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Invasive Insect Report 2004.02

Scarab beetle, Popillia sp. nr. taiwana (Coleoptera: Scarabaeidae)



This scarab, which looks very similar to the Japanese beetle, Popillia japonica, became very abundant throughout Guam during 2004. Adults are commonly seen feeding on flowers and leaves of various garden plants. A series of adults feeding on Hybiscus in front of the plant inspection station at Tiyan, Guam on May 28, 2004 were sent for identification to the Natural History Museum in London, England. These specimens were identified as Popillia sp. nr. taiwana by M. Kerley.

A different species of Popillia was previously reported on Guam (Schreiner, I. 1991. Sources of New Insects Estabished on Guam in the Post World War II Period. Micronesica Suppl. 3: 5-13): "Popillia lewisii Arrow is a close relative of the Japanese beetle but was found previously only in the Ryuku Islands. It was first observed in 1985 at Anderson Airforce Base in an area close to the flight line. A trapping program run for the last five years has not shown it to be spreading and it is quite rare except in the first year when a spray program with carbaryl was being undertaken to keep the numbers down. That situation may have changed in 1990, however, as trapping which has just resumed after a hiatus of some months shows it to be quite abundant this year."

Pinned specimens from the original Anderson Airforce Base population are stored in the University of Guam collection. These are labelled as P. lewisii and they do not appear to be different from the specimens sent to the Museum of Natural History. An effort will be made to determine if there are one or two species of Popillia present on Guam.

Identification by M. Kerley, Natural History Museum, London:

  • Family Scarabaeidae
    • Subfamily Rutelinae
      • Genus Popillia
        • Species near to taiwana

Identifier's Notes:

It is not possible to identify these specimens to species. Because Guam is a remote island, there are no known indigenous Popillia species occuring there It would seem that the specimens of this species must have been imported into Guam at some time. The closest species appears to be taiwana Arrow. It is not known whether this species occurs outside Taiwan. Some Popillia species are pests of various plants. P. japonica Newm., The Japanese Beetle, for instance, is found throughout most states in the USA even though it is of Japanese origin. Ruteline scarabs generally feed on a variety of small plants and shrubs and are not necessarily specific to certain plant hosts. The larvae feed on roots and the adults feed on leaves and flowers, in some cases causing considerable damage.