New York Natural Heritage Program
Ostrich Fern Borer Moth
Papaipema sp. 2 nr. pterisii

Identifying Characteristics [-]
This species is similar to the Bracken Borer (Papaipema pterisii). The adults are generally larger and more richly colored than P. pterisii, and are often still fresh in late September to mid-October.

Characters Most Useful for Identification [-]
The adults must be identified from an actual specimen, not from a field photograph. Some worn adults might not be identifiable, but a series of two or three specimens would aid in the identification. The adults are more richly colored, particularly the brown areas are darker, than almost all specimens of the Bracken Borer (Papaipema pterisii). Most adults of the Ostrich Fern Borer are also larger, compared to the Bracken Borer (Papaipema pterisii) and bracken fern will often be absent, which would also likely rule out the Bracken Borer. The collection date could also be a clue, as this species could still be fresh in late September when the Bracken Borer have become quite worn, or in October when the Bracken Borer would be unlikely at all. The larvae should be reared to adults to be sure, but should be separable from the Sensitive Fern Borer Moth (Papaipema inquaesita) by the lack of extensive pink on the thorax and from Sthenopis auratus (McCabe and Wagner 1989) by the much more prominent brown tubercles and much better developed prolegs. Also S. auratus larvae would probably be much smaller than Papaipema larvae in late summer, since the Hepialid larvae mature in June. S. auratus larvae also line their burrow with silk.

Best Life Stage for Proper Identification [-]
Either adults or larvae could be identified, but only by an expert.

Behavior [-]
The adults are nocturnal, come readily to blacklights, and most likely appear a couple of hours after sunset.

Diet [-]
The larva bore in the lower stems and later roots of the ostrich fern (Matteuccia struthiopteris) and use no other plants. The adults probably feed very little, if at all.
Ostrich Fern Borer Moth Images
click to enlarge
The Best Time to See
The adults emerge mostly after the bracken borer (P. pterisii) and some ostrich fern borers will be fresh as late as mid-October. Several of this species were collected in Columbia County on September 30, 1989. They probably emerge earliest northward. In general, adults should be looked for from about mid or late September to mid-October, but a few emerge earlier, possibly even in late August, but this would be rare. It is not known when the eggs hatch. Fully fed larvae usually remain dormant for a few weeks before pupating.
Reproducing Larvae present and active Eggs present outside adult Pupae or prepupae present
The time of year you would expect to find Ostrich Fern Borer Moth reproducing (red shading), larvae present and active (blue shading), eggs present outside adult (green shading) and pupae or prepupae present (orange shading) in New York.
Similar Species
  • Bracken Borer Moth (Papaipema pterisii)
    The adults are generally smaller and less richly colored than the ostrich fern borer moth.