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Holly berry midge

Asphondylia ilicicola[4]

The holly berry midge is a tiny, mosquito-like fly whose maggot lives inside an American holly berry and eats the seed; infested berries never turn red and stay green all winter.[1][2][3]

Group
Insect
Order
Diptera
Family
Cecidomyiidae
US records
11 states
Sources
4 cited
Updated
2026-10-19

No licensed photo of this species is available yet; the identification notes below describe what to look for.

On this page
  1. Identification
  2. Where it lives
  3. Biology
  4. Damage and signs
  5. Health risk
  6. Control
  7. Related profiles
  8. Common questions
  9. Sources

How to identify it

  • Infested berries grow to about normal size but stay green through fall and winter, sometimes with a reddish blush or a lopsided shape.[1][3]
  • Inside you may find a tiny yellow maggot, or later a brown pupa; a papery pupal case may stick out of the berry after the adult leaves.[1][3]
  • The adult is a small, gray, mosquito-like fly about 1/8 inch long.[1][3]

Where it lives

It is reported from American holly, with infestations described in North Carolina and Maryland landscapes.[1][3]

US map: public records from 11 states since 1990 (GBIF).

Biology and life cycle

Adults lay eggs in the young fruit while the petals are still on the flowers, and the maggots feed on the seeds inside.[1][2]

Most berries hold one maggot, which destroys one seed; about a third hold two, and a few hold three.[1]

Maggots spend the winter in the berry and pupate there as the hollies start to bloom the next spring, when the new adults emerge.[1][2]

Damage and signs

  • Infested berries don't ripen or color, and the seeds they hold are destroyed.[1][2]
  • The larvae and an associated fungus keep the berry green, and birds and squirrels eat green berries much less than red ones, which protects the maggots through winter.[2][3]

Health risk

It lives only inside holly berries; NC State and the University of Maryland mention no risk to people.[1][3]

Control

Biological control

Parasitic wasps can become abundant enough in a landscape that the midge population collapses.[1]

Common questions

Why are some berries on my American holly still green in winter?
A holly berry midge maggot is probably inside, eating the seed; infested berries never turn red.[1][3]
What keeps holly berry midges in check?
Parasitic wasps attack the maggots inside the berries and can become abundant enough to make a local midge population collapse.[1]

Sources

  1. NC State Extension, “Holly Berry Gall Midge.” content.ces.ncsu.edu/holly-berry-gall-midge (accessed 2026-10-19)
  2. University of Minnesota research profile (abstract), “Selective avoidance by vertebrate frugivores of green holly berries infested with a cecidomyiid fly (V. Krischik et al., American Midland Naturalist 121, 1989).” experts.umn.edu/en/publications/selective-avoidance-by-vertebrate-frugivores-of-green-holly-berri/ (accessed 2026-10-19)
  3. University of Maryland, Bug of the Week, “Green is good for holly berry midge, Asphondylia ilicicola (Bug of the Week, M. J. Raupp).” bugoftheweek.com/blog/2023/12/18/deck-the-halls-with-boughs-of-holly-adorned-with-cheery-red-and-green-berries-green-is-good-for-holly-berry-midge-asphondylia-ilicicola (accessed 2026-10-19)
  4. iNaturalist, “Asphondylia ilicicola taxon page (order and family).” www.inaturalist.org/taxa/1274244 (accessed 2026-10-06)

Updated 2026-10-19. Built from sourced records. Spot an error? Tell us.