Harmsen,R.

Jabbal,I.

Biodiversity Heritage Library OAI Repository

Page 141
CURCULIONIDAE (WEEVILS) OF THE
ALPINE ZONE OF MOUNT KENYA
(Resultsof theUniversityCollegeNairobi Mount Kenya Expeditionof March 1966-
Publication1)
I. JABBAL
(ZoologyDepartment,UniversityCollege,Nairobi)
R. HARMSEN
·Presentlyat Universityof Toronto,Toronto, Ontario,Canada.
INTRODUCTION
In March 1966,a numberof biologistsof UniversityCollege,Nairobi,underthe
leadershipof Dr. MalcolmJ. Coe,undertooka researchexpeditiontothealpinezone
of MountKenya.Themainpurposeof theexpeditionwasto studytheecologyof the
relativelydrynorthernslopesof MountKenyawhich,froma biologicalstandpoint,
werevirtuallyunknown.TheBaseCampwaserectedat 12,500ft. (3,800m.) in the
KazitaWestValley.Most workwascarriedout in thevicinityof thecamp,buta
numberof collectionsweremadeupto theheadof thevalley(c. 14,000ft.---4,300m).
Thevegetationin thisregionis fairlytypicalof theloweralpinezone:consisting
mainlyof opentussockgrasslandandpatchesof Carex monostachyaA. Rich.bogon
drainageimpededsoils.Collectionsweremadein thefollowingsituations:
1.FestucaabyssinicaSt-YvesandF. pilgeri A. Rich.tussocks.
2. Lobelia keniensisR.E. Fr. & Th. Fr. jr. rosettesandinflorescences.
3.Opensoilandrockyground.
RESULTS
OccurrenceandDistribution
Appendix1 includesall thespeciesof Curculionidaeso far recordedfromthe
moorlandandalpinezonesof MountKenya(9,oooft.-14,900ft.or2,700m.-4,500m.).
Thisinformationhasbeenderivedfromourowncollectionandtheoneof theNational
MuseumofKenyaaswellasfromasurveyofthemainrelevantworksintheliterature:
A. Hustache(1929)andS. Schenkling(1934).
Ecology
Onlyfivespecieswerefoundto beof someecologicalimportanceitherbecause
of theirabundanceor asa resultof a particularpositionin a foodchainor microha-
bitat.Otherspeciesmaywellhavesuchimportancein othertimesof theyearor in
othermicrohabitats,asyetundiscovered.Theonesof obviousecologicalimportance
asdiscoveredsofarare:
1.ParasystateselongatusHust.
2. Cossonusfrigidus Hust.
3. SeneciobiusbasirufusMshl.
4. AmphitemetisulcipennisMshl.
5. Afrotroglorrhynchus(nivalis?)Hust.
The followingecologicaldatawerecollectedfor theabovelistedspecies:
1.ParasystateselongatusMshl. (Plates1-3)
A numberof adultsof thisspecieswerecollected(fromopensoil in Festucatussockareas)during
day timewhenweatherconditionsalloweddispersalandmatingactivity(air temperaturel2°C and
directsolarradiation).
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Duringa studyof theFestueatussockasanecologicalmicrohabitat,matureandimmatureadults
aswellas larvaeandpupaeof thisspecieswerecollectedfromF. abyssinieatussocks.The specimens
werefoundin chambersproducedby thelarvain theregionof thetussockjust abovethestembases.
Themainmatrixof thisregionconsistsof semi-decayed,eadFestuealeavesandis penetratedby the
living stemsof thegrass.The beetlelarva appearsto feedon thelowerportionsof the live stems,
but mayderivesomenutritionfrom thedeadmatteraswell.Pupationtakesplacein thechambers
andtheadultemergesandmaturesthereaswell.
The amountof damagedonebyParasystatesto theFestlleatussocksis verylimitedbecauseof the
relativerarityof thespecies.It is,however,potentiallya tussockkiller becauseof itsmodeof feeding.
