On the Medically Important Insects in the Danjo Islands, Especially on the Larval Habitats, the Blood-Sucking Habits and Transoceanic Flight of the Blood-Sucking Insects

An entomological survey was carried out from 4th to 9th August, 1972 in Meshima and Oshima of the Danjo Islands which consist of five small islands, Oshima, Kuroki-jima, Nakanoshima, Hanagurijima and Meshima. The islands situate at 32° NL and 128°22' EL in East China Sea, about 170km west from Akune, Kagoshima Kyushu, Japan. The following 16 species of medically important insects were collected, 12 of which were found to be newly recorded from Meshima and/ or Oshima: Anopheles sinensis Wiedemann, Aedes albopictus (Skuse), Aedes nipponicus LaCasse and Yamaguti, Aedes togoi (Theobald), Culex tritaeniorhynchus summorosus Dyar, Lucilia porphyrina Walker, Parasarcophaga misera (Walker), Tricholiproctia seniorwhitei (Ho), Tabanus kanoi Murdoch and Takahashi, Onychostylus pallidolus (Shiraki), Periplaneta japanna Asahina, Periplaneta fuliginosa Serville, Margattea sp., Eobia chinensis Hope, Eobia cinereipennis Motshulsky and Paederus fuscipes Curtis. A considerable number of the larvae of Aedes togoi were found in every brackish pools just above high tide. The female was not a trouble-some biter in the islands. As no plausible mammalian host except two species of rats was found, the main hosts of this mosquito might be wild birds which were abundant in the islands. Tabanus kanoi, the commonest and trouble-some biter in the islands, will take usually a blood meal from the wild bird. On the basis of that a plenty adult were found in the islands and of that all of the five females dissected were parous, it was assumed that Tabanus kanoi might have an ability to produce autogenous eggs before taking the first blood meal as shown in Tabanus iyoensis Shiraki by Watanabe and Kamimura (1971). A considerable number of the larvae of Culex tritaeniorhynchus summorosus and only one pupa of Anopheles sinensis which usually preferred open ground pool, such as paddy-field were found in a cemented water container located in a forest at Meshima. In view of the geographical and meteorological situations of this islands, it seems to be likely that these mosquito might breed only temporarily in the islands. As a matter of fact, two butterflies, Lampides boeticus Linne and Vanessa indica Herbst, one moth, Hypocala subsature Guenee and one dragonfly, Pantala flavescens Fabricius, which were apparently considered to be air-borne insects, were captured in the islands during the period of the present survey