Macrolepidopterous moths : collected by blacklight trap at Cooper's Rock State Forest, West Virginia : a baseline study

32 Pages·1991·1.4 MB·English

by  Butler, Linda, 1943-

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Authors
LindaButlerisProfessorofEntomologyandVickiKondoisEntomology
ResearchAssistant,DivisionofPlant andSoilSciences, Collegeof
Agriculture andForestry,WestVir^niaUniversity.
USDA
Thisresearchwassupportedinpartbyagrantfromthe Forest
Service andinpartfromfundsoftheWestVirgmiaAgricultiu-aland
ForestryExperimentStation.Wewouldliketoacknowledgethe
assistanceofDr. EdwinTownsendindatamanagement.
WestVirginiaUniversity
AgriculturalandForestryExperimentStation
College ofAgriculture andForestry
RobertH.Maxwell, Director
Morgantown
Macrolepidopterous Moths
Collected by Blacklight Trap
at Cooper's Rock State Forest,
West
Virginia:
A
Baseline Study
Linda Butler and Vicki Kondo
Introduction
Lepidoptera, particularlyMacrolepidoptera, have been the subject of
considerable interest in recent years as indicators ofbio-diversity and en-
A
vironmentalbalance. numberofMacrolepidoptera(primarilybutterflies)
are considered endangered or threatened, especially because of habitat
destruction.
As the gypsymoth {Lymantria disparL., Lymantriidae) moves into the
central and southern Appalachians, concern grows for the possible impact
ofgypsymothdefoliationandsuppressionprogramsonnon-targetLepidop-
tera. To determine such impacts, baseline data collected by appropriate
samplingmethods are essential.
Various types ofUght traps have long been usedfor control, survey or
We
ecological studies of Macrolepidoptera. report here the results of a
three-year study ofmacrolepidopterous moths found at theWest Virginia
University Forest at Cooper's Rock State Forest, conducted to estabHsh
baseline data prior tobuild-up ofgypsymoth populations. We also discuss
use ofblacklighttrappingforbaseline andnon-targetimpact studies.
Literature Review
Asearlyas1879,lighttrapswerebeingusedtocollectinsects(Comstock
1879).WiEiams(1939)listedthreeobjectivesintheuseofhghttraps: (1) the
collectionofinsectspecimenstostudydistributionortaxonomy;(2)thestudy
of insect ecology by evaluating numbers of captured specimens active at
particular locahties or dates and changes in populations due to climatic
variation; and (3) a means of control for certain insects. Wilhams (1939)
referredtonumerousreports oflighttrapsusedforthesepurposes.
An excellent summary oflight-trap studies was presented by Hienton
(1974),withareviewoftrapdesignchangesovertheyears.Designstandards
forblacklighttrapsforinsectsurveysweregivenbyHardingetal.(1966)and
Smith et al. (1974). Light traps of many types have been compared for
efficiency in capturing moths. Cantelo (1990) compared blackUght and
Robinsonmercuryvapor traps for catch ofagricultural pests. Frost (1957)
comparedinsectcapturestakenwiththe PennsylvaniaUght trapwithtraps
ofotherdesigns.OthercomparativestudieshavebeenreportedbyBrether-
ton(1954), Vaishampayan andVerma (1983),Williamset al. (1955), Smith
et al. (1959), Labanowski (1980), Warmg (1980), Heath (1966) and Belton
andKempster (1963).
Lighttrapsfittedwithpolarizingfilterswere more attractiveto certain
mothsthantrapswithoutfilters(Davidsonetal.1973).Light-trapcollections
ofeconomicallyimportantmothsincreasedwhenlighttrapswerebaitedwith
phenylacetaldehyde (Cantelo andJacobson 1979). Novak (1983) described
amercuryvaporlighttrapincorporatinganelectrifiedwiregridforsampling
A
moths of agricultural importance. Texas-type trap equipped with
electrodeswas found to increase catchnumbers and speciesnumbers over
trapswithout electrodes (Mizutani et al. 1982). Hollingsworth et al. (1961)
showed that light-trap catches could be altered by enclosing traps with
cylinders of hardware cloth of different mesh sizes. They also found that
artificialwindbreakstoshieldtrapsfromeffectsofprevailingwindincreased
trap catches. Ammar (1975) increased efficiencyofUght traps for catching
small Lepidoptera £md other insects by using wire mesh. Robinson and
Robinson(1950) discussedthebehaviorofmothsnearlighttrapsofvarious
A
designs. recent discussion oflight-trap designs and their relationship to
captureefficiencywasgivenbyMuirhead-Thomson (1991).