This specieswas mainly found in F. abyssiniea,but appearedto be uncommonin F. pilgeri;
whetherthis reflectsa highlyselectivehostspecificityor a habitatpreferenceis not known.Within
the tussock,the placingof the chamberdoesreflecta very sensitivemicrohabitatselection.The
chambersareneverin thewaterloggedregionof thetussockbelowthestem-baseandneverin the
dry upperregion.Theregionin whichthechambersarefoundprovidesmaximumprotectionagainst
drowning,fire,andpredators.This extentof safetyto thelarvaeandpupaemakesthisspeciespoten-
tiallyan "outbreak"specieswhich,undercertainconditions,couldseverelydamagetheF.abyssiniea
coverresultingin considerablechangesin theecomorphologyof thealpinezone.
2. CossonusfrigidusHust. (Plates4-7)
The larvaeandpupaeof thisspecieswerefoundin verylargenumbersin theinsideof thehollow,
recentlydied,woodyregionsof therachisof Lobeliakeniensis.Here,theyappearedto form a major
factorin thedisintegrationof thesestructures.They wereneverencounteredin living specimensof
Lobelia,nor in thedead"leaf frills" belowtheliving rosette;this,possibly,becauseof themoreor
lessanoxicconditionsof thesehabitats.The adultsemergein thedeadrachisandmustthenundertake
a periodof dispersalandmating.No freemovingspecimenswerecollected,but a numberof mature
adultswerefoundin Lobeliainflorescences.It seemsprobablethattheadultsareattractedto thesein-
florescencesafter dispersaland that theyremainstationaryhereuntil the floweringperiod of the
Lobeliaendsandovipositiontakesplace.
This speciesobviouslydoesnot harmthestandingvegetationin anyway,andis, therefore,of no
influenceon thevegetationcompositionand successionof thealpinezone.The larvaeare subject
to predationby a numberof predatorystaphilinidlarvaewhichalsoinhabitthedeadLobeliarachis.
There is a further,and perhapsmoresevere,predationat the time of adult concentrationon the
Lobeliainflorescenceby anumberof insectivorousongbirds.In particulartheHillchat(Pinaroehroa
sordidaearnestiSharpe)and the ScarletTufted MalachiteSunbird (Neetariniaj. johnstoniShelley)
wereregularlyobservedfeedingon theinsectsin theLobeliainflorescence.
3. SeneeiobiusbasirufusMshl. (Plate8)
Mature,adultspecimensof thisattractivelycolouredbeetlewerecollectedfromtussockgrassland
and from amongrockson open,frost heavedsoil. Theyappearedquitelethargicwhentheair tem-
peraturewaslow but as soonas it becamewarmtheyshowedconsiderableactivity.Someof them
werecaughtwalking,but no matingwasobserved.One specimenwascollectedat 14,000'altitude
in a completelymoribundstateunder deadvegetablelitter on a cold, cloudy morning(air temp.
±3°C in shadyareas).
Of thisspecies,neitherlarvaenor pupaewereencountered.
Becauseof its considerablesize(16.5mm.)and its local abundance,this speciescould form a
significantpercentageof thefood of certainmammalsor largerbirds.Augur Buzzards(Buteorufo-
fuseusaugurRupp.) wereoftenobservedcatchingbeetlesand hundredsof beetleelytrawerefound
in buzzardpellets;noneof these,however,belongedto S. basirufus.It is possiblethatthespeciesis
poisonousor distasteful,a situationoftenfoundin brightlycoloured,slowmovinganimals.
4. AmphitemetussulcipennisHust. (Plate9)
The adultsof thisspecieswerealsocollectedfromamongrockson opensoil andfrompatchesof
vegetationmainly consistingof Festueatussocksand Alehemillacover.Considerableactivity, in-
cludingmating,wasobservedas soonas theweatherbecamewarm: i.e. air temperature12°Cand
directsolarradiation.This beetlewasquitecommonin certainareasandcouldconstitutea major
sourceof proteinnutritionfor largerbirdsandsuchmammalsasshrewsand insectivorousrodents
(e.g.Lophuromys).No directevidenceof suchpredationis available,and Augur Buzzardpellets
did not containAmphitemetuselytra.This maybebecauseof theexcellentcamouflageof theseslow
movingbeetles.Another reasoncould be that thebuzzardsfind it uneconomicalto feedon these
small beetleswhenthereare a largenumberof rodents,shrewsand largerbeetlesavailable.The
beetle's"freezing"behaviourin thepresenceof humanbeingssuggeststhatpredationis a mortality
factorof somesignificance.
