Bechinski, Edward John

Wise, K.

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Section IVBiological & Cultural ControlsBehavioral Responses of FemaleHippodamia convergens (ConvergentLady Beetle) to different colorsK. Wise and E.J. BechinskiDivision ofEntomologyUniversity ofIdahoMoscow, Idaho 83844Wise9841@uidaho.eduIntroductionOlfaction, vision andphysical contact aidboththe intermediate and shortrange-searching behavior ofbeneficial insects in locatinga stimulus (DriescheandBellows1996).HattinghandSamways (1995) demonstrated that the ladybeetleChilocorus nigritus uses a complex system ofvision and olfaction at a distance of2.5meters to locate habitat and prey. A study conducted by Obata (1986) indicated that theladybirdbeetleHarmonia axyridis uses olfactory andvisualcues to detect aphid-infestedleaves. Some research suggests that the coccinellids Coccinella septempunctata,Coleomegillamaculata and 24 other non-Hippodamia species seem to be attracted toyellow sticky traps under field conditions (Maredia et al. 1997;Udayagiri et al. 1997;Ricci 1984). Other studies showed that the capture ofH. convergens andH. parenthesisdid not differ statistically among yellow, red, black, orange, andbluesticky trapsunderfield conditions (Maredia et al. 1992 ; Capinera &Walmsley 1978). Agree et al. (1990)reported that the compound eye ofCoccinella septempunctata was most sensitive toultraviolet light at 365 nm and to green at 500 nm.An overlying question that has not been looked at in detail is this: How does H.convergens find and locateprey habitat? Thepurposeof the research reported herewas todeterminethe relative importance of colors in habitat selection byH. convergens.Specifically, I conducted experiments to determine the relative attractiveness of fourcolors (red, yellow, green and blue) to adult femaleH. convergens.MethodsAbout 5000H. convergens were collected on Moscow Mountain at anaggregation site onOctober 15, 1998. Beetles wereplaced in large paper cup containersand held in a cold storage unit at 40°F. They were fed ayeast and sugar mixture (Wheast)about once every two weeks.The beetles used for testingresponses to colorswere sexedin the coldstorageunitby examining them with a stereoscopicmicroscope. Sixty-five female beetleswereplaced in a container with an aerated lid so that air could circulate through the container.The containers with the beetles wereplacedin an environmental chamber at 30°C. Theenvironmental chamber was programmed for a photoperiod of 17hours of light and7hours of dark. This photoperiod mimics the longest day of theyear(June 21) inMoscow,Idaho. Thebeetleswere fedasmanypea aphids andwateras theycould consume forthreedays. The beetles thenwere starved for24hoursbefore testing in order to increasepotential attraction to colors.35Custom-blown Y-shaped visionometers were used to testbeetle responses tocolors. Each Y-shaped visionometer consisted of Vfc-inch diameter glass tubing in theshape of a Y. The "V" area of theY-shaped visionometer hadtwo 4-inchlong arms andthestraight entrance of theYwas 7-inch long. Thevisionometer was placedintowhitebox with an opaque divider between the two arms. A color treatment and control cardwas placed vertically at the end of each V arm. Cards were selected from a set ofColorAid artist color cards containing 220 colors. The experimental control cardwasgrayandthe treatmentswere blue, green, yellowand red. The opening at both ends ofthe arms ofthe "V"areawere covered withplastic wrap so the beetles couldescape but could still seethe treatment and control colorcards. A corklinedwithplasticwrapwas placed in thestraight entrance of theY-shaped visionometer so the insectcouldnot escape. Therewere10white boxes withvisionometers mounted horizontally on a 3 by 4-ft platform unit (5on the two longest sides of the platform.When testing the beetles, 5 visionometers wouldbe running at the same time. After each test was conducted the visionometers werecleaned in acetone to eliminate anyodors thatmay havebeen left by the previous beetles.Experiments were conducted in a white-painted walk-in controlled environmentalchamber at 35°C with 2banks ofhalide and mercury overhead lights at full intensity. Adiffusion clothwas placedoverthe top of thewhite platformholding the visionometersand the entire unit was placed on the floor in the middle of the controlled-environmentroom so there would be an even light source illuminating each card.Testing consisted ofplacing one beetle in the entrance ofeach visionometer andobserving each for 10minutes. A response was recorded when the beetle contacted theplastic wrap at the end of eitherV arm ofthe Y-shaped visionometer. If a beetle did notmove to the distant end of either V-arm after 10 minutes, I recorded the arm that thebeetle was in at the end ofthe time period.An experiment consisted ofone color treatment tested against the grey-coloredcontrol. Sample size was 100 femalebeetles (except for one ofthe green experimentswhere n was 73). Fifty beetles were tested in the morning (8:00 a.m. -10:00 a.m.) andfifty beetles in the afternoon (1:00 p.m. - 3:00 p.m.). Differences in responses wereanalyzed statistically by computing chi-square tests.Results: Beetles Responses to ColorsAll H. convergens moved to