Description of the larva of Lestes virgatus (Burmeister) and comparisons with some other south African Lestidae (Zygoptera)

9 Pages·1992·1.5 MB·English

by  Samways, M J

Odonatologica21(4):505-513 December I.1992
Description of thelarva of Lestes virgatus
(Burmeister) and comparisons with some other
south African Lestidae
(Zygoptera)
M.J.Samways¹, G.Carchini² and M.Di Domenico²
1 DepartmentofZoologyand Entomology,University ofNatal,
P.O.Box 375, Pietermaritzburg3200, SouthAfrica
2 DipartimentodiBiologia,II Universita di Roma, "Tor-Vergata”,
ViaOrazio Raimondo, 1-00173 Roma, Italy
Received December 12, 1991 /Revised andacceptedJune 3, 1992
The larva isdescribed here forthe first time.More comprehensivedescriptionsof
thepartiallydescribedL.plagiatusandL.tridensarealsogiven.All3spp.areabundant
at varyinglocalitiesintheeastern parts ofNatal, SouthAfrica.Comparisonsarealso
made with larvae ofother African Lestidae.
INTRODUCTION
There are seven species ofLestidae recorded to date in South Africa (SAM-
WAYS, 1992):L. dissimulansFraser, 1955; L. ictericus Gerstaecker, 1869: L.
pallidas Rambur, 1842;L. plagiatus (Burmeister, 1839);L. tridens McLachlan,
1895;L. uncifer Karsch, 1899;L. virgatus (Burmeister, 1839).Few of the larval
stages have been described. L. ictericus was described as ”L. pallidas form
ictericus Gerstaecker 1869” by PINHEY (1961). L. tridens was also described
by PINHEY (1959) and L. plagiatus was described by CAMMAERTS (1966).
Another African species, L. simulans Martin, 1910, was recently described by
LEGRAND (1976) but has not been recorded from SouthAfrica. The larva of
theMalawian,ZambianandZimbabweanspecies. L. ochraceus Selys, 1862was
described as "L. pallidas form ochraceus” by P1NHEY (1959). In due course
thisspecies may wellberecordedinSouthAfrica, aftermoreintensivesearching.
The aim here is to describe the larva ofanotherLestidae species until now
unknown:Lestes virgatus. As the descriptions ofL. tridens andL.plagiatus are
incomplete, wepresentfurtherdataonthelarvalmorphology ofthesetwo species
506 M.J. Samways. G.Carchini & M.Di Domenico
permitting improved comparisons with the other species.
MATERIALAND METHODS
CORBET’s (1953) terminologyfor the labium wasadopted here, althoughit does not strictly
apply tothe Lestidae. Inparticular, the morphologyofthe branches ofthe palpusarenotdescribed
by Corbet,soadditional termswererequiredhere, such asinnerandouterlobes ofthelabialpalpus,
asproposedbyLEGRAND(1976),The descriptionswerefromlarval exuviae ofspecimenscollected
in the field andreared in the laboratory throughtoemergence. Species determinations were from
teneral imagos.Exuviae werestored in 70% ethyl alcohol anddrawn with microscope/cameralucida
<200 x magnification.Allmeasurements weretothenearest0.1 mm, with amicrometric eyepiece.
The followingdimensions were measured. Dorsal view: head width, antennaelength, distance
betweenantennaeinsertionaxes,anteriorwing-sheathlengths(fromthe mutualjunctionpointbetween
left andright ones). Ventral view: prementum width (afterbeingcut at the postmentum level and
laidout,but notflattened),and length (fromthe tipofthe anterior mediallobe tothe articulation
line with the postmentum). Lateral view; caudal gill lengthand metatibial length. The variable
telescopingofthebodyduringpreservation precludedmeasurement eitherofabdomen ortotal body
length.Distortion duringpreservation also affected therelativepositionofthewingcasesand the
abdominalsegments, as wellastheprementum-postmentum articulationandthe coxaepairs.
