Bug FAQWillow Bead Gall Mite
Aculus tetanothrix · Order: Trombidiformes · Family: Eriophyidae
Also called: Willow Gall Mite
The mite makes a rounded green or reddish pouch on the top of a leaf that also bulges on the underside. A slit-like opening on the leaf underside is lined with hairs that stay inside the gall. It has been recorded in several European countries and also in the United States.
Source: Wikipedia
How to recognize it
The gall appears as a green or reddish rounded pouch on the leaf’s upper side and pushes out on the lower side. A slit-like opening on the leaf underside is present; when the gall matures the interior is hairy but the hairs do not stick out.
Source: Wikipedia
Lookalikes
The gall may also be caused by a closely related species, Aculus salicisalbae.
Source: Wikipedia
Where it is found in the US
Recorded in 46 of 51 states and DC. Most records: California, Florida, Texas, Minnesota, Maryland, North Carolina, Virginia, Ohio.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Same family (Eriophyidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Aculus_tetanothrix
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-23.