52 David Logan and Christina Rowe

Site selection and time of eclosion on kiwifruit vines by final-instar nymphs of the chorus (: ) David Logan1 and Christina Rowe2 1The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland Mail Centre, Auckland, 1142, New Zealand. 2The New Zealand Institute for Plant & Food Research Limited, 412 No 1 Road, RD2, Te Puke, 3182, New Zealand. Email: [email protected] Abstract We studied the site and time of eclosion on kiwifruit vine trunks for final-instar nymphs of chorus cicada, Amphipsalta zelandica (Hemiptera: Cicadidae). Final-instar nymphs selected sites with a median angle of 72o above horizontal. There was less discrimination for the height of eclosion site (median 0.93m). Most eclosion was observed 1.5h-2.75h (10pm-11.15pm) after sunset. Some nymphs continued to emerge and eclose up to7.3h after sunset (3.40am).

Introduction Chorus cicada, Amphipsalta zelandica (Hemiptera: Cicadidae) is an endemic and widespread species that has successfully colonised kiwifruit orchards (Logan & Connolly 2005). are well known because of their summer song and the exuviae of final-instar nymphs left on tree trunks and other upright structures. Emergence of final-instar nymphs from the soil typically occurs at night for overseas species (Moulds 1990; Williams et al. 1993), and this may also be the general case for New Zealand species. One of us (CR) observed that A. zelandica exuviae tended to be aggregated on sections of kiwifruit vine and tree trunks that made an acute angle with the soil surface. Here we estimated the time of the day when final-instar nymphs of A. zelandica moult to adults and characterised

The Weta 47:52-57 53 eclosion sites by height and angle above horizontal to test whether there was site discrimination. Methods Height and angle from horizontal were measured for 262 A. zelandica exuviae on trunks of Hayward kiwifruit vines in an orchard block at the Te Puke Research Orchard of Plant and Food Research. Measurements were during 29 January – 3 February 2014. A camera and flash were established to focus on the base of a vine in a block of Hayward kiwifruit. The camera and flash were powered by running 12v DC from a battery through an inverter. The time- lapse sequence was initiated about 8:30 pm and images were taken every 30s until the following 8.00 am. The procedure was repeated for three nights in early February 2012 and one night in late January 2014. Eclosion was not observed for most cicadas as it occurred outside the camera’s field of view. Instead we used the time that nymphs began ascending the vine trunk as an approximate measure for the time of eclosion. Results and Discussion Site selection by final instar nymphs for moulting on kiwifruit vines does not appear to be random. The median angle at which eclosion occurred on vine trunks was 72o above horizontal with most nymphs (82%) moulting between 50o and 80o (Fig. 1). The distribution of angles suggests that final-instar nymphs select sites that make an acute angle with the soil surface. This behaviour may enable the new imago to use gravity to assist in the process of leaving the exuviae. Some exuviae also occur above the vine trunk and were not measured. They tended to be found underneath leaves and on lower sides of vine leaders and canes consistent with our observation that moulting sites are inclined at <90o from the horizontal. However further observations on other plant species are warranted to generalise our conclusion. Median height of exuviae was 0.93m (n=262) with heights above 0.4m preferred (Fig. 2). The height of [Type text]

54 David Logan and Christina Rowe the vine trunk set an upper limit of ca. 2.0m to observations. In forest we have observed a few A. zelandica exuviae at ca. 3m and it is possible some nymphs moult higher.

Figure 1. Angle from the horizontal of eclosion sites for A.zelandica exuviae on kiwifruit vine trunks.

Figure 2. Distribution of the heights of A. zelandica exuviae on kiwifruit vine trunks.

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Eclosion by chorus cicada nymphs (n=27) occurred throughout the night (Fig. 3). The earliest cicada nymph was observed approximately 1.5h after sunset (9.57pm) and the latest approximately 7.3h after sunset (3.40am). Most of the nymphs (15/27) were recorded reaching the vine base between 10.01 and 11.16pm. Eclosion was observed for one individual and took 50 mins. Time-lapse flash photography proved useful to study the general phenology of cicada nymph movement prior to eclosion (Fig. 4). It also revealed a hedgehog removing an imago completing its moult near the soil surface (Figure 5).

Figure 3. Distribution of eclosion times for A. zelandica on a kiwifruit vine. Times are the combined observations of three nights in early February 2012 and one night in late January 2014.

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56 David Logan and Christina Rowe

Figure 4. Paths taken by A. zelandica nymphs prior to eclosion on a kiwifruit vine. This image is a stack of consecutive images taken every 30s with the paths of individual cicadas as separate coloured lines.

Figure 5. Hedgehog observed with a new A. zelandica imago (indicated by arrow). Both hedgehog and cicada were missing in the next image taken 30s later.

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Acknowledgements Tim Holmes and Sam Ong provided assistance with the camera setup.

References Logan DP, Connolly P. 2005. Cicadas from kiwifruit orchards in New Zealand and identification of their final instar exuviae (Cicadidae: Homoptera). New Zealand Entomologist 28:37-48.

Moulds M. 1990. Australian cicadas. New South Wales University Press, Kensington. 217 pp.

Williams KS, Smith KG, Stephen FM. 1993. Emergence of 13-Yr Periodical Cicadas (Cicadidae, Magicicada) - Phenology, Mortality, and Predator Satiation. Ecology 74(4): 1143-1152.

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