New record of an alien gall midge, Oligotrophus betheli (Diptera: Cecidomyiidae) on a North American Juniperus horizontalis (Cupressaceae) in Japan, with reference to its ecological traits and possibility of further dispersal and host range expansion

On the basis of adult morphological features together with the profile of infestation on the host plant, we identify a gall midge that is responsible for the discoloration of young twig tips of Juniperus horizontalis Moench (Cupressaceae) in Japan to be Oligotrophus betheli Felt (Diptera: Cecidomyiidae). Both O. betheli and J. horizontalis are native to North America. This is the sixth example of an alien gall midge on its alien host plant in Japan. Oligotrophus betheli is redescribed to offer some morphological characteristics that were not given previously. Information on the distribution, host range, life history pattern and daily activity of O. betheli is provided and the possibility of its further dispersal and host range expansion is discussed. A larval parasitoid is identified to the generic level and the effect of spiders that catch adult gall midges in their webs is discussed.