are ab- groupsofpores(gMEeandgMEf)intherelative
sent. position of the pores MEe and MEf. Meso-
Thorax.Inallthoracictergitesthereisavisi- sternumbearingsixsetae(MS1–MS6),trochan-
blemedialsuture.Pronotum(Fig.3a)2.22mmin tin with a group of four setae (gTS1) and epi-
lengthand3.37mminwidth,withalateralcon- meronwithanumerousgroupofsetae(gEM1).
strictionapproximatelyinthefirstthird,bearing Pleuronwithalongseta(PL1).
ENTOMOL.FENNICAVol.22 • FirstinstarlarvaofBroscuscrassimargo 51
Fig.4.Firstinstarlarva
ofB.crassimargo.–a.
Urogomphiindorsal
view.–b.Pygidiumin
dorsalview.–c.Pygi-
diuminventralview.
Scalebar:1mm.
Legs(Figs.3d,e).Similarinsizeandchaeto- aconspicuousspiracle,whichisnotpresentinthe
taxy,withoneclaw,lesspigmentedthantergites, restofabdominalsegments.Theurogomphi(Fig.
andrelativelyshortmeasuring4.23mmapproxi- 4a) are 2.75 mm long, similar to the model of
matelyfromthebasisofthecoxatothetipofthe Bousquet & Goulet (1984), bearing nine setae
claw.Thedescriptionisbasedontheprothoracic (UR1–UR9)andsevenpores:(URa–URf),with
leg.Coxawithsixteensetae(CO1–CO17),lack- URd and URg absent, and two supernumerary
ingCO10.Threevisiblepores(COa–COc).Tro- (UR(cid:1)andUR(cid:3)).Pygidium(Figs.4b,c)1.36mm
chanter with eight setae (TR1–TR8), and seven in length and 0.53 mm in width approximately,
pores (COa–COg). Femur bearing seven setae bearing seven setae (PY1–PY7), lacking PY4
(FE1–FE7)andtwopores(FEaandFEc).Tibia andPY5,andincludingtwosupernumerary(PYI
withsevensetae(TI1–TI7)andtwopores(TIa– and PYII). There are six pores: (PYa, PYb and
TIb).Tarsuswithfivesetae(TA1–TA7),lacking PYf),threeofthemsupernumerary(PY(cid:1)–PY(cid:2)).
TA3andTA6;setaeTA4andTA5veryreduced.
Claw with two conspicuous setae (UN1 and
UN2). 4.Discussion
Abdomen.Lengthapproximately10.37mm,
measuredfromthefirstabdominalsegmenttothe 4.1.FirstinstarlarvaofBroscuscrassimargo
end of the pygidium. The abdominal tergite-I
(Fig.3f)is0.94mminlengthand2.61inwidth.It The effectiveness of larval characters to build a
bearselevensetae(TE1–TE11)andsevenclearly precisebeetlesystematicshasalreadybeendem-
distinguishable pores, (TEa–TEd) and three su- onstrated (Beutel 1993, Solodovnikov 2007).
pernumerary (TE(cid:1)–TE(cid:2)). The sternites of ab- Thisisthereasonwhereby moreandmorespe-
dominalsegment-I(Fig.3g)withfoursetae(ST1, cificstudiesonlarvalcharactershavebeenincor-
ST2,ST4andST6),andtwogroupsofsupernu- porated to the first treatises and compendia on
merarysetae(gST3andgST5)intherelativepo- Coleoptera larvae. Preimaginal characters pro-
sition of ST3 and ST5 respectively. There is a videagreatdealofanatomicalinformation,inad-
poreST(cid:1).Theepipleuritebearstwosetae(EP1 dition to those already available on the imagos.
and EP2). Hypopleurite with a well developed Clearly,thelarvaisveryrelevantforsystematics
setaHPI,andagroupofsetaegHPII.Thereisalso asitisanothergenotypicexpressionofthespe-
52 Gilgadoetal. • ENTOMOL.FENNICAVol.22
cies(Goulet1979,Luff1993)andfromtheeco- lotesisathirdinstarlarva,andthatofB.crassi-
logicalpointofview,theyoftenoccupydifferent margoafirstinstar,thedifferencesbetweenthem
niches and can exploit different food resources. couldbeduetotheirdifferentstagesofdevelop-
For this reason, the selective pressures do not mentandthereforewouldnotbeusefulforspe-
needtobethesameinlarvalandadultstages,and cific discrimination, therefore those differences
the preimaginal instars can show very different are not presented here. However, the study of
evolutionaryrhythmsthantheimagoes.Asare- chaetotaxyinthefirststageofB.cephalotesusing
sult,theycanshowalready“lost”featuresinthe thecriterionofBousquet&Goulet(1984),most
imagoes,whichcouldhelptoinferthephylogen- likelywouldrevealmoresignificantdifferences
eticrelationshipsofspecies. withrespecttoB.crassimargo.
