Xenasteiidae

Definition

A family of minute acalyptrate flies (Diptera) distinguished by distinctive wing venation: two breaks in the costal vein, M1 reduced and not reaching the wing margin, and a well-developed alula with long fringe. Adults are typically smaller than 2 mm.

Etymology

From Greek xenos (strange, foreign) + asteia (graceful, elegant) + -idae (family suffix), referring to the unusual yet delicate wing structure.

Example

Specimens of Xenasteiidae are rarely collected due to their minute size, but can be recognized under magnification by the interrupted costal vein and the distinctive reduced M1 vein that fades before reaching the wing edge.

Related Terms

• Diptera
• Acalyptratae
• wing venation
• costal vein
• alula
• minute flies
• Sphaeroceridae

Usage Notes

The family is placed in the acalyptrate grade of Diptera, though its exact superfamilial placement has been debated. Identification relies heavily on wing characters; the combination of double costal breaks and reduced M1 is diagnostic. Not to be confused with similar minute families such as Sphaeroceridae or Carnidae, which lack this specific venation pattern.