Acta Arachnologica
Online ISSN : 1880-7852
Print ISSN : 0001-5202
54 巻 , 1 号
  • Periasamy Alagesan, Jayarama Muthukrishnan
    2005 年 54 巻 1 号 p. 5-12
    発行日: 2005年
    公開日: 2006/05/19
    ジャーナル フリー
    Composition and biomass of the millipede, Xenobolus carnifex population in two huts of Anaiyur village, Madurai were estimated by direct observation. Data on rates of feeding, assimilation and conversion obtained in the laboratory were applied to estimate the rates and efficiencies of energy flow from the reed (Aristida sativa) through the X. carnifex population during 1997-2000. Ecological and exploitation efficiencies increased from 0.289 to 0.480% and 19.5 to 33.7% during the study period. An average of 257,947 kJ/m2/year reed energy was available in the roof. Of this over 25% was channeled through X. carnifex population. The millipede delivered over about 69% of the ingested reed energy as feces, which supported coprophagus insects, which coexisted in the roof. The millipede population lost about 30% of the ingested energy on metabolism and converted at the rate of 943 kJ/m2/year. An energy flow model has been drawn and discussed in the light of information available in the literature.
  • Takahiro Yamanoi, Tadashi Miyashita
    2005 年 54 巻 1 号 p. 13-19
    発行日: 2005年
    公開日: 2006/05/19
    ジャーナル フリー
    To clarify the foraging strategy of nocturnal orb-web spiders, we examined the relationship between prey items and foraging traits in four Neoscona species that spin typical orb-webs. Taxonomic composition of prey differed markedly among species; beetles occupied about 50% of prey in N. punctigera and N. scylla. As beetles are generally heavier than other prey, these differences could be due to the differences in kinetic energy absorption ability of webs and/or web stickiness. Comparison of the sympatric two species (Neosocna punctigera and N. mellotteei) with similar body size supported the above inference; mesh density and silk stickiness were higher in N. punctigera that captured more beetles, while microhabitat and other foraging traits were similar. These results suggest specialization to beetles in some nocturnal orb-web spiders.
  • Nobuo Tsurusaki, Mayumi Takanashi, Nao Nagase, Takashi Shimada
    2005 年 54 巻 1 号 p. 51-63
    発行日: 2005年
    公開日: 2006/05/19
    ジャーナル フリー
    We investigated opilionid fauna of the Oki Islands (Shimane Prefecture) in the Sea of Japan for the first time. As a result, a total of 14 species were collected from the four main islands (12, 4, 4, and 6 species from Is. Dôgo, Is. Nakanoshima, Is. Nishinoshima, and Is. Chiburi, respectively). A list of the species with some taxonomical notes is presented. Opilionid fauna of the islands may be characterized by: 1) the absence of some species which are commonly found in the San'in area of the mainland Honshu such as Gagrellula ferruginea Loman, and Nelima satoi Suzuki; 2) occurrence of some species that indicate the circum-Japan Sea distribution, such as Leiobunum rubrum Suzuki and Melanopa grandis Roewer; 3) occurrence of some species showing geographical differentiation, though there are no endemic forms at the species level; and 4) affinity to the mainland area around Mt. Daisen (Tottori Pref.) rather than mainland areas of the Shimane Prefecture in the species composition; 5) The numbers of species found on the islands generally exceed those expected from the species-area relationship in and around Japanese Islands. Leiobunum wegneri Šilhavý 1976 described from North Korea is newly synonymized with Leiobunum japonicum japonicum Müller 1914. Likewise, Metagagrella damila Šilhavý 1976 and Gagrella crassitarsi Ha et al. 2004, both originally described from Korean Peninsula, are synonymized with Melanopa grandis Roewer 1910. Two Korean species recently recorded under the names Leiobunum rotundum (Latreille 1798) and Leiobunum rupestre (Herbst 1799) by Ha et al. (2004, Korean Arachnology, 20: 53-71) from Korea are misidentifications of Leiobunum japonicum japonicum and Odiellus aspersus (Karsch 1881), respectively.