Lighttrapshavebeenevaluatedascontrolagentsforvariousagricultural
pests, pzirticularly tomato euid tobacco hornworm, European corn borer,
A
cabbage looper, corn earworm andpinkboUworm. reviewofthe subject
wasgivenbyCantelo(1974) ResultsofUghttrappingforcontrolofeconomi-
.
callyimportantspecieshavebeenmixed.Inathree-and-one-halfyearstudy
ofmasstrappingofmothsisolatedonSt.Croix,U.S.VirginIslands,Cantelo
etal.(1974)notedthatpopulationsofseveralpestspeciesofSphingidaeand
Noctuidaedeclined.WilUams (1939), however, notednoconsistent decline
in 150speciesofNoctuidaeand Geometridae,manyofwhichwereagricul-
tural pests, that he coUected in four years at Rothamsted, U.K. In further
coUectionsatthesamelocationoveranine-yearperiod,Tayloretal. (1978)
recordedwidefluctuations,butnodownwardtrendsinspeciesnumbers.
SomearrangementsordensitiesofUghttrapsmightincreasepestnum-
berswithin an area. Debolt et al. (1979) statedthatup to 14times asmany
cabbageloopereggswerefoundinUghtlytrappedasinheavilytrappedareas.
Smith (1962) noted that a Ught trap at one locationinWisconsin appeared
tostimulate anoutbreakofannywonnbyattractingmothsintothe area.
Extensive Uterature reports the use of light traps in survey of moths,
particularlythose ofagricultiiralimportance. Attempts havebeen madeto
use data to predict pest outbreaks, to forecast population trends, to time
pesticide apphcations and to monitor effectiveness of controls. Light-trap
surveys throughout the world have been instrumental in detecting new
regionalandnationalrecordsfromimmigrantspecies ofmoths.
Light traps are valuable in many types of ecological and bionomical
studies including flight phenology, migration patterns, long-distance flight
capability, nocturnal flight time, sex ratios, voltinism, winter survival,
reproductive potential and mating status. Morphological studies such as
determination ofmelanism and insect wing lengthvariations use Hght-trap
collections.
Theinfluence ofweather onlight-trap catches hasbeenthe subject of
manystudies; impact ofmoonphase, temperature, humidity, rainfall, wind
and barometric pressure have been discussed. Light-trap captures are
generally higher on warm, humid nights with no moonHght (McGeachie
1989).
Amothmayreachalighttrapbyeitherchanceorattraction;thedistance
overwhichattractionoperatesishighlydependentonlightintensityandlight
wavelength (Hartstack 1979). Most researchers agree that the distance of
positive attraction is no more than a few hundred feet. Obviously, this
distanceisalsodependent onsexandspecies ofmoth, amongotherfactors.
Somespeciesmaydispersemorewidelyduringsomeyears (asdiscussedby
Sargent, 1976, for Catocala duringperiods ofgreat abundance), andhence
by chance may come within attraction distance of hght traps. Baker and
Sadovy (1978) used mark-release/recapture methods for estimating the
distance ofresponse ofmoths to a 125-watt mercuryvaporUght trap. They
concludedthattheresponserangeofthetwomothspeciesstudiedwas only
about three meters. In tests with 15-watt blacklight traps, Manduca sexta
m
(Johannson) (Sphingidae) exhibitedattractionwithin4.6 oftheradiation
source, and forHeliothiszea (Boddie) (Noctuidae) the distance was 6.1m
(Stewartetal.1969).Incontrast,SpodopteralittoralisBoisduval(Noctuidae)
m
was attractedto a6-wattblacklightfromatleast200 (Plaut 1971).
