More samples and inquires concerning false Japanese beetle (Strigoderma arbicola) have been received this year than in the recent past. Inquiries have been primarily from eastern and central Iowa. As the name implies, false Japanese beetle is very similar in appearance to the true Japanese beetle. The major difference is the coloration. False Japanese beetles do not have the bright green and copper coloration of the Japanese beetle. They are dark tan to brown though the thorax may appear metallic green on some specimens. False Japanese beetles do not have the five white hair tufts that are prominent on each side of the abdomen of the Japanese beetle. Here is a link to a close-up photo of FJB where these characteristics can be viewed. Also see the photo below.
The BugGuide website uses the common name “sand chafer” which matches very well the locations where we must commonly see this beetle in fields, gardens and lawns. However, the common name “false Japanese beetle” has been used in Iowa for at least the past 50 years! The False Japanese Beetle is moderately common in the state but varies greatly from year to year.
“False” in insect common names usually means "not the real thing." I suppose calling them "Japanese beetle imitators" or "Japanese beetle look-alikes"would be unwieldy. And somehow "fake" isn't quite right either. There should be a better way to say, "similar to."
At least 6 other insects have the official common name beginning with the word "false." The best known in Iowa is the false chinch bug. As far as I know we don’t have the false potato beetle.
The false Japanese beetle feeds on foliage and the larvae are white grubs. But damage is minimal compared to the “real” Japanese beetle.
Read more about the false Japanese beetle on BugGuide.
An article about FJB was published in the Horticulture and Home Pest Newsletter in 1999. Note since 1999 the true Japanese beetle has expanded its range in Iowa to 63 counties (not the 5 listed in the chart).
True Japanese beetles, Papillio japonica, have been reported in most of Iowa. See the second photo below.
False Japanese beetles have dark tan to brown wing covers and lack the white hair tufts along the sides of the abdomen that are apparent in the Japanese beetle.
The "real" Japanese beetle has coppery-brown wing covers and tufts of white hair at the lateral edges of the abdomen.
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