either the treatment or control arm of thevisionometer. Most of the beetles responded in the first 5 minutes. However, there were afew beetles that took most of the 10-minute time period to respond.H. convergens was not attracted to green (Figure 1). There was no significantdifference in thenumber ofbeetles ateither V-arm inboth experiments (X2exp. i=1.54, P>X2 = 0.2145, N= 73; X2exP. 2=.98, P>X2 =0.3222, N=100). When datafrom thetwoexperiments were pooled there was also no significant response (X2pooied = 0.003, P >X2= 0.9571)366050to.2 40i£ 306 20z100X2=1.54P= .2145N=73Exp. 1 Exp. 2• Green• GrayFigure 1:Responses ofH.convergens in green and gray choice test.Similarly, H. convergens was not significantly attracted to red (X2exP. i= 2.88, P>X2 =0.089, N=73; X2exP. 2=2.42, P>X2=0.1198, N=100) (Figure 2). Note that therewere alwaysmore respondents to red. However,when response data from the twoexperiments were pooled, the X2 test showed that beetles were significantly attracted tored (X2Pooied = 5.29, P>X2 0.0214, N=200).X2 = 2.88P = .0897N=100X2 = 2.42P = .1198N = 1007060 h% 50-1 40-fl> 30-jj 20 -10 -0 -• RedSGray•vrm • -' 1 'II 11IExp. 1 Exp. 2Figure2: Responses ofH. convergens in red and gray choice testFigure 3 shows thatH. convergens in experiment 1wassignificantly attracted toblue whereas in the second experiment they were not (X2exP. i= 3.92, P>X2 = 0.0477,N=73;X2exP.2=1.62,P>X2 =.2031,N= 100). Note that as with red there were morerespondents to the blue in experiment 2. However, when response data from the twoexperiments were pooled, the X2 test showed that beetles were significantly attracted toblue (X2Pooied= 5.29 , P>X2 0.0214, N=200).37X2*1.62P = .2031N=100(0©*-*oom6z70 -,P=.0477N=10060 -50 -40-30 -20 -10 -n -• BlueHGray1 1 11 11Exp. 1 Exp. 2Figure 2: Responses ofH. convergens in green and gray choice test.Figure 4 shows thatH. convergens significantly responded to gray compared toyellow inboth experiments (X2exP. i= 25.92, P>X2 =<0.001, N=73; X2exP. 2= 1.62, P>X2 =< 0.001, N= 100). When response data from the two experiments were pooled theX2 test showed there was aneven stronger response bybeetles toward gray (X2pooied =47.62 , P > X2 = < .001, N= 200).(AOO0)DO6z100806040200Exp. 1X2 = 21.78P = <001N=100Exp. 2• YellowPGrayFigure 2: Responses ofH. convergens in green and gray choice test.Discussion:Maredia et al. (1992) and Capinera &Walmsley (1978) conducted field studies onresponses ofH. convergens andH. parenthesis to red andblue stickytraps in the fieldand discovered no significant differences. In contrast, we discovered thatH. convergensmoved toward these colors under laboratory conditions. But the level of"attraction" wassubtle and depended on using large (n = 200) numbers ofH. convergens. Only whendata from the 2 red experiments were pooled could we detect a strong statisticallysignificant attraction by the beetles. Likewise, only when data from the 2 blue38experiments werepooledcouldwe detect a strong statistically significant attraction bythe beetles.Maredia et al. (1997), Udayagiri et al. (1997) and Ricci (1984) stated that 26 non-Hippodamia coccinellid species seemed to be attracted to yellowsticky traps under fieldconditions. In contrast, our lab studies showedthatH. convergens seemedto be highlydeterred by yellow and so suggestthat yellow is a poor choice forH. convergens traps.However, we need to determine ifH. convergens is really deterredby the yellowhue or ifinstead beetle response is due to the intensity of the reflected light from the yellowcard.We also need to test yellow in pair-wise comparisons with other colors to determine thepotential role of contrast in beetle responses.References:Agree, H. R., Mitchell, E. R. and Flanders, R. V. 1990.Spectral Sensitivityof theCompoundEye ofCoccinella sepetempunctata (Coleoptera: Coccinellidae).Annals oftheEntomologicalSocietyofAmerica. 83 (2) 817-819Capinera, J. L. and Walmsley,M. R. 1978.VisualResponses of SomeSugarbeet Insectsto StickyTraps andWater Pan Traps ofVarious Colors. Entomological Society ofAmerica. 926-927Hattingh, V. and Samways,M. J. 1995.Visual and Olfactory Location ofBiotopes, PreyPatches and Individual Prey by the LadybeetleChilocorus nigritus. EntomologiaExperimentalis et Applicata. 75: 85-98Maredia, K. M., Gage, S. H., Landis.D. A. andWirth, T.M. 1992. VisualResponse ofCoccinella septempunctata (L.)Hippodamiaparenthesis (Say) (Coleoptera:Coccinellidae) and Chrysoperla cornea (Stephens), Neuroptera: Chrysopidae) toColors. Biological Control 2: 253-256Udayagiri, S.,Manson, C. E., and Pesek, J. D. 1997. Coleomegilla maculata, Coccinellasepetempunctata (Coleoptera: Coccinellidae), Chrysoperla carnea (Neuroptera:Chrysopidae), andMacrocentrus grandii (Hymenoptera: Braconidae) Trapped onColored Sticky Traps in Corn Habitat. Biological Control. 26: (4) 983-988Ricci, C. 1984. BeneficalCoccinellidae in Yellow Traps in SomeItalian Regions.Ecology ofAphidophaga. Dr. W. Junk Publishers, p. 441-44739

Behavioral Responses of Female Hippodamia convergens (Convergent Lady Beetle) to Different Colors

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Behavioral Responses of Female Hippodamia convergens (Convergent Lady Beetle) to Different Colors

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