DESCRIPTIONS OF THE LARVAE
LESTES VIRGATUS(BURMEISTER)
Figures 1-2
Material. - 4 6, Queen ElizabethPark, Pietermaritzburg.Natal. 16-1-1989, 21-1-1989, 13-
X11-I99I; — I S. Himeville, Natal, 30-1-1930; — 2 9, Queen Elizabeth Park, Pietermaritzburg,
Natal, 13-XII-1991.
The larva has not been described previously.
Body long and slender, as is typical ofthe Lestidae. Head wider than the
thorax, withlarge globular eyes. Head width4.0-4.2mm. Antennae7-segmented,
and3rdsegment longest, andthe 4th only less so. Antennaelength 3.2-3.3 mm;
distancebetween insertions 1.3 mm.
Mask clavate, but relatively short and massive, premental articulationat the
level ofthemesocoxae. Prementumlength 3.3-3.4mm, width2.1-2.3 mm, pre-
mentalsetae 6+6, or 5+5, median cleft fairly long, with several spiniform setae
on both sides, alineofspiniform setae on the lateral marginofthe prementum.
Distal marginoftheprementumcrenulate,withone claviformseta oneachcrenu-
lation.
Palpus ofthe usual Lestes type, with one long seta and two similar setae on
themovablehook.Distal marginofthepalpus deeply dividedintotwo branches.
Inner branch ofthe palpus bearing one strong terminalhook and with minute
regular serrations on inner margin,and alsowith alineofsmall spiniform setae.
Outer branch bearing two large unequal-sized hooks, and an intermediateline
Larva ofLestes virgafus 507
Fig. 1. Morphologyofthe larva ofLestes virgatus: (a) wholeview ofthe mask; — (b)prementum
and palpus; — (c)distal marginofthe prementum nearthepalpusarticulation; — (d) distal margin
oftheprementumnearthemediancleft; - (e)innerbranch ofthepalpus,end hookandinnermargin
ofthepalpus.
with irregular teeth, benttowards the innermosthook.
Wing sheaths covering all ofthe 3rd or halfofthe 4th abdominal segment;
anteriorwing sheathslength 5.6-5.7mm. Legs very slender,astypical inLestidae.
Hind femurlength 4.7 mm.
Abdomen slender, all segment surfaces covered by fairly long and slender
setae. Terminal segments with latero-inferiorcarinae, covered by setae little
different in shape and in length to those covering the remaining surface. Last
two segments with a dorsal line of long hair-like setae aligned on the medial
plane. Last segmentwith a deep dorsal incision.
508 M.J. Samways, G.Carchini& M.Di Domenico
Fig.2. Morphologyofthe larvaofLestesvirgatus: (a) lateral lamella; - (b)central lamella; — (c)
last twoabdominal segments.
In thefemales,the gonapophyses are well developed, whichis unusual forthe
larval stage.The apices ofthemedial valves extendedbeyond the epiproct and
paraprocts, whilethoseofthe external valves extendedbeyond thedistalendof
S10.
Caudal lamellaetypical oftheLestidae,withsecondary tracheaeslightlyvisible,
but the main tracheae with some apparent bamboo-like sections with clearly-
marked taenidia(Fig. 2a,b), mainly inthecentrallamella.Pigmented bandrepre-
sentedonly nearthemargins; numeroussmallpigmented spots irregularly spaced
on the surface, but not inproximity ofthemargins. Lateral lamellaelength 7.0-
-7.5 mm, central lamellae length 6.8-7.3 mm. Lateral lamellae slightly longer
than the central one, but in one example the reverse appears to be the case.
Spiniform setaeon thewhole margins ofthe lamellaeand hair-like setae on the
distal half, with similar distributionson the dorsaland ventral margins. Cerci
long and slender.
Larva ofLestes virgalus 509
LESTESTRIDENS McLACHLAN
Figures3-4
Material. — 4 3, I 5,poolsat StLucia, Natal, 11-II-I990; — Id, KratzkopKloof,2-II-
1988; — Id, Stainbank Nature Reserve, Durban, X-1988; — 1 <J, I 9,same locality, 13-1-1992.
Thelarvawas describedby PINHEY(1959),butwithout figuresofthe lamellae
and detailsofthe palpus.