5. Afrotroglorrhynehus(nivalis?)Hust.
Only twospecimensof thebeetlebelongingto thegenusAfrotroglorrhynehuswerecollectedwhile
beatingAlehemillajohnstoniiOliv. This specieseemsto beverynearA. nivalisHust., butaccording
Page 143
to Dr. Edward Voss'" it could be a differentspecies.Jabbal (1968)is at presentin theprocessof
describingit as a new species,Afrotroglorrhynchuskazitae.Sincethis beetleis of relativelysmall
size(4.8mm.)andnot verycommon,it is probablyof no quantitativeecologicalimportance.
DISCUSSION
The unique featureof Mro-montane regionsis their remarkablediurnal temperaturerange,
underwhoseinfluencean animalmay be submittedto sub-zeroeverynight and intenseheatand
low humidityduring the day. Hedberg(1957)calledthis typeof climate"winter everynightand
summereveryday".Therelativehumidity,whichin theseregionsfluctuatesdailywiththetemperature
andcloudcover,hasbeendescribedby Coe(1967):"at groundleveltherelativehumidityjust before
sunrisewas 90%, whenthesun rosethis figurefell within about90 minutesto below20%; when
during thecourseof the day thesun becameobscuredby cloud, the figureroseto 80%". In such
a climatewith largeand regulardiurnal temperaturechangesit is not so muchthe extremes,but
ratherthespeedwith whichtheyfluctuate,thatis themaincontrollingfactoron insectlife.
Theatmospherebecomesthinnerasthealtitudeincreases,thusresultinginlesserheatingoftheair
duringthepassageof solarradiation.The mostimportantcomponentof this incomingradiationis
the ultraviolet.While consideringthe climatenear the ground Geiger (1950)quotesthework of
Maurer,who found thattheamountby whichgroundtemperaturexceedsthatof theair increases
with altitude,a factor of obviouslygreatsignificanceto microclimatein theequatorialmountains.
During theday theoutwardradiationfrom thegroundand vegetationis not veryapparentbut at
high altitudesits effectis of greatimportanceas an additionalcoolingagentat the surfaceand
in consequencethiseffectmaybestronglyfeltby theinvertebratesoccupyingthemicrohabitats.The
suddenloweringof temperaturedoes not, however,penetratemore thana fewinchesbelowthe,
surfaceof thesoil-4 to 6 inchesbelowthegroundlevel,thetemperaturewasfoundto bec6°C.So
in largepart, theprotectiveinsulatingmechanismsthathavebeendevelopedby thevegetationare
fully utilizedby theinvertebratefauna.
The activityof insectsin suchareasis greatlylimitedandseemsto takeplacein burstsof short
durationwhenevercircumstancesarefavourable.At nightthe intensecold rendersthemincapable
of movement,whileduringtheday,exceptfor a shortperiodaftersunriseandjust beforesunset,the
groundtemperatureis far too highandhumiditytoo low. Thus, not surprisingly,it is dueto these
two factorsthat a high percentageof arthropodsexhibitssedentaryand cryptozoic habits,which
keep themwithin or closeto thecomparativelyconstantmicroclimateof theirshelters.Examples
of thisareCossonusin theLobeliarachisandParasystatesin theFestucatussock.Noneof theobserved
speciesshowedanyevidenceof rhythmiccontroloveractivity.
Morphologicalfactorsseemto play an importantrole in theadaptationof invertebratelife to
the alpineclimate.The highly reflectivesurfaceof someof thebeetleslike Parasystateselongatus
is probablya meansof protectionagainstradiation.The predominantlydark coloursof almostall
theweevilscollectedcouldbeimportantin heatabsorption.It is probablyan advantageto absorb
heatquicklyin theearlymorning,so thattheanimalcancompleteits mainperiodof activitybefore
thegroundbecomestoohot.All theCurculionidscollectedpossessinflatedelytrawhoseenclosedair
could havean importantinsulatingfunction.
