Distribution, Abundance and Phenology of Scaptomyza (Bunostoma) anomala Hardy (Diptera: Drosophilidae): a Proposed Representative Species for Monitoring Protein Bait Sprays in Hawai'i

13 Pages·1993·0.67 MB·

by  Asquith, A

69
Distribution, Abundance and Phenology ofScaptomyza
(Bunostoma) anomala Hardy (Diptera: Drosophilidae):
a Proposed Representative Species for Monitoring Protein
Bait Sprays in Hawai'i
ADAMASQUITH1
DepartmentofEntomology,UniversityofHawaii,KauaiResearchStation,7370Kuamo'oRd.,
Kapa'a,Hawai'i96746,USA
ABSTRACT. The endemic Hawaiiandrosophilid Scaptomyza (Bunosloma)anomala is
proposed as a representative native species for monitoring the effects of protein bait
spraysagainstpestTephritidaeinHawai'i.Thisspeciesisstronglyattractedtoproteinbait
andis foundon severaldifferentislands. On Kaua'i,itoccursfromsealevel toat least
1200melevationandcanbefoundinareasofbothnativeandalienvegetation. Insome
areasthisspeciesdisplaysdistinctseasonal fluctuations inabundance, whichvary with
elevationandhabitat.Flyabundancevariedsignificantlybothamongandwithinsampling
sites,withabundanceusuallyrelatedtotheamountofshade,buttherelationshipvarying
withelevationandhabitat.Itissuggestedthatamonitoringsystemforthisspeciesemploy
multipletrapsineachofseveralpairedtreatmentandcontrolsites,withaminimumof1
yearpretreatmentand I yearpostireatmentdatacollection.
INTRODUCTION
Perhapsthemostcontroversialaspectofpest lephritideradication/control inHawai'i
isthe possiblenegativeeffecton theunique native insectfauna (Howarth 1990, USDA-
APHIS 1985).The widespread application ofbaitspraysisconsideredparticularlyques
tionable due to its non-specificity and therefore the potentially diverse nontarget effect
(Beardsley 1990,Asquith & Messing 1992). Although recenteradication strategieshave
emphasized more environmentally benign techniques such as sterile insect releases
(Lanceetal. 1992),notevenincipientinfestationsoftheMediterraneanfruitfly,Ceratitis
capitata(Wiedemann),havebeensuccessfullyeradicatedwithsterileinsectsalone,much
lessestablished populations such asthose in Hawai'i.Therefore, it is likely thatany full
scaleeradication programinHawai'i wouldeitherplanfor(Harrisetal. 1986),orhaveto
resortto(Jackson& Lee 1985)baitsprays,at leasttoreducehighpopulationsinagricul
tural areas.
Despiteconcernsregardingbaitsprays,almostallavailableenvironmentaldataarefor
pests, predators or parasitoids in agricultural systems. Only during the 1980-1982 Ca
liforniaMediterranean fruit fly eradication program were nonagricultural systems moni
tored. Directkilloflarval Lepidopterawasdocumented(Troetschler 1983)andapopula
tion surge of a native gall midge (Diptera: Cecidomyiidae) was observed, presumably
resulting from bait spray-induced mortality ofits parasitoids (Ehlcrct al. 1984). In the
onlynon-agriculturalstudyofpotentialbaitsprayimpactsinHawai'i,Asquith&Messing
(1992) found at least 11 species of native litier arthropods that are attracted to protein
hydrolysate bait.Thesestudies demonstrateaclearpotential foran impactonthe native
Hawaiian insect fauna and suggestthat moredetailedinformationonsusceptiblespecies
shouldbeevaluatedbeforeimplementinga largebaitsprayprogram.
Justasapestfruitflyeradicationorsuppressionprogramwouldbeevaluatedbycom
paring pre- and post-treatment pest numbers, assessmentoftheenvironmentaleffectsof
suchaprogramshouldbebasedoncomparabledatafornativespecies.Althoughonecan
notforeseewhichofthethousandsofHawaiianendemicspeciesmaybeaffected,itwould
beimpossibletoevaluatetheimpactonall speciesandprobablyimpracticaltoimensive-
I.Presentaddress:U.S.FishandWildlifeService.PacificIslandsOffice,Honolulu.Hawai'i96813.USA.
70 Proceedings ofthe Hawaiian Entomological Society Vol. 32
ly monitoreven 20 or 30. A more pragmatic approach is to select a few representative
species likely tobeaffectedbybaitspraysandthatcanbequantitatively monitored.