General featuresofthe body, head, legs andlamellaetypical forthe Lestidae.
Headwidth3.8-4.0mm, antennae7- segmented, but inoneexample, one antenna
was 6-segmented; 3rdsegmentthelongest. Antennaelength 2.9-3.3 mm, distance
between insertions 0.9-1.0 mm.
Maskclavate, very slender with the medial part ofthe prementumthin, and
nearly triangular intransverse section. Articulation between the prementumand
the postmentum at the level ofthe metacoxae, but in one specimen slightly
behind.Prementumlength 3.7-4.2mm, width 1.3-1.4mm,premental setae varia-
blein numberand inlength from5|+|5 to 52-h4and to6t+25. Distal margin of
the prementum straight with crenulations, each with one truncate seta on each
crenulation. Some spiniform setae along the lateral margins ofthe prementum
nearthe articulationwith thepalpus.
Palpus as usual in Lestidae, with one long seta andtwo similar setae on the
movable hook. Distal margin of the palpus deeply divided into two branches
Innerbranch bearing one strong and long end-hook, and withregular serrations
on the inner margin, coupled with some small spiniform setae not so numerous
as the serrations. Outer branch of the palpus with two strong unequal length
hooks, andanintermediatelineofsmall irregular teeth,separated fromthelarge
hooks by two concavities on the palpal distal margin.
Wing sheaths covering half of the second or half of the third abdominal
segment,anteriorwing-sheaths length 4.7-4.8mm.Hindfemurlength 4.8-5.4mm.
Abdominal segments covered by spiniform setae. Terminal segments with
latero-inferiorcarinae, covered by setae similar to those covering the otherseg-
ment surfaces. Last two segments with a dorsal lineof long hair-like setae in
themedial plane. Last segmentwith a deep dorsal incision.
In thefemale, the ovipositor did not extend beyond the distalend of S10.
Caudal lamellaeprincipal tracheae with apparentbamboo-like sections. Pig-
mentedareas as inFigure 4;no spots on thesurface. Laterallamellaelength 8.9-
-9.5mm, central lamellaelength 8.7-8.8 mm,about0.5mmofdifferencebetween
thecentralandthelateralonesineachspecimen. Spiniform setae along thewhole
margin ofthelamellae, with theexception ofthevery distalparts; hair-like setae
very scarce, more numerous in thevery distalparts ofthe lamellae.Cerci long
and slender.
510 M.J. Samways, G.Carchini & M. DiDomenico
Fig. 3. Morphologyofthe larva ofLestes tridens: (a) wholeview ofthe mask; — (b) prementum
and palpus; — (c) distal marginoftheprementum nearthe palpusarticulation; - (d) distal margin
oftheprementum nearthemediancleft; - (e)inner branch ofthepalpus,end hookandinner margin
ofthe palpus.
LESTES PLAGIATUS (BURMEISTER)
Material. — I <5.1 9,Hilton, Natal. IX/X-1988;— I 6, HlambojaR„ Drakensberg,Natal,
25-1-1991.
The larvawas described by CAMMAERTS(1966)fromasingle female(without
antennae), collectedin 1933,in Elisabethville, Belgian Congo (Zaire).
Our specimens are almost identical tothatofCammaerts. We report here on
some additionalrelevant data:
Antennae7-segmented, thethird segmentthelongest, antennae length 3.9-4.5
mm, distancebetween insertions 1.2-1.3mm.
Maskclavate, prementumlength 3.9-4.1 mm,width 1.6-1.8mm. Nospiniform
Larva ofLe.iles virgatus 511
Fig.4. Morphologyofthe larva ofLestestridens:(a) lateral lamella; — (b) central lamella; — (c)
last two abdominalsegments.
seta on the palpus nearthe articulationofthe movable hook.
Wing sheaths covering allofthe3rdabdominalsegment,anteriorwing sheaths
length 5.3 mm. Hind femurlength 5.3-6.1 mm, tibia4.9-S.4 mm, tarsus 1.9-2.1
mm.
