wAÌ'l'þ. lì\'';ll lll'['E zo' r D't5\ Liiliì,¡'ï17 BEHA\TIOIIR 0F EIRST INSTÁR EeIrcPß EXC{IRSARIA(I.BPII}OPIERA: GEOITETRIDAE) IN RELATTON TO HOST-ETNDING PROCESS by RAMÅN RÄ}ÍACIÂ}IDRÂN B. Sc. (Âg), M. Sc. (I.À.R.I.' NBIü DEIflI). A thesLs subnítted for the degræ of Doctor of PhiTosophy 7n the FacuTty of AgricuTturaT Scienæ to the Aníversity of AdeLaide. /. 1'¡¡..... '-- ?5'" Jvt,--t , /-{'-ì8å Department of Entomology, I{aite .Agrlcultural Research Institute, Ttre Unversity of Adelaide. MARCI, 1986. PLATE 1 First lnstars of Ectropis excursaria on the edge of a citrus leaf. IO MY PÂRENÏS TABT,E OF CONTENIS SIIMMÄRY t DECLARATIOII iv ACKiIOWI.EDGH,IM{TS v CfrAPTER 1 I}ITRODUGIIOI{ I ffiAPTER 2 PRBLII{INÂRIËS 2,I General Methods. 5 2.2 Hatchíng of eggs. 6 2,2.t Hatching in the field. 7 2.3.I Hatching in laborat,ory. 7 CTAPTER 3 \TISUAL BBHAVIOIIR OF HTRST INSTAR ECIROPIS EXCTIRSARIA 3.1 fntroduction. 10 3.1.1 Role of vision in detection of host plants. 10 3.I.2 Role of vision in the host-finding of larval stages of lepidoptera. 11 3.2 Response of first. instar caterpillars to vertical and horizontal angles subtended by objects. 11 3.2.L Materials and methods. L2 3.2.2 Results and discussion t3 3.3 Discrimination of objects on the basis of vertical and horÍzontal angles. L4 3.3.1 Matería1s and methods. T4 3.3.2 Results and discussion. 16 3.4 Distance perception in caterpillars. T7 3.4.I Materials and methods. L7 3.4.2 Results and discussion. o.;.44a*lon 20 3.5 Role of visual and chemical cues in the set+++ng behavlour of caterpillars. 25 3.5.1 Materi.als and methods. 25 3.5.2 Results and discussion. 26 CfrAPTER 4 GK}TACTTC AND PHO]ÛTASTIC BffiAVIOUR OF FITROPIS EXCURSARTA 4.1 Introduction. 29 4.1.1 Upward migration of caterplllars. 29 4.I.2 Gravit.y. 29 4.L.3 Response to gravitY. 30 4.I.4 Geotaxis in insects. 30 4.2 Geotaxis in caterpíl1ars. 32 4.2.L The role of light and gravity ín the behaviour of caterpillars. 33 4.2.2 Angle of inclination of walking surface and its influence on response to gravity. 34 4"2.3 Influence of the curvature of walking surface on response to gravity. 38 4.2.4 Behaviour on a flat inclined surface. 39 4.2.5 Response in a centrifugal field. 42 4.2.6 Interaction of light and gravíEy in the behaviour of first instars. 47 4.3 Effect of food deprivation on response to light and gravlty of the first instars. 52 4.4 Geotactlc behaviour 1n caterpillars of later instars. 54 4.5 Response to light and gravit.y in pre-pupa1 stage. 55 4.6 Process of gravity perception in insects. 58 4.7 A club form sensory hair in the first insLars. 62 4.7.t Introduction. 62 4.7.2 Morphology. 63 4.7.3 DistrÍbution of the hair. 63 4.7.4 Distríbution with respect to the instar of the caterpillars. 64 4.7.5 Orientation of the sensory halr. 64 4.7.6 Geometrical parameters of the hair. 64 4.7.7 Role of the sensory hair in the behaviour of caterpillars. 65 4.7.8 Discussion. 69 IÙIND DISPETTSAL OF ETRST INSTAR BSIROPTS EXGIIRSARTA I Behaviour of caterpillars on vertical objects. 72 5.1.1 Effect of temperature on time spent on vertical objects. 73 5.I.2 Effect of releasÍng the insect on the top or the bottorn of a vertical object on Lhe rrcharacteristic stance behaviourrr. 75 5.1.3 Effect of temperature on the time spent one posltion. 76 5 .I.4 Effect of the height of the object on time spent on a verLical object. 77 5 .1.5 Movement of the caterplllars with respect to tíme of the day. 78 5 .1.6 Time on an object: Time from hatching or time S penL on Lhe object . 79 5 .L.7 Effect of tlme on the length of downward j ourney. 80 5 .1.8 Downr'¡ard excursions-Response to stimuli . 80 5 .1.9 Discussion. 81 5.2 hlind dispersal of first instars. 85 5.2.L Introductíon. 85 5.2.2 l,lind dispersal. 86 5.3 Effect of host plants in wind dispersal of first lnstars. 8B 5.3.1 Materials and met,hods. 88 5.3.1.1 Experinent I, 89 5.3.1.2 Experíment 2. 90 5.3.1.3 Experiment,3. 90 5.3.1.4 Experiment 4. 90 5.3.2 Results. 9L 5.3.2.1 Experirnent 1 . 91 5.3.2.2 Experiment 2. 91 5.3.2.3 Bxperiment 3. 9t 5.3.2.4 Experiment, 4. 91 5.3.3 Discussion. 93 5.4 Ternlnal velocity of fírst. instars. 99 5.4.L fnLroductlon. 99 5.4.2 Materials and rnethods. 