AssuggestedbyAsquith&Messing(1992),thedrosophilidScaptomyza{Bunostoma)
anomalaHardyislikelytobeasusceptiblespeciessinceitisstronglyattractedtoprotein
bait. Unlike most Hawaiian Drosophilidae, which are usually single island endemics, 5.
anomalaisfoundon Kaua'i, Maui and Lana'i,andwhatisprobablyitsecologicalequiv
alent,Scaptomyzavarifmns(Grimshaw),occursonO'ahu(Hardy 1965).Thismeansthat
thesamespecies andtechniquecouldbeusedformonitoringondifferentislands.
The objective ofthis paper is to promote the use ofS. anomala as a representative
species forenvironmental assessmentoflarge bait spray programs in Hawai'i. Towards
this goal, I provide suggestions formonitoring techniques, and present baselinedata on
thedistribution,seasonalphenologyandabundanceofthisspeciesontheislandofKaua'i.
MATERIALSANDMETHODS
Scaptomyza anomala was sampled using pitfall traps consisting of 500-ml plastic
cups, with asmaller 120-ml cup in the bottom Tilled with ethyleneglycol as apreserva
tive. Aplastic funnel wasalso fit insidethe largercup, rims flush witheachother, and a
round,20cmdiameterplasticraincoversupportedbynailswasplacedca.5cmovereach
trap. The funnel and the surrounding ground within a 10 cm radius of the trap were
sprayed with protein bait (NuLure®, MillerChemical & FertilizerCorp., Hannover, PA)
fromahandheldapplicator.Trapsthatwereburiedtothelipoftencaughtenormousnum
bersofamphipodsorisopods,makingitdifficulttosortthesample.Trapsburiedwiththe
lips2-3cmabovethegroundeliminatedthisproblembutdidnotaffectflycaptures.The
contentsoftraps werecollectedand trapsrebaitedweeklyorbiweekly.
Eighteen different localities covering a variety ofhabitats and elevations were sam
pledon Kaua'i (Table 1).Thenumberoftrapsandtrappingperiodsvariedamong locali
ties,but2stations,AlexanderReservoirand theAlaka'i.weresampled for 1 and 2years
respectively, to assess the seasonal phenology ofthe fly. The relationships between fly
abundance and monthly rainfall and temperature at these sites were examined with
Pearson'scorrelationanalysis.Alsoatthese2 locations,themicrohabitatofeachtrapwas
recorded by qualitatively assessing 4 variables: 1) amount of leaf litter; 2) amount of
shade; 3)amountofdirectsun;and4)soilmoisture.Foreach trap, variableswerescored
onascaleof0-3 (e.g.,0=no leaflitter; 3= 100%).Therelationshipbetweenthesevari
ablesand flyabundancewasanalyzed usingSpearman'sRankCorrelation.
Variation in fly capturesamongtraps wasexaminedbyone-way analysisofvariance
(ANOVA)andmeanswereseparated usingDuncan'smultiplerangetest.
RESULTSANDDISCUSSION
Elevationaland HabitatDistribution
Scaptomyzaanomalamay bethemostubiquitousspeciesofnativeDrosophilidaeon
Kaua'i, as it was collected from almost sea level to 1200m (Table 1). Despite intensive
efforts to collect larvae and rear adults from substrates, the larval habitat was undeter
mined. However, thisspecies does not appearto besubstrate specificas aremanyother
native Hawaiian Drosophilidae (Heed 1968). It was collected from wet Metrosiderosl
Cheirodendron rain forest, uluhe fern thickets with no tree canopy, strawberry guava
monostands, Eucalyptus forest, Scltinus/Lantana pasture, and dry LeucaenalPanicum
shrubland (Table 1). The leaf litter at each site was derived from the dominant cover.
Although the highest numbers (> 1.5/trap/day) were trapped in the wet forest of the
Alaka'i,similarly high numbers (> I.O/trap/day) wereobserved in the mesicAcaciakoa
Asquith: Scaptomyza anomalaas Bait Spray Monitor 71
Table 1.SamplinglocalitiesforScaptomyzaanomalaonKaua'i.