WiUiams(1940)usedhght-trapcatchesofinsectsasatoolforestimating
andforecastingchangesininsectpopulations.Hestatedthatitisp)ossibleto
correct meaninsect catchfor eachmonthfor itsvariationfrom the normal
duetochangesintemperature,wind, andotherfactors.Theresultwouldbe
avalueforwhatthecatchwouldhavebeenifallconditionshadbeennormal
forthe month. Thedifferences thatremain, according toWiUiams, are due
to population effects. King and Hind (1960) presented a method for the
calculationofthetheoreticalcatchlevelofinsectstakeninUghttraps.They
suggestedthatdeparturesfromthetheoreticalcatchare duetohighor low
activityandmustbeaccountedforbyweather.Williams(1940)discussedthe
concept that short-term (daily) variations in insect catch are functions of
activity rather than population changes, and that long-term (seasonal or
annual)variationsincatcharefunctionsofchangingpopulationratherthan
ofactivity.
Lighttrappingisarelative,notabsolute, methodofpopulationestima-
tion (Southwood 1978). In criticizing the use oflight traps for population
estimation, Taylor and Carter (1961) stated thatthenumber ofanyspecies
caughtdependsnotonlyontheircommonnessbutalsoontheirattractedness
to light. Taylor and French (1974) noted further that the relationbetween
thecatchandtheparentpopulationisnotknown,hencethecatchcannotbe
treatedasatruesample.Theystressedtheimportanceofselectingsampling
sitesasalikeaspossibleifcatchesfromdifferenttrapsaretobecompared.
Taylor and Brown (1972) noted that a light-trap catch represents a
congregationatapointinspace.Theydistinguishedthreedifferentfunctions
relating catch and space that may help to envisage the catch as a sample.
They distinguished between local and migrant activity and discussed the
concept of "area of influence" of the trap. White (1989) noted that the
trappableareaitselfisrarelydefinable.Hartstacketal. (1968) usedaseries
ofoil-and-water-filledpansdisplayedciroundlighttrapstomeasureefficien-
cyoftraps. Theyconcludedthat large numbers ofinsects attracted to Ught
traps are not caught. McGeachie (1988) used a video camera to estimate
light-trap efficiency in the field. He divided insect flight tracks into three
categories: (1) newarrivals, (2) passers by and (3) local flights. While trap
efficiencyvariedwithwindspeed,herecordedamaximumof39%efficiency
invirtuallycalmconditions.
Sargent (1976) notedthattherelative abundance ofa speciesmayvary
considerably from year to year at a given location; the overall pattern of
speciesabundancealsovariesovertheyears.Sargent'scommentsweremade
psirticularlyregardingrecordsofSA.HesselwholighttrappedCatocalaspp.
(Noctuidae)onvirtuallyeverynightoftwelveconsecutiveCatocala seasons.
The variation in Hessel's data ledSargent to suggest the futilityofmaking
long-termassessmentsofpopulationsbasedonrecordsfromasingleseason
at any locality no matter how extensive collecting may be that season.
RejmanekandSpitzer (1982) reportedresults ofa 12-yearstudyoffluctua-
tion in populations of noctuid moths in Bohemia. They discussed the
relationship between species diversity and species stabilityin Lepidoptera
communitiesmonitoredbylighttrapping.
SpitzerandLeps (1988) studiedyear-to-yearvariationinabundanceof
noctuid mothsinthree Central European habitats differingin successional
status and degree of disturbance. Highest variation was found in moth
species with a high population growth rate. Climax habitats supported
populations ofmoths with lowvariation in abundance and lowpopulation
growthrate.
White(1989)discussedtheconceptof"dilutionratios"ofmothsastheir
numbers are reduced due to frequent trapping. Thomas (1989) noted that
the optimum frequencyfor Ught trapping at a given sitewas everythird to
seventh night. He stated that with care, Ught trapping and live release can
provide valid population indices for comparison between generations and
yearsforagivenmothspecies.
Placement of light traps greatly influences moth catch. Hausmann
m
(1990a) found that two light traps located only 45 apart showed great
differencesinspeciescomposition.Henotedthatthemethodofusingsingle
light traps has to be regzirded as site specific and must be considered in
ecological interpretations ofdata. Williams et al. (1955) discussed the im-
portance of rotating traps among designated trapping sites to minimize
effectsofdifferencesamongtraps.
In a study comparing light-trap catches in deciduous and coniferous
woodlandhabitats, Waring (1989) warnedthatwoodland studies are espe-
ciallychallenging because ofthe amount ofshading and screening ofUght
traps byvegetation. He stressed the need for carefully choosing Ught-trap
sites. Magurran (1985) studied differences in Macrolepidoptera in Ireland
andnotedthatinsectdiversitycanbecorrelatedwithsitefactors,butasthe
relationshipis averycomplexone, suchcorrelationsshouldbeinterpreted
withgreatcare.
