National Institute for Environmental Studies Invasive Species of Japan Japanese | English
  1. Invasive Species of Japan >
  2. Insects >
  3. Cylas formicarius

Cylas formicarius

Basic information
Scientific name Cylas formicarius

Click to magnify

Common names Sweet potato weevil
Higher taxon Brenthidae, Curculionoidea, Coleoptera
Natural range India or Indochina
Habitat Parasite on tuburous root of Convolvulaceae plants such as sweet potato. Farm area of sweet potato, and sandy beach with Convolvulaceae such as Calystegia soldanella.
Invasion information
Range in Japan Ogasawara Islands, middle to southern part of Ryukyu Archipelago, Osumi Islands (Yakushima, Kuchinoerabujima, Tanegashima, and Mageshima Is.), southern part of Kagoshima Pref. mainland, and Muroto, Kochi Pref. Range in Japan
Origin Possibly Taiwan.
Date The first record in Japan was at Okinawa in 1903 or earlier (in 1903, serious agricultural damage had already occurred). After, this species has spread as follows: Amami Islands 1931; Tokara Islands 1933; Kuchinoerabujima Is. 1951; Tanegashima and Mageshima Is. 1959; Kagoshima mainland 1965; Muroto 1995.
Route Accidental: Hitchhiking on Convolvulaceae plants.
Impact Predation on Convolvulaceae plants. Serious agricultural pest for sweet potato.
Native organism(s) affected: Convolvulaceae plants; Crops (sweet potato)
Regulation in Japan Quarantine Pest. To prevent spread of this species, import of live vines, leaves, tuberous roots, and other underground portions of plants of Ipomoea, Pharbitis, and Calystegia, live tuberous roots and other underground portions of cassava from areas with Cylas formicarius to Japan is prohibited. In addition, transport of above plants from southern (up to 30°N) islands even within Japan is prohibited (only sweet potato can be transported after quarantine inspection and eradication by steaming) by the Plant Protection Law.
Introduced range in other countries Worldwide in tropical area. Entire Southeast and South Asia, eastern Australia, tropical Africa, Madagascar, Caribbean coastal area in North and South America, Antilles, many Pacific and Indian Ocean Islands.
Reference Notes
  • Ecol Soc Jpn (ed) (2002) Handbook of Alien Species in Japan. Chijinshokan, Tokyo (in Jpn)
  • Hayashi et al. (eds) (1984) The Coleoptera of Japan in Color Vol. IV. Hoikusha, Osaka (in Jpn)
  • Kohama & Takahara (2002) Exotic insects in Okinawa. Bull Okinawa Pref Mus. 28, 55-92 (in Jpn)
  • Nakane et al. (1978) Inconographia Insectorum Japonicorum Colore naturali edita Volume II (Coleoptera). Hokuryukan, Tokyo (in Jpn)
  • Plant Protection Station (2011) Quarantine Pest List (The Annexed Table 1 of the amended Enforcement of Ordinance of the Plant Protection Law) (Accessed on 2012-3-29)
  • Plant Protection Station (2012) List of the Import Prohibited Plants (The Annexed Table 2 of the amended Enforcement of Ordinance of the Plant Protection Law) (Accessed on 2012-3-29)
  • etc.
100 of the Japan’s Worst Invasive Alien Species