The ovipositor of the female reached just the end of S10. Lamellae length
10.0-10.7mm,lateral and central lamellaealmost equal in length.
DISCUSSION
Atthis stageinour knowledge, itis not possible to give acomprehensive key
forall the SouthAfrican Lestidae larvae, owing tothecomplete absenceof data
512 M.J. Samways, G. Carchini& M. Di Domenico
forthreespecies: L. dissimulans,L.pallidus andL. uncifer. However,some initial
comparison is possible for the most common species occurring in the eastern
part ofthe country.
L. virgatus is quitedifferentfromthe otherspecies intheshape ofthepremen-
tum. Incidentally, however, in this character, it is similar to the Palaeartic L.
macrostigma. Also the pigmentation in virgatus, with numerous small spots, is
quite unique in the species covered here, but caution is necessary as this may
be a variablefeature across a wide distributionalrange. These two characters
alone,nevertheless, distinguishthis species fromtridens,plagiatus and simulans,
and in thefemales the length ofthe ovipositor was also highly diagnostic.
L.plagiatus inturn, has characteristic outerbranch of the palpus, withoutthe
intermediateline ofteethbetween the terminal hooks. This character, together
with the shape and the length ofthecaudal lamellaedistinguishes this species
from theother three species.
L. simulans is similar toL. tridens inthe morphology ofthe mask, palpus and
lamellae. However, the numberof the premental setae is different.L. simulans
has 10setae,andL. tridens 12-14,making thischaracterusefulfordistinguishing
these two species, especially where theirrangesoverlap in East Africa.
PINHEY’s (1959, 1961) descriptions of L. pallidus form ictericus and L.
pallidus form ochraceus do not refer to the shape, or the length/width ratio of
theprementum,buthementions’’mask reaching slightly beyond bases ofmiddle
legs” forL.ictericusand ’’labiumreaching secondpairoflegs”forL. ochraceus.
So, atthisstage,wecannot excludethepossibilitythat ictericusand/orochraceus
also have a short mask as does L. virgatus. Moreover, the morphology of the
lamellaewas not reported for L. ochraceus andthemorphology ofthe palpus is
notclearly figured forictericus(PINHEY,1961).Thelamellaeapices ofictericus
was reported by PINHEY (1961) to be similar to those of tridens, while the
illustrationof the palpus ofochraceus shows an outer branch similar to that of
plagiatus. At the present time, therefore, it is not possible to discriminate the
larvaeofL. ochraceus and L. ictericus fromthe other known larvae.
ACKNOWLEDGEMENTS
Weacknowledgefinancial supportfromtheItalianMinistryofUniversity and Scientific Research,
Programma"Popolamentoanimale delMediterraneooccidentale”(toG.C.), andthe Foundation for
Research Developmentand theUniversity ofNatalResearch Fund(toM.S.).The NatalParksBoard
kindly provided accessto sites, and Mrs JANEFLOCKHART and Ms PAMELA SWEET kindly
processed the manuscript.
REFERENCES
CAMMAERTS, R., 1966. La nymphede Lestesplagiatus (Burnt., 1839).Revue Zooi Bat.afr. 74;
317-323.
Larva ofLestes virgatus 513
CORBET, P.S., 1953. Aterminologyforthe labium oflarval Odonata. Entomologist86; 191-196.
LEGRAND,J„ 1976.Apropos deLestes simulans Martin 1910:larvaeetimago(Zygoptera;Lestidae).
Odonalologica5: 375-381.
PINHEY,E„ 1959, Notes onAfrican Odonatanymphs (I). J.enl. Soc.sth. Afr.22: 469-4X8.
PINHEY, E., 1961. Notes onAfrican Odonatanymphs (2). J. ent.Soc.sth. Afr. 24: 165-172.
PINHEY, E.,1984. Asurvey ofthe dragonflies(Odonata)ofSouth Africa.Part I. J.ent.Soc. sth.
Afr.47: 147-188.
SAMWAYS,M.J., 1992. Dragonflyconservation in South Africa: a biogeographical perspective.
Odonatologica21(2): 165-180.