Urophora cardui
species of insect
Urophora cardui or the Canada thistle gall fly is a fruit fly which, contrary to its common name, is indigenous to Central Europe from the United Kingdom east to near the Crimea, and from Sweden south to the Mediterranean.
Distribution
The Canada thistle gall fly has been introduced to North America from Europe to control the population of its host plant, Canada, or creeping thistle, which is an invasive, introduced weed in North America.
Life cycle
The fly starts life as an egg, one to thirty of which are laid on the stems of its host plant, the Canada or creeping thistle (Cirsium arvense), during the host's growing season. After hatching, the larvae burrow into the stem and form a gall (or swelling). The larvae grow to reach 98% of their full adult body weight, and overwinter in the gall in the third larval stage (instar). They pupate in early spring for 24 to 35 days and appear reddish brown. The adult fly then chews a tunnel and escapes from the gall.
This brief starts where responsible research should: with the source description of “Urophora cardui” as species of insect. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the science & nature register because the source frames it as species of insect. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Mar 13, 2026. The linked authority identifier is Q1128552. None of the 0 selected statements returned an explicit reference.
A general summary may omit uncertainty, sample limits or methodological disagreement that is explicit in the technical record. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Urophora cardui” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.