However,thestudyofpreimaginalmorphol- ThestudyofthelarvaofB.crassimargohas
ogy posesaseriesofdifficulties(Solodovnikov revealed an extraordinary resemblance (number
2007) which are, of course, also present in the and topology of pores and sensory setae) to the
study ofthelarvaofB.crassimargo:a)thelow model of Bousquet & Goulet (1984), although
numberofspecimensincollections,b)theneedto theydidnotuseanyspeciesofBroscinithatcon-
dissect and make preparations for microscopic tributed with its characters to the archetypical
observationofsomestructures,c)theexistenceof proposal.Thisrelatestotheprimitivenessofthis
intraspecific variability in some characters such group of Carabidae. Very probably the diver-
aschaetotaxy(incaseofasinglespecimenmay genceoftheBroscinifromotherCarabidaehada
bediscerniblebyasymmetryonbothsidesofthe verybasalorigin,andsotheycouldhaveretained
sagittalplane),andd)thedifficultyofdetermin- muchoftheearlylarvalcharacters.Thisevidence
ingwhetheracharacterishomologousornotin coming from the study of larval chaetotaxy is
severaltaxa. supportedbyotherstudiesonimaginalmorphol-
Thefindingandstudyofthepresentlarvaof ogy (Roig-Juñent2000),andmolecularbiology
B. crassimargo is a return to the incipient re- (Maddisonetal.1999).
search line on the preimaginal stages of the en- It is possible that the species of this lineage
demic Canarian Carabidae (see Raynaud 1970, havemaintainedalifestyleverysimilartoprimi-
Arndt1991).AccordingtoMachado(1992),this tivespecies,notbeingnecessarytoadapttooradi-
line of research has only two earlier contribu- callytodifferentlivingconditions,thusprevent-
tions: one concerning Carabus abbreviatus ing remarkable structural changes (apomor-
(Carabinae)andtheothertoZarguscrotchianus phies).Inrelationtothis,Erwin(1985)postulates
Wollaston,1865(Licininae). thatthefirstgroundbeetleswerenaturalofhigh
Furthermore,thedescriptionofthislarvabe- humidity,orwater-relatedenvironments,assug-
comesimportantfromamethodologicalpointof gestedbyitsrelationshiptootherAdephagalike
view,sincethoughotherBroscinilarvaehaveal- Dytiscidae, and their almost anecdotal presence
ready been described (Gardner 1931, Jeannel inthemostxericareasoftheplanet.Thus,thisen-
1941,Moore1964,Andersen1968,Harris1978, vironment would have been the evolutionary
1980, Luff 1978, 1993, Townsend 1971, 1988, centre of dispersal, and therefore in the most
Sharova&Makarov1984,Arndt1991,Davidson primitivegroupstendtobeorganicallylinkedto
&Ball1998),thisisthefirstspeciesofthistribe humidenvironments(coasts,riparianandmarsh
inwhichthenomenclatorialcriterionofBousquet areas,woodedareas,etc.).
& Goulet (1984) is applied, as done by Arndt
(1991)forthedescriptionofZarguscrotchianus.
Thiswillallowamoreprecisecomparisonwith 4.2.TheoccurrenceofBroscuscrassimargo
other Carabidae larvae and also with the arche- intheMSS
typeproposedbyBousquet&Goulet(1984).
So far, the most and best studied Broscini The presence of certain epigean species in the
larvaisthatofB.cephalotes(Jeannel1941,Luff Canarian MSS is a constant feature in the few
1978, 1993, Sharova & Makarov 1984). How- studiescarriedoutsofarinthisenvironment(Me-
ever,giventhatthedescribedlarvaofB.cepha- dina1991,Medina&Oromí1990,Oromíetal.