100 5.4.2.1 Experi.ment 1. 101 5.4.2.2 Experíment 2. 101 5.4.2.3 Experiment.3. 101 5.4.3 ResulEs and di.scussion. to2 5.4.3.1 Termlnal veloclty of the first insLars. 102 5.4.3.2 Effect of silk J-ength and size of the insect on terminal velocÍty. 104 5.4.3.3 Effect of aerial maneouvring of fÍrst insLars on terminal velocity. 105 CflAPIER 6 STIR\ITVAL PO|IENrIAL OF F"IRST TNSTAR EGIROPIS ETCTJRSARIA 6.1 ïntroduction. 107 6.2 Effect of temperature on the duration of survival of first instars. 109 6.2.L MaLerÍals and methods. 109 6.2.2 Results. 110 6.3 Effect of temperature and humidiLy on the duratlon of survlval of first instars. 110 6.3.1 Introduction. 110 6.3.2 Materials and methods. 110 6.3.3 Results and discussion. 111 6.4 Effect of food plants on the survival of first instars. 114 6.4.I Introduction. 6.4.2 Materials and nethods. 114 6.4.3 Results and discussion. 115 6.4.3.1 Effect of food plants on the survival of first instars. 116 6.4.3.2 Effect of food plants on the growth of caterpillars. 119 6.4.3.3 Effect of food plants on the pupal welght of caterpillars. r20 6.5 Effect of selective rearing on the performance of progenies. L2T 6.5.1 Materials and nethods. L22 6.5.2 Results and discussion" 123 6.6 Effect of food deprivation on the establishnent of flrst instars on host plants. L25 6.6.1 Materials and ¡nethods. L2s 6.6.2 Result and discussion. L2s 6.6.2.1 Effect of food deprivation of the survival of first instars. L25 6.6.2.2 Effect of food deprivation on the duratÍon of first sLadium. 126 CHÄP1ER 7 GENERAT DISCUSSION L29 7.L Host-finding process of the first lnstar Ectropis excursaria. L29 BIBLIOGR.APET APPENDICBS LIST OF TABIJS ÁND IIUEIR LoCATION llf lfE lEft l{o. Title After page 2.L Hatching pattern in the field. 6 3.1 Three-way ANOVA of the counts of newly emerged and fasted first instar caterpillars at differenL places in the experimental area. 26 3 .2 DistribuLion of caterpillars at different places at different observational periods. 26 4.L Distribution of insects in the canister. 33 4.2 lrratson-hlilliamrs tesl to compare the mean direction of Ínsects in experiments conducted on two different days. 45 4.3 Centrifugal accelaratÍon and the circular statistical parameters for the distribution of the first ínstars in petridish size f. 4s 4.4 Centrifugal acceleration and the circular statistical parameters for the distribution of the first instars in petridish size II. 45 4.5 Effect of food deprivation on geotactÍc behaviour. 53 4.6 Effect of food deprivation on phototactic behaviour. 53 - 4.7 Effect of food deprivation on the rate of movement of the first instars. 53 4.8 Comparison of the reaction of the first and fifth instar caterpillars Lo centrifugal acceleration. s4 4.9 l,ilatson-l{il1iamts test for comparison of the mean directions of the first and fifth ínstars in centrifugal fie1d. 5l+ 4.10 Behaviour of pre-pupa in a centrifugal fie1d. 56 4.11 Angular parameters of the walking behaviour of insects after immobilization of some organs. 61 4.Ii Frequency of sensory hairs in the dífferent part.s of the caterpillars body. 63 4.13 Geor¡etrical parameters of the hair. 64 4.14 Maximum possible deflection in the sensory hair of different orientations. 66 4.15 Effect of gravity on the deflection of the sensory hair. 66 5.1 Tíme spent on a vertical object at dífferent temperatures. 74 5.2 Effect of releaslng the insect at the top or bottom of a vertlcal object on the trcharacteristic stance behaviourrr 74 5.3 BehavÍour on a vertical object: Counts of Ínsect movement. 76 5.4 Estlmated probablllties of movlng at various temperatures. 76 5.5 Effect of ternperature on the tirne spent in a single characteristic stance. 74 5.6 Effect of light and darkness on the numbers moving away fron the object (temperature experimeot). 78 5.7 Effect of light and darkness on the nunbers noving away fron the objecÈ (height. experiment,). 78 5.8 Frequency distributlon of the distance moved down by Ínsects at various time intervals. 78 5.9 Effect of host plants on the dispersal of first instars. 91 5.10 Multiple comparison of iaecal pellet production at different tines after incubation with host foliage.