Sampling
Period No.of Rainfall Present(P)
Location (mos.) traps (cm/yr) Elev.(m) Vegetation Abscnl(A)
Moloa'a 2 10 125 150 Psidiumguajavum. A
Psidiumcallleianum
Waikoko 1 10 350 340 P. callleianum,Metro- P
sideros,uluhefem
Powerlinc 2 5 250 180 P. callleianum,Sclunus P
Kaukaopua 3 5 250 100 Acaciakoa,Melaleuca P
Hanakapi'ai
lowersite 2 3 150 10 Mangifera,P.catlle- P
ianum
middlesite 2 3 165 120 P.guajavum P
uppersite 2 4 175 210 Aleurites,P.guajavum P
Kalaheo 2 to 125 150 cultivatedcoffee A
Makaha 2 5 100 900 Acaciakoa.Slyphelia P
Waimea
site 1 1 5 100 1000 Acaciakoa,P.callle P
ianum
site2 1 5 90 600 Scliinus,P.guajavum P
site3 2 5 60 300 Leucaena,Panicum P
PlumTrail 2 10 250 1200 Melrosideros,Cryptomeria P
Alaka'i 24 10 350 1200 Melrosideros,Cheiro- P
dendron,Melicope
Alexander
Reservoir
site 1 12 5 130 160 Schinus,Lantana,Syzygium P
cumini
site2 12 5 130 300 Eucalyptus P
site3 12 5 160 425 Eucalyptus,P.cattleianum P
site4 12 5 200 510 P.callleianum,Metro- P
sideros,uluhefern
foreston MakahaRidge,andtheSchinuslLantanapastureattheAlexanderReservoir 160
msite.
The only sites where S. anomala was not found were the 2 agriculture areas, in the
KalaheocoffeefieldandMoloa'a.Thusitsdistributiondoesnotseemtobelimitedbyele
vationorrainfall,butit maybeexcluded fromareas thathaveexperiencedrecentorfre
quent disturbance, although Hardy(1965) even reported it from a Maui pineapple field.
Thediscoveryof5.anomalainlowelevation,non-nativehabitataddstotheobservations
ofMontgomery (1975). He found that some Drosophilidae may not beparticularly sus
ceptibletoalien predatorssuchasthebig-headedant (PheidolemegacephalaFabricius),
andthattheyconstitutepartofasmall nativefaunathathasremainedin(orrecolonired)
disturbed, lowlandareas(Asquith&Messing 1993).
The wideoccurrenceofthis species lendsanobviousadvantageto using itas arep
resentative,sincesitesformonitoringitspresencedonotneedtobelocatedinnativehabi
tats,butcouldbeselected based largelyonaccessibility,securityandconvenience.These
areimportantfactorsinthemaintenanceoflong-termmonitoring. Inaddition,thisspecies
occurs in, or adjacent to, areas that could conceivably receive bait spray treatments.
CoffeeisnowtheprimaryhostfortheMediterraneanfruitflyonKaua'i;Hanakapi'aiand
similarvalleyshaveextensiveferalcoffee,andthelowerAlexanderReservoirsiteiswith-
72 Proceedings ofthe Hawaiian Entomological SocietyVol.32
1a
Seasonal phenology of S. anomala abundance
Alakai
■I'l'l'l'l'l'l'l1
.My. .Jn. JI.Ag. .Oc.Dc.Ja. . Ma. . My. Jn . Jl . Ag. . Oc
Sampling Date
Fig. la. Seasonal changes in Scaptomyza anomala abundance in the Alaka'i Swamp on Kaua'i.
VerticalbarsarcSE.
in0.S kmofcultivatedcoffeefields.
Seasonality
Fly populations at theAlaka'i siteshowed strong seasonality, with numbers peaking
fromJunetoSeptemberinbothyears,andtheflyessentiallydisappearingfromNovember
toApril(Fig. la).Thispeak wasnegativelycorrelatedwithaveragemonthlyrainfalland
positivelycorrelated withaveragemonthlytemperature(Fig. lb,Table2).Althoughcor
relations were significantly negative, abundance corresponded poorly with the actual
monthly rainfall, so that no obvious changes in fly numbers occurred with particularly
high orlow precipitation.Thisisprobably becausethehumidity in theunderstoryofthe
rainforest is constantly high and largely independent of daily rainfall (Craddock &
Johnson 1981). These distinct, yearly oscillations in adult numbers suggest a life cycle
tiedto thepredictableseasonalchanges in rainfall andtemperature,andnotafacultative
responsetoshortterm weathervacillations.
Seasonal phenology atAlexanderReservoirwas morecomplicated and less distinct,
withonly2sitesdisplayingclearseasonal patterns. Flynumbersatthe 160msitepeaked
fromJanuary-April andtheflyessentiallydisappeared fromMay-December(Fig.2).At
the 300 m site, fly abundance peaked fromJanuary-May and was low orabsentduring
therestoftheyear(Fig. 3).The425 mand510msiteshadfluctuatinglownumbersfrom
February-Septemberandthe flywasabsentorbarelydetectablefromOctober-January.