Onepointof evolutionaryinterestis thefusionof theelytraandabsenceof wingsin mostof the
alpineCurculionids.This apteryor brachypteryis a commonphenomenonof highaltitudeinsects
andMani (1962)suggeststheobviousselectiveadvantageof suchamodification.He pointsoutthata
flyinginsectcaneasilybecarriedbyup-currentsonthebarrenpeakregionorsweptoff themountain
altogether.The windson East African mountains,however,arenotgenerallyasstrongasthoseon
theHimalayas.Thus,whetherthepresenceof flightlessinsectsonMount Kenyarepresentsaselective
survivalof apterousspecieswhichhavecolonizedthemountainor whetherit representstheevolu-
tion of apterousspeciesfromnormal,wingedspeciesaftercolonizationof themountainis verymuch
a matterof speculation.
During theMarch 1966expedition,no attemptwasmadeto collectthesmallerspeciesof the
family Curculionidae.Yet, of the thirty two previouslydescribedspeciesfor Mount Kenya four
were encountered,and one new specieswas found (Afrolroglorrhynchuskazitaen. sp.). This in-
dicatesthat a systematicsurveyof the alpineregionsof Mount Kenya will probablyuncovera
considerablenumberof weevilsasyetundescribed.
The purposeof this expeditionwas to studythe ecologyof the northernslopesof the alpine
zoneof Mount Kenya.The work on Curculionidaeasreportedabovethrowssomelighton therole
playedby thelargerandmoreabundantspeciesof this family in biologicalinterrelationships.The
rarerandsmallerspeciesmustalsoplaysomerole in theecologyof thisregion.At presentthisrole
seemsto beof littlequantitativeimportance,however,it requiresa closerstudy.
"'Dr. EdwardVoss of 4501Hardenberg,Am Boberg2, B. R. Deutschland,kindly examinedour
specimens.
E
Page 144
ACKNOWLEDGEMENTS
The authorswould like to expresstheirgratitudeto theDirector of the Kenya National Parks
and to Mr. BiU Woodleyfor their co-operation.The work wassupportedby a Ford Foundation
grantfor Ecologicalresearchto theZoologyDepartmentof UniversityCoIlege,Nairobi.
BIBLIOGRAPHY
1. CoB,M. J. (1967),The Ecologyof theAlpine Zone of Mount Kenya. 134pp. 20 figs., 24 pI.
Junk. Hague.
2. GEIGBR.R. (1950),The ClimateneartheGround. pp. xxi+482.Harvard.
3. HEDBERG,O. (1957),Afro-Alpine vascularplants.Symh.Bot. Upsal.151:1-411.
4. HUSTACHE,A. (1929),Voyagede Ch. AIluaud et R. JeannelenAfrique Orientale,Resultants
Scientifiques:InsectesColeopteres.19:367-560.
5. JABBAL,I. (1968),A Descriptionof Afrotroglorrhynchuskazitaen. sp. in.ed.-MS.
6. MANt,M. S. (1962),Introductionto High AltitudeEntomology.London.
7. SCHENKLING,S. (1934),Coleopterorumcatalogueauspiciiset auxi/io, W. Junk, 28, 29 & 30.
Page 145
APPENDIX I
CHECKLIST OF CURCULIONIDAE COLLECTED FROM TRE MOORLAND AND ALPINE
ZONES OF MOUNT KENYA
All thenamesmarked*arein thecollectionof theNationalMuseumof Kenya.
Name Authority
A. Subfamily:Otiorrhinchinae
1.Amphitemetus
griseusRust.
2. *A. sulcipennisRust.
3.Leptospyris
sylvaticusRust.
4. L. glacialisRust.
5.L. laevisRust.
6.Parasystates
albovittatusAuriv.
7. *P. elongatusRust.
8.P. alternansRust.
9.P. nigripennisRust.
10.P. alpinusRust.
11.P. brunneusRust.
12. SystateselongatusRust.
13. Barypeithes
microphthalmusRust.
14. Omias(Neomias)
kenyaeRust.
15. O. (Neomias)
kenyaevar.
glacialisRust.
16. O. (Neomias)
alpinusRust.
B. Subfamily:Cleonidae
17.Lixus nycterophorus
var.kenyaeRust.
18. *L. alpinusRust.
CollectorandDate Altitude
Alluaud & Jeannel
9,200ft. and
1912
10,5 0ft.
