Male. Head. Eye bridge 1–2 rows of facets. Antennae unicolour. LW-index of 4^th antennal flagellar segment 1.35–1.6; neck 0.25–0.37 × segment width; Transition of basal part to neck pronounced with hairs shorter than segment width; these hairs of normal strength and adjacent. (Fig. 2d). Colour of neck unicolour. Palpi darkened; palpi short; palpomeres 2. First palpomere of normal shape; with 2–4 bristles and only some sparse sensillae. Second palpomere shortly oval and with 3–5 bristles (Fig. 2f). Thorax. Colour brown. Notum unicolour. Thoracic setae weak; brown. Posterior pronotum bare. Mesothoracic sclerites bare. Legs. Colour yellow-brown. Hind coxae darkened. Hairs on fore coxae bright. Front tibia apically without special structure, however, a comblike structure is visible (Fig. 2c). Front tibial organ bright and unbordered. Tibial setae on hind legs weak, inconspicuous. Tibial spurs of equal length. Claws untoothed. Wings (Fig. 4b). Wings slightly darkened; of normal shape. Wing membrane without macrotrichia. Wing venation weak, with faint m-base. M-fork of normal shape. R₁ inserting clearly before base of m-fork; posterior veins bare; bM bare; r-m bare; bM:r-M 1.46–1.7; st-Cu:bM 0.15–0.4; r₁:r 0.4–0.5; C:w 0.55–0.66. Halteres dark; of normal length. Abdomen. Abdominal setae weak; dorsally brown. Hypopygium (Fig. 2a) concolour with abdomen; 0.7–0.8 × longer than wide. Base of gonocoxites bare; gonocoxites broadly separated; inner margin of gonocoxites broadly extended; inner membrane of hypopygium bare or scarcely setose; elongated setae on valves of hypopygium present. Gonostylus elongate (Figs 2a, b, 3a) 1.7–2 × longer than wide; Inner margin concave; apex tapered. Apical tooth present; as long or longer than subapical megasetae; 1.5–2.5 × longer than broad; strong; with ventral opening containing setae (Figs 2b, 3a, b, c). Awl-like setae absent. Megasetae on inner part of gonostylus present; number of megasetae 3; thick; curved; in one group; Position of lowest megaseta 8–15% from top. Whiplash-hair absent. Tegmen (Fig. 2e) 1–1.3 × longer than broad; equally rounded; normal; Central process absent, setigerous papillae present: apically and centrally located behind tegmen. Field with aedeagal teeth present. Length of ejaculatory apodeme/hypopygium 20–27%; Aeadeagal apical structure absent. Measurements. Body size 1.5–1.8 mm. Hind tibia 0.5–0.6 mm. Wing length 1.2–1.6 mm.

a

b

c

d

e

f

Figure 2.

Enhanced sketches of the important diagnostic characters.

a: Hypopygium (scale: 0.1 mm).  
b: Gonostylus (scale: 0.05 mm).  
c: Fore tibial armature (scale: 0.1 mm).  
d: 3^rd, 4^th and 5^th antennal segments (scale: 0.1 mm).  
e: Tegmen and aedeagus (scale: 0.05 mm).  
f: Palpus (scale: 0.05 mm).  

a

b

c

Figure 3.

Scanning electron images showing the apex of the gonostylus and the enigmatic, semi-complete sheath that appears to house a mass of megasetae within.

a: SEM image of male gonostylus (ventral). Magnification 1300× (6.2 mm working distance).  
b: SEM image of broken gonostylar sheath (ventral) revealing the upper surface of a dense mass of megasetae. Magnification 6000× (6.1 mm working distance).  
c: SEM image of gonostylar tooth, rotated 50 degrees and revealing clearly defined edges of sheath-like process covering megasetae. Magnification 6000× (17.4 mm working distance).  

a

b

Figure 4.

Peyerimhoffia jaschhoforum sp. n., habitus of holotype and wing.

a: Habitus (scale: 1 mm).  
b: Wing (scale: 1 mm).  

