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Subspecies
(1) Blasticotoma filiceti filiceti Klug, 1834
(2) Blasticotoma filiceti pacifica Malaise, 1931

Only the nominate subspecies occurs in Germany. According to Liston (2007) Blasticotoma filiceti pacifica is probably a separate species and I agree with this notion. However, I provisionally list it as a subspecies until more information about its status becomes available.


Original description
Klug, 1834 (p. 251)
Klug F (1834). Uebersicht der Tenthredinetae der Sammlung. Jahrbücher der Insectenkunde, mit besonderer Rücksicht auf die Sammlung im Königl. Museum zu Berlin 1, 223-253.

Locus typicus: Tegel (Berlin), Germany. The types (three syntypes) are deposited with the Naturkundemuseum Berlin (Liston 2007).


Synonyms
Synonymy of Blasticotoma filiceti filiceti:

Blasticotoma filiceti Klug, 1834 (p. 251)
Blasticotoma filicis Thomson, 1871 (lapsus or unjustified emendation)
 

Identification
This is the only species of the family in Germany. So far only females have been reported. The body of the imago is between 0.6 to 0.9 cm long and entirely black. The legs are conspicuously yellow.
The older larvae are about 1 to 1.5 cm long, with a greenish white trunk and a yellow-brown head capsule.


Distribution
Because the species is so rare, its distribution is only fragmentarily known. Records exist from Denmark, Germany, Finland, UK, northern Italy, Netherlands, Norway, Austria, Poland, Sweden, Ukraine, Hungary, Russia (European part), Altai mountains, Baikal region. The subspecies B. f. pacifica occurs in eastern Russia and Japan.


Biology
The species is considered to be very rare, but appears to be locally abundant in certain years; this suggests a connection with cycles in population density of braconid and chalcid wasp larvae that parasitize the larvae of Blasticotoma filiceti. While the larvae are regularly found, imagines are apparently very rare and males of the nominate subspecies are unknown (reports to the contrary are based on misidentified other sawfly species). Liston (2007) suggests that the species reproduces parthenogenetically.
The larvae can be found in fern fronds from July to September and the imagines fly from May until the beginning of July. Thus, there is only a single generation per year. Host plants that are mentioned in the literature are: Matteuccia spec., Athyrium spec., Dryopteris spec., Polystichum spec., and (doubtfully) Pteridium aquilinium. The most important host plant appears to be Athyrium filix-femina. Correlating with the ecology of the host plants Blasticotoma filiceti is predominantly found in forests. Some hymenopteran species parasitize the larvae of Blasticotoma filiceti, so far the braconid wasp Shawiana foveolator and the chalcid wasp Tetrastichus rasnitsyni have been reported, the latter so far only in Asia.


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