Alluaud & Jeannel
9 2 ft. and
1912Joy PeterBallyNov. 1943 Mrs. BallyJan. 1964 Jabbal &Rarmsen
2
March 1966 Alluaud & Jeannel
,3 14 4
ll Jea el
7 9
. J. F. GedyeDec use mSt ff
5
47 F. C. Delkirk
8
F b 50 Rarmsen& J bbaJ,66
-1 -ft.-0
10,500ft.
Alluaud & Jeannel
Alluaud & Jeannel
8
Mrs. Bally
References
Rustache(1929)
pp.384-385.
Rustach(1929)
pp. 385-387.
Rustacl>e(1929)
pp.401~02.
Rustache(1929)
pp. 402-403.
Rustache(1929)
pp. 403-404.
Rustache(1929)
p.406.
Rustache(1929)
pp. 407-408.
Rustache(1929)
pp. 408-409.
Rustache(1929)
pp.410-411.
Rustache(1929)
pp. 413-414.
Rustache(1929)
pp. 414-415.
Rustache(1929)
pp. 424-425.
Rustache(1929)
pp. 450-451.
Rustache(1929)
pp.451-452.
Rustache(1929)
p.452.
Rustache(1929)
pp.452-457.
Rustache(1929)
p.474.
Rustache(1929)
p.475.
Page 146
NameAuthority
Col/ectorandDateAltitudeReferenc s
19.• L. adspersusBoh.
Mrs. BallyBoheman(1871)
Jan. 1944
Fa rs. Oefrers.
Vet. Akad. Forh.18: 58,230.C. Subfamily:Rhyparosominae 20. ·Oreoscotus
Alluaud & Jeannel10,800ft.Hustache(1929)
fulvitarsusHust.
19121 5pp. 465-466.
A. J. F. Gedye
0
Dec. 1934 MuseumStaff
2 15
Jan. 1947 rs BallyD. Subfamily:Eirrhininae 1 Homoedenodema
d & Jean el9,2Hustache(1929)
aHust.
83 84
E. Subfamily:Apioninae
2. Apionwaren orffiWagner
M m. Soc. Ent
1912
elg. 19: 41.
F. fa ily:Baridinae 3 BariskenyaeHust.
00531 533
G. f il :Cossoninae 4 Mi u glacialisHust.
11u ud9,4 ft. pp. 544-545.
25. ·Cosson (or
l e
Afrocos on )
7 f4 4
hyperboreusHust. MuseumStaff26.C. dorytomoidesHust.
547- 48
7 ./rigid
4 49 50
MuseumStaff
v.Zoo/.B t
Jan. 1947
Afr. ( 3 )
26:
36.
A. J. F Gedye Jabbal &H rmsenMarch 19668. · . ( r Pseudo-mes te )glacialisHust.
52
Dec. 1934 .36.
H. Subfa ily:Otiorrhinchinae 9 ·Seneci biusbasirufusMshl.
. llJ. E. Afr,Nat.
Aug 1934
Hist. Soc. (1950).
9, : 147rs Bally
(Received30thJanuary 1968)
NameAuthority
30.·S. semi/ucensMshl.
31.·Strictoseneciobius
ebininusHust.
32. ·SeneciobiusloveniAur.
or granulipennisHust.
CollectorandDate
A. K. Hading
1949
Mrs. Bally
1944
A. K. Hading
1949
Altitude
11,000ft.
10,500ft.
13,000ft.
Page 147
References
J. E.A. Nat. Hist.
Soc. (1950).
19, 5:147
Ann. Mag. Nat.
Hist. London
(1940).(11)
13:93-98
Rev.Zool. Bot.
Afr. (1923)11188.
Ann. Mag. Nat.
Hist. (1934).(10)
15:503
4 mm.
ParasystateselongatusRust.
Page 149
lmm.
Mouth partsof thelarvaof Parasystateselongatus
Page 150
4mm.
Larva of Parasystateselongatu~'
2 mm.
COSSOIiUSfrigidus Bust.
1mm.
Mouth partsof thelarvalof Cossonusfrigidus.
Page 151
2mm.
Larva of Cossonus[rigidus.
2 mm.
Pupa of Cossonus[rigidus.
4 mm.
SeneciobiusbasirufusMshl.
Page ]54
I 4mm. I
AmphitemetusulcipennisRust.


Curculionidae (weevils) of the alpine zone of mount Kenya

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Curculionidae (weevils) of the alpine zone of mount Kenya

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