Asquith: Scaptomyza anomalaas Bait Spray Monitor
73
1b
Seasonal pattern of temperature and rainfall
Alakai
3001 —p18
AvgPrecip
AvgTemp
MyJti Jl Ag%)OcNvDcJaFbMalpMyJh *0*Oc
Sampling Dole
Fig. lb.Seasonal variationin meanmonthlytemperatureandprecipitationatKanalohuluhulu,near
theAlaka'iSwamp.Kaua'i.
Table2.CorrelationsbetweenScaptomyzaannmalaabundanceandseasonalenvironmental factors
recordedatAlaka'iand4elevationsatAlexanderReservoir. Kaua'i,Hawaii.
Statistical ActualMonthly AverageMonthly AverageMonthly
Elevation(m) Parameter Precipitation Precipitation Temperature
Alaka'i
1200 F 5.590 10.180 13.800
P 0.033 0.007 0.002
r* -0.285 -0.421 0.496
Alexander
Reservoir
160 F 0.020 0.060 20.560
P 0.905 0.810 0.002
r2 0.002 0.007 0.719
300 F 3.000 3.960 5.510
P 0.122 0.082 0.047
r2 0.273 0.330 -0.408
425 F 0.500 0.510 0.170
P 0.500 0.490 0.690
r2 0.050 0.060 -0.021
510 F 1.370 0.060 0.860
P 0.270 0.810 0.380
r2 0.146 0.008 0.097
74 Proceedings ofthe Hawaiian Entomological Society Vol. 32
Alexander Reservoir
160m elevation
Ap • MyJn . Jy Ag . Sp
Sampling Date
Fig.2.SeasonalchangesinScapiomyzaanomalaabundanceatthe 160msiteatAlexanderReservoir.
Verticalbars=SE.
At theAlexander Reservoirsites, fly abundance was nevercorrelated with actual or
averagemonthly precipitation (Table2). Fly numbers atthe 160mand 300msiteswere
both negativelycorrelated with temperature, in direct contrast to theAlaka'i population.
Thisdifference isprobablypartlyattributabletoflyactivitybeinglimitedby lowtemper
aturesathighelevationsandhightemperaturesatlowerelevations,andthusthephenolo
gies atthe2sitesarcadjustedaccordingly.
ThephenologyofHawaiianinsectshasreceivedlittleattention,possiblybecausesea-
sonalily is thought to be unimportant in tropical island systems (Howarth & Ramsay
1991). However,theendemicspeciesofSciaridae,Cienosciaraftawaiiensis(Hardy),dis
plays seasonaiity at 1600 m elevation on the island of Hawaii (Slcffan 1981). In this
insect,peaknumberswereobservedduringthe wettestmonths, fromFebruary-June,and
populationsdidapparentlyrespondtospecificperiodsofhighprecipitation.Seasonalphe
nologiesfornative Hawaiian Drosophilidachavenot beenwelldocumented,butofthe2
introducedspecies examined, DmsophilasimulansSturtevantshowed strong seasonaiity
whereas D. immigrant Sturtevantdid not (Paik ct al. 1981). Given the known responses
of continental Dmsophila Fallen to seasonal fluctuations in temperature and rainfall
(Prakash&Reddy 1979,Ochando 1980,Yamamoto&Ohba 1984),evenintropicalareas
(Davidetal. 1984).thestrongseasonaiityofS.anomala intheAlaka'ishouldnotbesur-
Asquith: Scaptomyza anomalaas Bait Spray Monitor 75
Alexander Reservoir
300 • 510m elevation
o.o
CcNv . Dc . Ja . . Fb . Mr . Ap . . Myjn . JyAg . Sp
Sampling Dato
Fig.3.SeasonalchangesinScaptomyzaanomalaabundanceatthe300m.425m,and510msitesat
AlexanderReservoir. Verticalbars=SE.
prising. However, most HawaiianDmsophilacan becollected throughouttheyear,orat
least during periods of weather favorable to their activity (Bill Perreira, pers. comm.).