Mizutani (1982) arranged 10Ughttraps in aUne at regularintervals of
28.6 m between two forests about 200 m apart. He found that catches of
mothswere greatestin numbers ofspecies andindividualswithin about 30
mfromtheforestedgeand concludedthat30mfromtheforestedgeisthe
mostsuitableplacementforaUghttrap.
A number ofstudies have been conducted on the use ofUght traps to
evaluatethe Macrolepidoptera community at a single site over a period of
severalyears. Dirks (1937) recorded344 species ofMacrolepidopteracol-
lectedoverafour-yearperiodatonesiteinOrono,Maine.Duringhisstudies
atRothamsted, WilUams (1939) coUected356 species over fouryears. The
Rothamstedinsect survey, which includes moth monitoring, has continued
A
smce 1969. history ofthe surveywas given byTaylor (1979). During six
yearsofblackUght-trapcoUectionsatArchboldBiologicalStationinFlorida,
Frost (1964) captured330Macrolepidopteraspecies. Inarecentstudyofa
New Jersey oak forest. Moulding and Madenjian (1979) recorded 410
speciesoverafive-yearperiod.
Rings et al. (1987) conducted a nine-year study ofthe Lepidoptera of
the Wilderness Center, Stark County, Ohio, and recorded 426 species of
macrolepidopterous moths. In similar studies at Atwood Lake Park,
MohicanStateForest andState Park andFowlerWoods, Ohio, Rings and
Metzler (1988, 1989, 1990) listed 382, 417 and 374 forms and species of
macrolepidopterous moths, respectively. Sampling methods for these
studies included ultraviolet light traps, mercury vapor light, bait traps,
sugaringandnetting.
Holloway(1984) advocatedtheuseoflight-trapsamplingofmothsasa
means of indicating response of rain forest insect communities to distur-
bance.Heconcludedthat thissimple and quickapproachuseselementsof
thefaunathatareeasilysampled,widelydistributed,diverse,showspecificity
tovegetationtype, andaresensitivetochange.
RecentandongoingstudiesarebeingconductedintheeasternUnited
StatesusingUghttrappingtoestablishbaselinedataandtoevaluateimpact
ofgypsy-mothdefohationorspraysappliedasapartofgypsy-mothsuppres-
sion programs. Peacock and BuUington (1989) recentlyconducted a study
oneffects oiBacillusthuringiensisBerlinerwar.kurstakionnativeLepidop-
tera in the Shenandoah National Park, Virginia, using blacklight traps to
monitormothpopulations.Theynotedthattotalseasoncaptureofselected
species in treated and untreated areas was extremelyvariable, prohibiting
anylegitimateanalysisofthedata.
Sample (1991) recentlycompleted astudyofdiflubenzuron impact on
non-target insects as food of the Virginia big-eared bat in West Virginia.
Blacklighttrapsoperatedinsevenpjiirsoftreatedanduntreatedplotswere
the primary sampling tools. Sample found that total species richness and
species richness in four ofeight Lepidoptera famiUeswas reduced. Ofthe
83 macrolepidopterous species in sufficient abundance for statistical
analysis,47weresignificantlyreduced.
In an ongoing study in the Great Smoky Mountains National Park,
Watson and Lzunbdin (1989) are collecting baseline data on Lepidoptera
priortobuildupofgypsy-mothpopulations.Blacklighttrapsarebeingused
tocollectsamplesfrom 10permanentsites,fiveeachinNorthCarohnaand
Tennessee.
Light trapping ofinsects has provided valuable information on insect
distribution, taxonomy, ecology, and control for more than a century. Cur-
rently,light traps areparticularlyusefultoolsfor establishingbaselinedata
andformeasuringimpactsduetoforest disturbancebypesticidespraying.
Materials and Methods
This study was conducted at the West Virginia University Forest at
Cooper's Rock State Forest, located in Preston and Monongalia counties
about32kmeast ofMorgantown,WestVirginia.The areaconsistsofa50-
to60-yearoldeven-agedmixedmesophyticforestandhasameanelevation
m
of561 (Carvell1983).NeartheUghttrappingsitethecanopyiswhiteand
red oak {Querus alba L, Q. rubra L., Fagaceae) and the understory is red