Nocturnal Flight Activities of the Female Asian Gypsy Moth, Lymantria Dispar (Linnaeus)(Lepidoptera: Lymantriidae)
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Appl. Entomol. Zool. 45 (1): 121–128 (2010) http://odokon.org/ Nocturnal flight activities of the female Asian gypsy moth, Lymantria dispar (Linnaeus) (Lepidoptera: Lymantriidae) Ren IWAIZUMI,1,* Kenryo ARAKAWA1 and Chiharu KOSHIO2 1 Research Division of the Yokohama Plant Protection Station; Yokohama, Kanagawa 231–0801, Japan 2 Naruto University of Education; Naruto, Tokushima 772–8502, Japan (Received 5 November 2008; Accepted 17 August 2009) Abstract The flight and other behavior of the female Asian gypsy moth, Lymantria dispar, were observed in a net cage under natural photoperiodic conditions in May–August in Yokohama City, Japan. Both virgin and mated females moved by flight between 19:00 and 21:00, which coincided with one to two hours after sunset. Virgin females continued releas- ing pheromone, i.e., calling behavior, at the new site and sometimes copulated with males at night. If they could not copulate that night and in the subsequent daytime, they flew again the subsequent evening. Mated females started oviposition after their flight and thereafter did not move again. The mean flight speed of a virgin female was estimated as 21.3 m/min. The flight duration was approximately 10 min for both virgin and mated females, and therefore females could move 200 m on average and a maximum of 750 m during one night. These nocturnal activities of the Asian gypsy moth should be considered in order to establish effective control. Key words: Asian gypsy moth; flight activity; Lymantria dispar; mating behavior; reproduction Asia (China, Korea, Far East Russia etc.). In Japan, INTRODUCTION L. dispar japonica is distributed in Honshu, The gypsy moth, Lymantria dispar (Linnaeus), Shikoku, Kyushu and southwestern Hokkaido, and is distributed widely in temperate regions and at- L. umbrosa is distributed in Hokkaido. Studies to tacks a very wide variety of trees; thus, it is the clarify the taxonomic status of each AGM are un- most notorious pest of forests and ornamental trees derway. in the world (Leonard, 1974). It is classified into Recently, the U.S. and Canadian governments two groups (types), the European gypsy moth have become very anxious about the invasion of (EGM) and Asian gypsy moth (AGM), and the bio- AGM into their territories (Myers et al., 2000), and logical differences between the two groups, e.g., have requested that countries with AGM control host range, female behavior, as well as genetic dif- them in port export areas, and to certify that ships ferences examined by DNA analysis, were reported destined for the United States and Canada are free (Bogdanowicz et al., 1993, 1997; Pfeifer et al., from AGM egg masses (Yokochi, 2007). Thus, 1995; Schreiber et al., 1997; Reineke and Zebitz, Japanese port authorities initiated an AGM control 1999). program in 2007 to reduce the AGM population in According to Pogue and Schaefer (2007), EGM ports. is a single subspecies of L. dispar dispar which oc- The evaluation of female AGM flight ability is curs throughout Europe, near to the Ural Moun- important, especially to determine the control area tains, North Africa and introduced into North around ports, because it is likely that the risk of America, while AGM is composed of several egg masses attaching to vessels is strongly related species and subspecies, which occur throughout to the numbers of females attracted to their light temperate Asia, including Japan. Among them, L. sources at night; however, we have insufficient dispar asiatica is distributed widely in continental knowledge on their behavior. Koshio (1996) * To whom correspondence should be addressed at: E-mail: [email protected] DOI: 10.1303/aez.2010.121 121 122 R. IWAIZUMI et al. reported the pre-oviposition behavior of AGM After emergence, they were kept in the department females and clarified that mated females showed until the start of experiments. fluttering, walking, and flight behavior for about Just before the start of each experiment, all fe- one hour after sunset to search for oviposition sites, males were marked on their forewings with an oil and then oviposited during the night. Charlton et marker for individual recognition. Female behavior al. (1999) reported a similar observation of AGM was observed in a net cage (experimental cage: in central Siberia and Germany (an invasive popu- 1.9 m height, 1.3 m width and 2.9 m depth) in- lation). Higashiura (1989a, b) observed that AGM stalled in a greenhouse under natural photoperiodic females chose the height of oviposition sites to conditions. In the center of the experimental cage, avoid predation by birds. we placed a cherry branch (ca. 150 cm in height, We observed virgin and mated AGM female