Robber Fly (abu)
We get these robber flies in the garden throughout the summer. Because of their size, I’m always wary of them (for the sake of the kids!) but it seems that they are beneficial as they prey on other insects (see photos below).
“As their common name implies, robber flies have voracious appetites and feed on a vast array of other arthropods, which may help to maintain a healthy balance between insect populations in various habitats (Joern and Rudd 1982, Shurovnekov 1962). Asilidae adults attack wasps, bees, dragonflies, grasshoppers, other flies, and some spiders.” From: http://creatures.ifas.ufl.edu/beneficial/flies/robber_flies.htm
Order: Diptera; Family: Asilidae; Subfamily: Apocleinae
Species: Promachus yesonicus
length: male 18-28mm, female 22-30mm
Japanese name: shioya-abu
Robber Flies: Page with lots of information about this group of flies (page created by German dipterologist and museum curator).
By chance I just found the homepage of a fellow insect lover in Fukuoka: OSAMU FUKUDA