# Knapweed Gall Fly (*Urophora affinis*)

The Knapweed Gall Fly is a tiny insect that makes special homes called galls on plants. These galls are like little bumps where the fly's larvae grow. They help the plant and the fly live together in a unique way!

- **Category:** [Insects](https://www.snappit.app/explore/categories/insect)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Habitat:** Grasslands

![Knapweed Gall Fly](https://commons.wikimedia.org/w/index.php?title=Special:Redirect/file/Urophora_affinis01.jpg&width=800)

Photo: Attribution · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Urophora_affinis01.jpg)

## Appearance

The Knapweed Gall Fly is a small, stocky fly, typically 3-5mm long, with a brownish-black body that may show a subtle metallic sheen. Its clear wings are distinctively patterned with dark bands or spots, setting it apart from many other small flies. It has short antennae and large compound eyes.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** Arthropoda
- **Class:** Insecta
- **Order:** Diptera
- **Family:** Tephritidae
- **Genus:** Urophora

## Interesting facts

- A tiny larva can live safely inside a plant gall for almost a year!
- Its babies eat plants from the inside out!
- The adult fly's wings have cool dark stripes or spots!
- They are often set free on purpose to fight invasive plants!

## Special abilities

- **Gall Architect:** Knapweed Gall Fly can create a protective plant gall because its larvae induce abnormal growth, sheltering them as they develop.
- **Targeted Herbivore:** Knapweed Gall Fly has special sensors that help them only lay eggs on specific Knapweed species, ensuring their young have the right food.
- **Weed Warrior:** Knapweed Gall Fly can help control invasive weeds because it specifically targets certain Knapweed plants, limiting their spread.

## Measurements & details

- **Wingspan:** 6-10 mm
- **Size:** 3-5 mm
- **Lifespan:** 330-380 days
- **Leg Count:** 6

## Diet & Feeding

Adults may sip nectar, but the larvae eat the nutritious tissues of knapweed plants from inside their galls.

- **Age differences:** Yes, larvae consume plant tissue inside galls, while adults may sip nectar or water.
- **Primary Foods:** Knapweed stem tissue, Knapweed developing seeds, Nectar
- **Foraging Method:** Foraging

## Ecological connections

- **Depends on:** [Spotted Knapweed](https://www.snappit.app/explore/spotted-knapweed) (*Centaurea stoebe*) — Provides food and shelter for larvae within galls.
- **Depends on:** Diffuse Knapweed (*Centaurea diffusa*) — Provides food and shelter for larvae within galls.
- **Parasitizes:** Parasitic Wasp (*Pteromalus calamagrostidis*) — Lays its eggs inside Knapweed Gall Fly larvae.
- **Eaten by:** [Great Tit](https://www.snappit.app/explore/great-tit) (*Parus major*) — Birds sometimes peck open galls to eat the larvae.

## Traits

- [Solitary](https://www.snappit.app/explore/traits/solitary): Solitary animals live alone for most of their lives, only interacting with others for mating or parental care.
- [Grassland](https://www.snappit.app/explore/traits/grassland): Grassland habitats are terrestrial biomes dominated by grasses and herbaceous plants, supporting a variety of grazing animals.
- [Herbivorous](https://www.snappit.app/explore/traits/herbivorous): This trait characterizes organisms whose diet consists entirely or primarily of plant material.
- [Symbiotic](https://www.snappit.app/explore/traits/symbiotic): Describes a relationship between two different species where they live in close association, often benefiting one or both.
- [Miniature](https://www.snappit.app/explore/traits/miniature): Pertaining to species that are significantly smaller than typical or average for their kind.

## Collections

- [Insects](https://www.snappit.app/explore/collections/insects)

## Safety

**Danger:** 1/5 · Very low

It's safe to look at these flies, but don't touch them or the plants they live on.

## Frequently Asked Questions

### How to identify Knapweed Gall Fly?

Look for six legs, antennae, three body sections and the shape of the wings. Beetles have hardened front wings; flies have just one working pair. Tiny insects may need a close view before their group is clear. Insect Identifier: upload a photo and compare the visible details.

### What is Knapweed Gall Fly's wingspan?

6-10 mm

### How big is Knapweed Gall Fly?

3-5 mm

### How long does Knapweed Gall Fly live?

330-380 days

### What does Knapweed Gall Fly eat?

Adults may sip nectar, but the larvae eat the nutritious tissues of knapweed plants from inside their galls.

### Where is Knapweed Gall Fly usually found?

Grasslands

### How does Knapweed Gall Fly hunt?

Foraging

### How many legs does Knapweed Gall Fly have?

6

## More Insects

- [Common Eastern Bumble Bee](https://www.snappit.app/explore/common-eastern-bumble-bee) (*Bombus impatiens*)
- [Spotted Lanternfly](https://www.snappit.app/explore/spotted-lanternfly) (*Lycorma delicatula*)
- [Brown-belted Bumble Bee](https://www.snappit.app/explore/brown-belted-bumble-bee) (*Bombus griseocollis*)
- [Eastern Carpenter Bee](https://www.snappit.app/explore/eastern-carpenter-bee) (*Xylocopa virginica*)

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Source: [Knapweed Gall Fly: Facts & Places to See — Snappit](https://www.snappit.app/explore/knapweed-gall-fly)