Monochroa cytisella

Foodplant: May -June in slight swelling in main stem of Pteridium aquilinum. Often next to a side stem, into which is extends its mining, causing it to wither. 
Length: 7 mm in late May described.
Head: Brown. Posterior edged black. Frons black. Stemmatal area black.
Prothoracic shield: Dark brown. Divided by yellowish medial line.
Thoracic legs: Transparent yellowish brown with darker brown marks.
Body: Bright red. Intersegmentally pale orange. White subdorsal spot on anterior of segments A2-A8. Large white lateral spot on A2-A8.
Spiracles: Very small. Brown peritreme.
Pinacula: Insignificant, consisting mainly of a fine black setal spot.
Setae: Translucent brown.
Anal plate: Dark brown.
Prolegs: Vestigial, but functional. Consisting primarily of a very thin colourless transparent planta, which splays outwards. Crochets brown. Anal proleg more developed; yellowish with brownish lateral sclerite.

Comment: The galls are most easily found in May before the fronds have fully expanded to hide the stem. The mid June galls illustrated were mainly vacant, only one injured larva being found in twelve galls. Rearing is difficult because cut bracken rots so quickly. It is suggested that fresh sections of bracken about 10 cm long, and including a side shoot junction, are provided every three days. The larva needs to be removed from the old piece and directed with a fine paintbrush towards a prepared hole in the new piece.
Information and specimens provided by Mr R.J. Heckford for this text are gratefully acknowledged, but any errors are those of IFS.