Willow Rose Gall Midge

Rabdophaga rosaria · Order: Diptera · Family: Cecidomyiidae

No source yet on danger. We have no source yet on whether it bites, stings or damages anything.
Willow Rose Gall Midge
Photo: Connie Taylor, CC BY

Each willow gall contains a single pinkish larva that actually pupates inside the gall. The insect lives on willow branches and develops from May-June to August-September while the leaves stay green. Genetic studies show two main clades, with one split further into subclades 2A and 2B, and a close relative, R. strobilina, lives inside its galls.

Source: Wikipedia

How to recognize it

Each rosette holds a single pinkish larva that pupates within the gall.

Source: Wikipedia

Where it lives

Rabdophaga rosaria is found on willow branches.

Source: Wikipedia

When you see it

The gall-midge is active from spring through late summer, maturing before the leaves turn brown.

Source: Wikipedia

Where it comes from

Mitochondrial DNA shows the species splits into two clades, with clade 2 further divided into subclades 2A and 2B.

Source: Wikipedia

Lookalikes

Rabdophaga strobilina is a close relative that lives as an inquiline inside the galls of R. rosaria.

Source: Wikipedia

Where it is found in the US

Recorded in 9 of 51 states and DC. Most records: Alaska, California, New York, Vermont, Minnesota, Oregon, Pennsylvania, Arizona.

Darker = more records. Counts are museum and citizen-science records, not population size.

Source: GBIF

Status: native in North America; native in Canada. Source: iNaturalist

Months it is reported in the US

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Source: GBIF

More photos

Willow Rose Gall Midge photo 3
Photo: Eric Knight, CC BY
Willow Rose Gall Midge photo 4
Photo: Connie Taylor, CC BY
Willow Rose Gall Midge photo 5
Photo: Jonas Katona, CC BY
Willow Rose Gall Midge photo 6
Photo: Mary K. Hanson, CC BY

Questions people ask

When do the willow galls appear?

They begin forming in May-June and are fully developed by August-September while the leaves stay green.

Source: Wikipedia

What trees are affected by this midge?

It lives on willow branches.

Source: Wikipedia

What does the gall look like?

Each gall is a rosette that contains a single pinkish larva which pupates inside the structure.

Source: Wikipedia

Same family (Cecidomyiidae)

Willow Pinecone Gall MidgeWillow Pinecone Gall MidgeRabdophaga strobiloidesOak Leaf Gall MidgeOak Leaf Gall MidgePolystepha pilulaeGoldenrod Bunch Gall MidgeGoldenrod Bunch Gall MidgeRhopalomyia solidaginisOcellate Gall MidgeOcellate Gall MidgeAcericecis ocellarisLarge Creosote Gall MidgeLarge Creosote Gall MidgeAsphondylia auripilaGiant Goldenrod Bunch Gall MidgeGiant Goldenrod Bunch Gall MidgeRhopalomyia capitata

Sources

  • Wikipedia: https://en.wikipedia.org/wiki/Rabdophaga_rosaria

Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia

Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.

How this page works

This is one bug's fact sheet. The colored box at the top says whether it is dangerous. Sections below cover how to recognize it, whether it is a pest, and how to deal with it. The US map shows which states have records; tap a state to see other bugs there.

Every fact on Bug FAQ comes from a named source (university extension sites, government agencies, GBIF, iNaturalist, Wikipedia). The source is linked next to each section. If we have no source for something, we leave it out.