# Thistle Stem Gall Fly (*Urophora cardui*)

The Thistle Stem Gall Fly is a tiny insect that makes special bumps called galls on thistle plants. These galls are like cozy homes for the fly's babies to grow in!

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

![Thistle Stem Gall Fly](https://commons.wikimedia.org/w/index.php?title=Special:Redirect/file/Canada_thistle_gall_fly_%28Urophora_cardui%29_%288988707577%29.jpg&width=800)

Photo: Pavel Kirillov from St.Petersburg, Russia, CC BY-SA 2.0 · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Canada_thistle_gall_fly_%28Urophora_cardui%29_%288988707577%29.jpg)

## Appearance

The Thistle Stem Gall Fly is a small fly with a dark, robust body, often appearing brownish-black. Its most distinctive feature is its wings, which are patterned with dark bands and clear spots, giving them a mottled, checkered look. This wing pattern helps distinguish it from other small flies.

## Taxonomy

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

## Interesting facts

- Baby gall flies munch their way out of their plant home when grown!
- Each thistle gall can hold several baby flies growing safely inside!
- Scientists sometimes use these flies to help control invasive thistles!
- Their nurseries are actually bumps growing right on a thistle stem!

## Special abilities

- **Gall Architect:** Thistle Stem Gall Fly larvae can create sturdy plant galls that shelter and feed them as they grow.
- **Plant Persuader:** Thistle Stem Gall Fly injects special chemicals that trick thistle plants into growing protective galls.

## Measurements & details

- **Wingspan:** 6-10 mm
- **Size:** 3-5 mm
- **Lifespan:** 10-30 days
- **Leg Count:** 6

## Diet & Feeding

Adult flies sip plant nectar, while their larvae feast on the nourishing insides of thistle stems.

- **Age differences:** Adults consume liquid sugars, while larvae feed on solid plant tissue within galls.
- **Primary Foods:** nectar, honeydew, thistle stem tissue

## Ecological connections

- **Eats:** Canada Thistle (*Cirsium arvense*) — Larvae consume stem tissue, forming galls for shelter and food.
- **Parasitizes:** Thistle Gall Wasp (*Eurytoma robusta*) — The wasp lays eggs in the gall, and its larvae eat the fly larvae.
- **Eaten by:** [House Sparrow](https://www.snappit.app/explore/house-sparrow) (*Passer domesticus*) — Birds may pick open galls to eat the fly larvae inside.

## 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.
- [Keystone Species](https://www.snappit.app/explore/traits/keystone-species): Describes a species whose presence and role have a disproportionately large effect on its environment.
- [Miniature](https://www.snappit.app/explore/traits/miniature): Pertaining to species that are significantly smaller than typical or average for their kind.
- [Pollinator](https://www.snappit.app/explore/traits/pollinator): Describes organisms that transfer pollen, enabling the fertilization and reproduction of plants.

## Collections

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

## Safety

**Danger:** 1/5 · Very low

Don't touch the galls without asking an adult, as they are part of the plant's life.

## Frequently Asked Questions

### How to identify Thistle Stem 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 Thistle Stem Gall Fly's wingspan?

6-10 mm

### How big is Thistle Stem Gall Fly?

3-5 mm

### How long does Thistle Stem Gall Fly live?

10-30 days

### What does Thistle Stem Gall Fly eat?

Adult flies sip plant nectar, while their larvae feast on the nourishing insides of thistle stems.

### Where is Thistle Stem Gall Fly usually found?

Grasslands

### How many legs does Thistle Stem 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: [Thistle Stem Gall Fly: Facts & Places to See — Snappit](https://www.snappit.app/explore/thistle-stem-gall-fly)