Dmsophila silvestris(Perkins), forexample,does not display seasonal patternsofabun
dance, but can be found throughout the yearat 1650 m on Kilauea volcano on Hawai'i
Island (Craddock & Johnson 1981), even though the mean daily temperature variation
through the year shows the same pattern and almost the exact magnitude (4 °C) as the
Alaka'i. Therefore, although the literature would suggest that the distinct seasonality of
someS. anomala populations maybeunusual among Hawaiian insects,preliminarydata
suggestthatotherlitterinhabitingarthropodsattheAlaka'i sitemayalsobeveryseason
al,sothattheextentofthisphenomenonintheHawaiianfaunashouldbeexaminedmore
closely.
TheseasonalityofS.anomalahasimportantimplicationsforbothbaitsprayprograms
andtheirenvironmental assessment.Thefactthatinsomeareas5.anomalamaybeinac
tiveorabsentasadultsduringpartoftheyearsuggestsawindowoftimethatthisspecies
maybe lessornon-susceptibletosprays.Troetschler(1983) suggestedthatseasonaltim
ingofbait sprays mightaffect nontargctspeciesdifferently,dependingontheirphenolo
gies. These data also suggest that when monitoring S. anomala for theeffects ofabait
sprayapplication,datatakenbeforeandaftertreatmentwithinthesameyearmaynotsuf
fice.Theabsenceoftheflyatthe 160mAlexanderReservoirsiteduringJuly-November,
forexample,could not beattributedtoabaitsprayappliedearlierintheyear. Rather,the
pretreatmentseasonal peakduringJanuary-April shouldbecomparedtothesameperiod
theyearfollowingtreatment.Tofurthercomplicatemonitoring,betweenyear-variationin
fly numbers was observed at theAlaka'i site. The peak May-Octobernumbers in 1991
were0.738/trap/daybut only0.551/trap/dayin 1992(f= 11.37,P<0.001).
Variationin flyphenologiesamongsitesandvariationinflyabundancebetweenyears
76 Proceedings ofthe Hawaiian Entomological Society Vol. 32
Differences in S. anomala capture
among traps at Alakai
0.8-i
1 3 6 10 2 5 9 ■
Trap Number
Fig.4.VariationinScaptomyzaanomalacaughtamongbaitedpitfalltrapsattheAlaka'isite. Traps
werenumberedsequentially,andpositionedasthreegroups(I-5,6-7,8-10),sothatnumbersreflect
trapproximitywithinagroup. Trapswithingroupswere10-15mapart.Groupswereca100mapart.
Verticalbars=SE
suggeststhat multiple, pairedtreatmentandcontrolsites would berequiredtoaccurately
assessanytreatmenteffects. Multipleyearpost-treatmentmonitoringofsites isalsosug
gestedsincetherecoveryofarthropodcommunitiesafterbaitspraysisoftencompleteand
rapid (Ehler & Kinsley 1991, Quinn et al. 1991), and the temporary suppression ofS.
anomala populations would probably not beasobjectionableas would be its permanent
extirpationfroman area.
Trapping
Variation in flynumbersamongtrapsatasitewashigh,withcoefficientsofvariation
(100(SD)/mean, Simpson et al. 1960) ranging from49.0-108.9 in theAlaka'i trapsdur
ing the peak summer months (June-September), and from 6S.7-187.2 at the various
AlexanderReservoirsites.Thisvariationamongtrapsmeansthatafairlylargenumberof
trapswouldberequiredtoaccuratelyassess the flypopulationat agiven location.Atthe
Alaka'i site, forexample, 100-200 traps would be necessary to measure the population
sizewithanaccuracyof0.05 SE(n=(s/X(,0.05))2,wheres =standarddeviationandX=
mean; Southwood 1978). However, estimating the real population size is not a require
ment foramonitoring program,and theuseofpitfall traps, particularly baitedones, isa
Asquith: Scaptomyza anomalaas Bait Spray Monitor 77
Table3. CorrelationsbetweenScaplomyzaanomalaabundanceandenvironmental factorsofindi
vidualtraplocation.
Location EnvironmentalFactor CorrelationCoefficient(r) Probability
Alaka'i Litter 0.183 >0.5
Shade -0.786 <0.0l
DirectLight 0.538 0.1 >P>0.05
Moisture ■0.048 >0.5
Alexander Litter ■0.098 >0.5
Reservoir Shade 0.319 0.1 >P>0.05
DirectLight •0.296 0.01
Moisture -0.181 >0.5
0.3
Differences in S. anomala capture
among traps at Alexander Reservoir
0.2-
o.
to
<0
0.1 -
6 9 13 2 7 8 12 20 19 15 10 18 17 14 11 4 1 5 16 3
Trap
Fig.5.VariationinScaplomyzaanomalacaughtamongbaitedpitfalltrapsattheAlexanderReservoir
site. Trapswerenumberedsequentially,andpositionedasthreegroups(1-5,6-10, 10-15, 16-20),
so that numbers reflect trap proximity within a group. Traps within a groupwere 10-20mapart.
