Odonata of Yap, Western Caroline Islands, Micronesia1 Donald W. Buden2,4 and Dennis R. Paulson3 Abstract: Fifteen species of Odonata are recorded from Yap, Micronesia—two Zygoptera and 13 Anisoptera. None is endemic to Yap. Hemicordulia lulico oc- curs elsewhere only in Palau, whereas most of the other species are widespread in the western Pacific and Indo-Australian regions. Macrodiplax cora and Tramea loewi, both recorded by Lieftinck in 1962, were the only species not encountered during this study; Tramea loewi remains known in Micronesia only from a single male collected in Yap by R. J. Goss in 1950. Six of the breeding species in Yap that are widespread in Indo-Australia occur no farther east in the Caroline Is- lands except possibly as unusual extralimital records in the cases of Agriocnemis femina and Neurothemis terminata; the four other species reaching only as far east as Yap are Anaciaeschna jaspidea, Agrionoptera insignis, Orthetrum serapia, and Rhyothemis phyllis. Orthetrum serapia is reported from Micronesia for the first time, although a very old single specimen record of O. sabina from Tobi Island may possibly pertain to O. serapia. The odonate fauna of the outer islands of Yap State is poorly known; only six species have been recorded from among four of the 15 island groups. In addition, Tramea transmarina euryale rather than T. t. propinqua was found to be the subspecies occurring in the Chuuk Is- lands, contrary to earlier publications. This study is the sixth in a series of articles Previous Studies on Yap by the authors on the status of Odonata pop- Lieftinck (1962) recorded two species of Zy- ulations in Micronesia, which were last re- goptera (damselflies) and 11 species of Ani- viewed by Lieftinck (1962). Our previous surveys included the islands of Chuuk (Buden soptera (dragonflies) on Yap and described as an endemic and Paulson 2004), Pohnpei (Paulson 2003, Agrionoptera insignis yapensis subspecies. Many of the specimens that Lief- Paulson and Buden 2003), northern Pohnpei tinck examined were collected by Richard J. State atolls (Buden 2004), and Kosrae (Buden Goss during July–August 1950. One and Paulson 2003). The study reported here A. i. reported as collected by Goss in is based largely on new material collected by yapensis November 1952 was probably misdated or D.W.B. on Yap during mid-June to early Au- misattributed. No other Goss specimens gust 2005. mentioned by Lieftinck have that date, and Gressitt (1954) mentioned only 1950 as the year during which Goss visited Yap. Further- more, Dinsmore and Aronson (1997:353) 1 Manuscript accepted 28 June 2006. stated that Goss ‘‘earned his bachelor’s from 2 Corresponding author. Harvard [in 1948], stayed on under the tute- 3 Division of Natural Sciences and Mathematics, Col- lage of Professor Frank Carpenter (and spent lege of Micronesia-FSM, P.O. Box 159, Kolonia, Pohn- one memorable summer as an entomologist pei, Federated States of Micronesia 96941 (e-mail: [email protected]). on the Pacific island of Yap) to earn master’s 4 Slater Museum of Natural History, University (1951) and doctoral degrees (1952).’’ But there of Puget Sound, Tacoma, Washington 98416 (e-mail: is no indication that he revisited Yap after [email protected]). 1950. Lieftinck (1962) also examined specimens Pacific Science (2007), vol. 61, no. 2:267–277 of odonates collected by J. L. Gressitt and : 2007 by University of Hawai‘i Press N. L. H. Krauss during July 1951, August All rights reserved 1952, and October–December 1952, and an 267 268 PACIFIC SCIENCE . April 2007 unstated number of Agriocnemis femina col- 1). Palau and Yap proper are on the eastern lected by J. W. Beardsley during March– edge of the Philippine Plate and consist April 1954. Lieftinck (1962) also included largely of metamorphic rock and andesitic records obtained by Japanese collectors dur- volcanics, whereas the other Caroline Islands ing the 1930s, and which were previously re- (including outer islands of Yap with the ex- viewed by Asahina (1940). ception of Ngulu Atoll midway between Yap More recent information on the Odonata and Palau) are on the Pacific Plate and are of Yap obtained since Lieftinck’s (1962) re- oceanic volcanics or atolls on descending view is almost completely lacking. Schreiner volcanic cones (Munetomo et al. 2001, Des- and Nafus (1989) recorded larvae of nine spe- cantes 2005). cies of odonates in a survey of aquatic insects The mean annual temperature in Yap is during 15–28 September 1988. Tsuda et al. 27C, and the monthly mean varies only by (2003) reported on the entomological results approximately 1C. Mean annual rainfall is of the 2001 Yap Research Expedition by the ca. 300 cm/yr. The wet season is July to Oc- Kagoshima University Research Center for tober (33 cm/month) at which time