P. jaschhoforum (Fig. 4a) is instantly recognizable by its long, drawn-out tegmen (Fig. 2a, e) that extends up to the base of the gonostyles. It also has a characteristic set of megasetae-like bristles (3-4) that are bunched together and slotted into the underside/ventral part of the hollow apical tooth which is reminiscent of an upturned canoe (Figs 2b, 3b, c). On one of the paratypes we examined, the ventromesial sclerotization of the gonostylus was ruptured (Fig. 2b). This forced the megasetae-like bristles out from the sheath-like tooth that normally houses the bristles (Fig. 3b, c). When viewed with a fibre-optic lamp or otherwise, these setae may be visible within the tooth giving the illusion of surface topography/texture on the tooth. P. jaschhoforum can be separated from most similar looking species by the absence of long specialized setae and megasetae on the inner-sides of the gonostyles.

Peyerimhoffia jaschhoforum is named in honour of Catrin and Mathias Jaschhof in recognition of their work on Sciaroidea and who collected provisional specimens from Northern Europe.

Boreal zone of Nearctic Region.

P. jaschhoforum appears to be associated with both early and advanced stages of decaying deadwood. In early stages of decomposition larvae most likely reside underneath the bark as interior wood is still intact. The affinity with deadwood likely explains why this species and other Peyerimhoffia species tend to be collected at and around ground level close to the soil surface (Vilkamaa and Hippa 2005). Peyerimhoffia species also tend to be some of the most minute Sciaridae potentially inferring poor dispersal ability. This suggests that Malaise traps may be relatively inefficient in sampling these species.

P. jaschhoforum appears to be a transitional form between the true Peyerimhoffia species such as P. vagabunda which have reduced palpi and a practically undifferentiated tibial organ and Peyerimhoffia s.l., formerly the Corynoptera crassistylata group. In P. jaschhoforum, the narrowly elongated gonostyles resembles Peyerimhoffia species such as P. thula, P. collina and P. semicurvata. The setigerous papillae behind the tegmen possibly suggests a relation with P. alpina, also belonging to the former Corynoptera crassistylata group sensu Menzel and Mohrig (2000). For these reasons, we placed it in the genus Peyerimhoffia.

In the current concept of Peyerimhoffia sensu Vilkamaa and Hippa (2005), the absence or reduction of long, specialized setae may mislead the observer and suggest P. jaschhoforum is not part of Peyerimhoffia. However, modification on the mesial side of the gonostyles has been found in other enigmatic species, such as P. sepei (Hippa and Vilkamaa 2005). In P. jaschhoforum, we record the first reduction in these specialized setae. When compared to P. alpina, the sole Nearctic Peyerimhoffia species described to date, P. jaschhoforum differs in that the intercoxal area is not fused and the tegmen is narrower and longer. However the absence of long specialized setae at the inner side of the gonostyles isolates this species from all other potential congeners. Given the small size and the absence of recognizable characters, additional genetic characters will be helpful to correctly position P. jaschhoforum in a phylogeny. The interesting makeup of the gonostylar tooth and associated setae merits larger comparisons across the true Peyerimhoffia and Peyerimhoffia s.l. using scanning electron microscopy (SEM). It is possible that Peyerimhoffia as a genus sensu Vilkamaa and Hippa is incorrect. The intermediate characters of P. jaschhoforum further suggests that the genus Peyerimhoffia may be polyphyletic.

The main characters are basically the same as in the nominate subspecies described above. Referring mainly to (Fig. 5), P. j. fennoscandica differs in the following ways:

Figure 5.  

Tegmen of P. j. fennoscandica ssp. n. (scale: 0.05 mm).

• the hypopygium is slightly larger
• the apical tooth is narrower and hooked
• the gonostyles are more tumid
• the intercoxal area is fused and U-shaped
• the first palpomere contains 1–3 bristles
• the tegmen is broader and shorter with darkened lateral edges
• the setigerous papillae are centrally located behind the tegmen when viewing ventrally

The subspecies was named after the region Fennoscandia where it has been collected.

Boreal zone of Palaearctic Region.

The method used to collect specimens of P. j. fennoscandica was non-substrate specific (aspirator and sweep-net). It is therefore difficult to comment on its ecology. As it was found in mixed subalpine forest it appears to be forest associated but any deadwood associations are unconfirmed until more substrate specific sampling is carried out.