Groupswereca0.5kmapart.
78 Proceedings ofthe Hawaiian Entomological SocietyVol. 32
relativeratherthanabsolutesamplingmethod(Southwood 1978).Theobjectiveofamon
itoringmethodforbaitsprayassessmentshouldbetoquantifyanydifferencestheremight
bein therelativenumbersofflicscaughtbeforeandafteraspray,orbetweensprayedand
unsprayed areas. Treating each sampling period as a distinct experiment increases the
sample size without increasing the number of traps installed (see Asquith & Messing
1992). This design provided sample sizes large enough to discern differences between
yearsattheAlaka'i site(seeabove)andamongsitesatAlexanderReservoir(F=6.37,P
=0.0003).Thus, 5-10traps sampled (rebaitcd) persite weekly orbiweeklyshould pro
videan adequateassessmentoftherelativenumbersofS.anomala foramonitoringpro
gram.
There were also significant differences among individual trap catches attheAlaka'i
site(F=7.5.P<0.001) with a3-folddifferencebetweenthehighestand lowestcatches
(Fig.4).Theproximityoftrapswasnotindicativeofcomparativeflynumbers.Forexam
ple, traps#2 and#3 were within 10 mofeachotheryetcatchesdifferedby 2fold. Even
greaterdifferences wereobservedatAlexanderReservoir(F= 1.89, P=0.014) whereat
the 160 m site, adjacent traps #2 and #3, also 10 m apart, differed by 5-fold (Fig. 5).
Similardifferencesinabundancebetweenandwithinsamplinglocationswasobservedfor
Drosophila plialerata breeding in fungal fruiting bodies in England (Shorrocks 1982),
though in this case, a gradientoffly density wasobservedacross the sampling location,
rather than the mosaic pattern displayed by S. anomala. Sharp changes in the
presence/absenceorabundanceoververysmalldistanceshasalsobeenobservedinother
Hawaiian Drosophila (K.Y. Kaneshiro, pers. comtn.), but in general, adult Hawaiian
Drosophilaabundanceisnotoftenquantified.
Fly abundance was not correlated with the amount ofleaf litteror soil moisture at
either site (Table 3). At theAlaka'i site, more flics were caught in traps with less shade
andsomedirectsun light,incontrasttoAlexanderReservoir, whereabundancewas pos
itively,althoughweakly,correlatedwiththeamountofshade(Table3).Iinterpretthispat
ternasreflectingtheoppositetemperatureextremesexperiencedbythefliesatthe2loca
tions.Atthe high elevationAlaka'i site, low temperaturesprobably limit fly activity, so
thateither individuals seek, or populations become larger, in warmer, sunnierspots. At
lower,drierelevations likeAlexanderReservoir,highdaytimetemperaturesandtheasso
ciatedincreaseinwaterloss potential, may makeareaswithdirectsunlesssuitabletofly
activity.
The implication of these patterns for a monitoring program is that multiple paired
traps,orgroupsoftrapsintreatmentandcontrolareas,shouldbeplacedinsimilarmicro-
habitatsto reducetheamongtrap variation in fly numbers.
CONCLUSIONS
Scaptomyzaanomalaisstronglyattractedtoproteinbait,andisubiquitousonKaua'i,
occurring in or near areas likely to receive bait spray treatments if this technique is
deemed necessary in Hawai'i. It can be easilysampledusing protein baited pitfall traps
and isadistinctive,shinyblackspeciesthatcanbeeasilyrecognizedinsamples. Inhigh
elevationforeston Kaua'i itisverysimilartoitscongenerScaptomyzahamataHardy,but
inover2yearsofsampling,thislatterspecieswas nevercollected inpitfalltraps.Atlow
elevations,S.anomalacanbeconfusedonlywithcertainsmallSphaeroccridae,butIhave
trained non-specialists to differentiate between these, so that samples can be sorted and
processed without theneedofatrainedtaxonomist.
Fiveto 10pitfalltrapssampledrepeatedlyovertimeisprobablysufficienttomeasure
relativeflyabundanceinanyparticulararea.Servicing5-10trapsrequires 15-30min.of
field work and an additional 30-60 min. ofsorting in the laboratory.Thus with a mini-