be- 2 cm in diameter) supplied with water, on which fe- havior, especially flight behavior, in a net cage males were placed on day 0 to 2 after emergence. under natural photoperiodic conditions in order to Observing conditions were 25–32°C controlled by evaluate female flight ability to establish effective air-conditioning and the natural day length of May control methods for AGM. We also observed other to August. The sunset time during the experimental nocturnal behavior to obtain an overview of AGM period was 18:40–19:00. Moth behavior was ob- female reproductive behavior. served at intervals of 30–60 min, except for the pe- riod from around 22:00–5:00 (no observations). Night observation (19:00–22:00) was conducted MATERIALS AND METHODS with a portable light (K-1600; Toshiba Co.), taking All observations were conducted at the Research care to avoid directly lighting the female body. Division of the Yokohama Plant Protection Station Observation 1: Behavior of virgin females. in Yokohama City. Most observations were con- Virgin females of 0 d old were placed in the experi- ducted in 2007 and additional data were obtained mental cage on different days and observed until in 2008. 20:00 on July 26, 2007 without mating. Two fe- The moths examined in this study were collected males were placed in the cage in the late afternoon as larvae or egg masses in the field, and reared by on July 24, one in the early afternoon on July 25, feeding them cherry and pear leaves. We collected and the other in the early afternoon on July 26 (see larvae in Yokohama City (35°20ЈN, 139°40ЈE) on Fig. 1). The weather was fine throughout the exper- May 22, 2007 and egg masses in Chiba City imental period. Two virgin females were also used (35°30ЈN, 140°10ЈE) on November 30, 2006. In for the same experiments on May 23–25, 2008. 2007, we reared larvae and pupae in our depart- The weather was cloudy on May 23 and rainy on ment (room temperature, 27–30°C and natural pho- May 24–25. toperiod). In 2008, they were reared outdoors in a In 2007, we observed female behavior for 5 min plastic case with a screen net, or in the insect rear- at hourly intervals during the daytime. From 19:00 ing room (Koito Co., PCSH-3, 20–25°C, 40–80% to 21:00, when females are expected to be more ac- relative humidity (RH), 16L8D) from egg masses tive (Koshio, 1996), we conducted continuous ob- laid by adults of 2007, collected in Chiba only. servation. After 21:00, their behavior was checked Fig. 1. Periodic activities of four virgin females in a net cage in 2007. No male was released in the experimental cage. R: Rest- ing, C: Calling by release of sex pheromone, M: Movement by flight, —: no observation. During the periods highlighted in bold, we conducted continuous observation, whilst we observed female behavior for 5 min at hourly intervals during the daytime. Flight Activity of the Female Gypsy Moth 123 at 21:30 and 22:00. In 2008, we observed female were transferred to the experimental cage installed behavior mainly at dusk: from 19:00 to 21:00 on in a greenhouse. We observed female behavior May 23 and from 19:00 to 20:00 on May 24. Their until 21:00 and recorded the start and end of their behaviors were classified into 3 types: rest, calling flight. In order to check re-flight after the end of by pheromone release, and movement by flight. each observation, the position of each female was Calling was judged by the protrusion of the recorded and checked again in the next morning, pheromone gland at the tip of the abdomen, but in 6:00–9:00 am; however, most (16 virgin and 17 some individuals, it could not be discriminated mated), except two individuals (one virgin and one from rest easily. In those cases, we checked more mated), did not fly around midnight. carefully by spending extra times on assessment. Apart from the above three types of behavior, flut- RESULTS tering and walking were observed before and after flight or independently. We did not record these be- Observation 1: Behavior of virgin females haviors precisely, however, because of the continu- Figure 1 shows the periodic behavioral change ous change from calling to these behaviors. of four virgin females examined in 2007. Virgin fe- Observation 2: Behavior of mated females. males rested for several hours after emergence, and From June 22 to August 12, 2007 and July 14–16, then initiated calling behavior. In the following 2008, we used 21 virgin females, including 3 out of days after emergence, calling behavior was initi- 4 females from observation 1 (Nos. 1, 2, and 4 in ated again in the morning and lasted until late Fig. 1), to observe mating and post-copulatory be- evening. Movements by the flight of virgin females havior. During this observation, one to eight males were observed in a limited period from 19:00 to were always present in the experimental cage.