ENTOMOL.FENNICAVol.22 • FirstinstarlarvaofBroscuscrassimargo 53
1986,owndata),includingsomemediumtolarge (winter/spring), a more humid period when po-
size beetles (Carabidae and Staphylinidae) like tential prey are abundant in epigean environ-
Broscus, Carabus, Ocypus Leach, 1819 and ments.Asimilarpatternofcaptureshasbeenob-
ProtogoeriusCoiffait,1956.Butsuchspeciesoc- servedinthepredatorybeetlesEuconnusspecu-
curparticularlyintheMSSswithmoreinterstitial susandOcypussilvaticusWollaston,1865.Prob-
profusion,usuallycoincidingwiththoseofcollu- ably the latter is more abundant in the sum-
vial origin (debris MSS). Contrarily, the MSS mer/autumn for the same reasons as B. crassi-
formed by volcanic clinker is usually more iso- margo,buttheabundanceofE.specususisprob-
lated from the surface and their interstices are ablyrelatedtoitsnaturalphenology,sinceitisa
moresealed,consequentlybeinglesspracticable troglobiont beetle which permanently occupies
forbigepigeanspeciesusuallylargerthanthose an underground layer hardly influenced by sea-
adaptedtoliveunderground. sonalchanges.
As we have observed along years of studies ItisstatedthatB.crassimargooccursrather
on this subterranean fauna (unpublished data) frequentlyintheMSSherestudied,butitisnot
BroscusandCarabushavesometendencytoen- clearwhethertheyjustoccupyshallowlayersor
ter in such colluvia. However, no Broscus have reach deeper levels of the colluvium. The trap
ever been collected in the MSS of Tenerife or modelwehaveusedworksidenticallyforarank
GranCanaria,whilethelocalspeciesofCarabus between15and80cm.Tosolvethisquestionit
were sometimes present (occasionally even wouldbenecessarytouseaselectivetrapfordif-
abundantincertaintrapsinTenerife).Thepres- ferent depths (see Schlick-Steiner & Steiner
enceofB.crassimargointheMSSofLaGomera 2000,Laškaetal.2008,inpress).
couldsuggestthat,giventheabsenceofCarabus LarvaeofCarabusorBroscushadneverbeen
inthisisland,theformerhasoccupiedanichenot capturedbeforeintheMSSoftheCanaryIslands,
availableintheothertwoislandsduetothecom- forwhichprobablytheirpresenceinthisenviron-
petition of Carabus. The absence of large sized mentcouldbeoccasional,contrarilytotheadults,
troglobiticgroundbeetlesprobably favoursthat which are relatively common as commented
BroscusandCarabusinvadetemporarilytheun- above.Accordingtotheecologicalclassification
dergroundtoexploitanemptyniche.Instead,in proposed by Sharova (2008), the larvae of
the present case study in La Gomera there is a Broscusaregeobiontsbelongingtothe“burrow-
poorrepresentationofmidtosmallsizeepigean ing forms”, and this soil burrowing lifestyle is
ground beetles with the exception of Gomerina also confirmed by the morphology of their tho-
calathiformis,aspecieswithcleartendencytoin- racicendoskeleton(Zaitsev2008),somaybeset-
vade shallow underground layers and already tingtrapsinthepropersoilaroundthesiteswhere
capturedbyMedina(1991)intheMSSofthisis- B. crassimargo has been obtained in the MSS,
land.Thisscarcitymustbeduetotheabundance could be useful to check their endogean or
ofthetroglobiticPseudoplatyderusamblyopsin hypogeanpreferences.Thelatterislessprobable
the samples, a blind 9 mm long ground beetle since debris MSS sites are not easy to find and
whichisbyfarthemostabundant(asmuchas247 probably represent a minimum part of the total
individualscollected)amonganysizecategory. distributionalareaofthespeciesinLaGomera.
Probably both Broscus and Carabus invade
theMSSfollowingpreyssuchasslugsthatneed Acknowledgements.WewanttothankVerónicaGonzález
high humidity, always present in the MSS but Araujoforrevisingthegrammarandforhersuggestions
withtheEnglish.Thisstudyhasbeenpartiallyfinancedby
onlyseasonallyonthesurface.Thiscouldexplain
theI3programof“IncentivationoftheIncorporationand
whythenumberofBroscuscollectedintheMSS
IntensificationonResearchActivityoftheMinistryofEd-
at Reventón Oscuro laurel forest was much ucationandScienceofSpain,ofwhichVicenteOrtuñois
higherinthesummer/fallthaninthemorehumid thebeneficiary,andbythe025/2007researchprojectofthe
winter.Onthecontrary,afterananalysisofsur- alsoSpanishMinistryofNatural,RuralandMarineEnvi-
ronmentcarriedoutbyP.Oromí,H.Lópezandcollabora-
facerecordsofB.crassimargointhelaurelforest
torsinGarajonayNationalPark.
of Gomera, Machado (1992) pointed out that it
was more abundant in the first half of the year
54 Gilgadoetal. • ENTOMOL.FENNICAVol.22
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