the pre- the Pacific Islands. Their report mentions six vailing winds are southwesterly, and the dry species of odonates collected on Ulithi Atoll, season (18 cm/month) is November to June but they did not list them and did not men- when northeast trade winds prevail (Adams tion any collections from Yap proper. How- 1997, Dodson and Intoh 1999). ‘‘Typhoons ever, K. Tsuda (pers. comm.) provided an are fairly uncommon, with only three per unpublished list of 12 specimens among year passing within 120 nautical miles, most seven species (plus one identified only as often in May, June, and November’’ (Adams Neurothemis sp.) collected on Yap proper dur- 1997:2). ing 17–29 October. The interior of Yap proper is hilly and covered with a patchwork of forest (mainly in the ravines) and savanna (mainly on the Study Area central plateau and hilltops). Much of the Yap proper (¼ Yap main islands, the geo- land has been modified by centuries of hu- graphic focus of this study) consists of four man occupation and managed as agroforest, closely juxtaposed islands surrounded by a where the native vegetation is partially fringing reef in the West-central Pacific cleared for cultivation (Falanruw et al. 1987, Ocean at 9 33 0 N and 138 09 0 E (Figure 1). Mueller-Dombois and Fosberg 1998). Dod- Excluding the reef area, Yap is approximately son and Intoh (1999) suggested that major 24 km long, 5–10 km wide, and 98 km2; the forest destruction, probably anthropogenic in highest elevation is 178 m at Mt. Taabiywol. origin, began about 3,000 yr ago, and that the Yap is also the name of the largest island now extensive savanna may be an artifact of (55 km2) in the group; the three others are human impact on vegetation and soil. The Rumung (4 km2), Maap (10.6 km2), and 2000 census recorded 5,838 people living on Gagil-Tamil (28 km2). The 6-m-wide and Yap (Division of Statistics, FSM National ca. 300-m-long canal separating Yap Island Government, 2004), but ‘‘as many as 40,000 from Gagil-Tamil was constructed in 1901 to 50,000 people may have lived on Yap during the German administration to assist proper at the beginning of the 19th century access to the northern villages (Adams 1997). [and] stories of this time tell of some The name Yap also applies to Yap State, hardship and hunger, the possible conse- which includes Yap proper along with 15 quence of overpopulation’’ (Merlin et al. atolls and low coral islands that are sparsely 1996:9). distributed over an area that extends to 1,000 The aquatic habitats of Yap, and potential km east of the main islands. Yap, Chuuk, breeding sites of odonates, include streams, Pohnpei, and Kosrae States make up the Fed- ponds, marshes, seepage areas, mangroves, erated States of Micronesia (FSM), which, drainage ditches, roadside rain puddles, taro together with the Republic of Palau to the patches, and phytotelmata. Streams are abun- west, make up the Caroline Islands (Figure dant, but few are perennial; all of those on Odonata of Yap . Buden and Paulson 269 Figure 1. Location map of Yap State islands (dotted rectangle) and surrounding western Pacific islands. Yap Island are dry from a few days to several June–4 August 2005. Specimens were netted months during the year (van der Brug 1983). during walks along roads and footpaths Most streams are shaded by forest canopy for through a variety of habitats on all four is- much of their length, whereas ponds are usu- lands. Specimens were dried in envelopes ally well exposed to sunlight and surrounded and deposited in the D. R. Paulson collection. by open savanna vegetation (Lobban 1989; Terms of abundance relate to encounter rates pers. obs., this study). Brackish-water swamps during this survey unless specified otherwise: dominated by Nypa palms are common in the very common (seen daily in large numbers, lowlands. often several hundred to over 1,000 per day), common (at least 25 encounters on most days), fairly common (approximately 10–25 materials and methods encounters on most days), uncommon (usu- ally no more than 10 sightings per day and A total of 253 adults of 13 species of odo- unobserved on some days), scarce (usually no nates was collected throughout the main is- more than five encounters in a single day and lands of Yap proper by D.W.B. during 12 not encountered on most days). 270 PACIFIC SCIENCE . April 2007 results circular or elliptical patterns above the sur- face of roads, especially shortly after sunrise. Suborder Zygoptera Family Coenagrionidae Anax guttatus (Burmeister) Agriocnemis femina (Brauer) Lieftinck (1962) recorded Anax guttatus The nominate subspecies of A. femina from many islands in Micronesia, but not ranges widely from Asia to Australia and has Yap, the omission of which may have been been recorded in Micronesia from the south- an oversight.