Head. Eye bridge 2–3 rows of facets. Antenna with scape and pedicel brightened. LW-index of 4^th antennal flagellar segment 2.65; neck 0.35 × the segment width (Fig. 2d); some pale sensillae present. Transition of basal part to neck pronounced. Neck unicolour. Antennal setae shorter than segment width; of normal strength; sparse; salient. Palpus bright; with three palpomeres. First palpomere of normal shape; with 2 bristles; with only some sparse sensillae, or with delimited sensillary field. Second palpomere short oval. Third palpomere as long as first segment. Thorax. Colour reddish, bicolour. Notum partially brightened. Thoracic setae long and strong, or normal; black. Mesonotum with some weaker central bristles. Posterior pronotum bare. Mesothoracic sclerites bare. Legs. Colour yellow-white. Hind coxa of same colour as femur. Hairs on fore coxa black. Front tibia apically with a distinct, delimited comb (Fig. 2e). Tibial comb undivided, with 7–8 bristles. Setae of front tibial organ bright. Front tibial organ distinctly bordered. Tibial setae on hind legs weak, inconspicuous. Tibial spurs of equal length. Claws untoothed. Wing (Fig. 2f). Slightly darkened; of normal shape. Wing membrane without macrotrichia. Wing venation weak, with faint stM. M-fork of normal shape. R₁ ending clearly before base of m-fork; posterior veins with macrotrichia; stM bare; CuA₁ with and CuA₂ without macrotrichia; bM bare; r-m with a few setae; bM:r-M 1.1; st-Cu:bM 0.7; R₁:R 0.47; c:w 0.7. Halter dark; of normal length. Abdomen. Abdominal setae strong and dense; tergal setae black; sternal setae black. Hypopygium (Fig. 2a) brighter than abdomen; 0.62 (0.55–0.70) × longer than wide. Base of gonocoxite with normal, weak hairs; gonocoxites fused; inner margin of gonocoxite narrowly U-shaped; inner membrane of hypopygium bare; elongated setae on valves of hypopygium absent. Gonostylus (Fig. 2b) elongate; 3.6 × longer than wide; Inner margin straight, or convex; apex tapered. Apical tooth present; as long or longer than subapical megasetae; ca. 5.6 × longer than wide; strong. Megasetae present subapically; number of megasetae 5; thick; curved; in one group; Posososition of basalmost megaseta 36 (32–40) % from top. Tegmen (Fig. 2c) nearly as long as broad; equally rounded; central process absent. Length of ejaculatory apodeme about 15 % of hypopygium; Aeadeagal apical structure absent. Field with aedeagal teeth present. Measurements. Body size ca. 2.2mm. Hind tibia length 1.05 mm. Wing length 2.0 mm.

a

b

c

d

e

f

Figure 2.

Ctenosciara alexanderkoenigi sp. n.

a: Hypopygium, scale 0.1 mm
b: Gonostylus, scale 0.1 mm
c: Tegmen, scale 0.1 mm
d: 4^th antennal flagellomere, scale 0.1 mm
e: Tibial organ, scale 0.1 mm
f: Wing, scale 1 mm

This beautiful species is conspicuous among the European species of Ctenosciara by its eye-catching and contrasting coloration (Fig. 3). Ctenosciara lutea is also colorful, but more or less completely orange, whereas Ctenosciara hyalipennis and Ctenosciara exigua are bright brownish just like many other Sciaridae. The male hypopygium conforms to the simple structure of the other European species, although the megasetae are more prominent. The new species also differs from all other European species in having a completely bare stM and CuA₂ and a continuous, undivided tibial comb. The similar New Zealand species Ctenosciara nigrostyla (Mohrig, 1999) differs in having a less colourful hypopygium and a straighter gonostylus with a shorter apical tooth.

Figure 3.

Ctenosciara alexanderkoenigi sp. n., habitus photograph, scale 1 mm.

The new species is named in honour of the founder of the Koenig museum in Bonn, Alexander Koenig (1885-1940).

Besides the holotype, the species also appears to be present in New Zealand as confirmed by matching COI sequences on BOLD. We have not studied that material as of yet which is deposited in the Biodiversity Institute of Ontario, Canada.

After having seen the conspicuously looking Ctenosciara specimen from the museum's garden in Bonn for the first time, we were convinced of having discovered a new species native to Europe. The yielded COI sequence showed a 7% distance on BOLD to the nearest neighbour from Australia and convinced us furthermore of having an unknown species. After submitting the sequence to BOLD, it was shown to be identical to two other also newly submitted sequences from New Zealand, sharing the same BIN BOLD:ACP7364. Initially having consulted the key to the New Zealand species (Mohrig and Jaschhof 1999), we were inclined to identify our specimen as Ctenosciara nigrostyla Mohrig but a comparison with the type material in the collection of Werner Mohrig (Poseritz, Germany) revealed that the two species are in fact different. A worldwide DNA database like BOLD does not only help to distinguish new and cryptic species, but may also show distribution patterns. Usually more competitive continental species disperse on islands like New Zealand, but apparently the inverse case is also possible. It is a rare occurrence, that a species from the opposite end of the world is represented by a single specimen only and it is not yet clear, whether Ctenosciara alexanderkoenigi has a permanent population in Germany or if it was only introduced casually with plants or soil. Probably the species was recently introduced from the Australasian Region. If it was a permanent member of the European fauna, a striking species like this would likely have been found earlier.

See Salmela and Vilkamaa (2005).

Ctenosciara exigua was described based on several specimens from mires in Central Finland. It was differentiated from Ctenosciara hyalipennis by the evenly broad gonostyli with lacking megasetae at the dorsal side of the apical tooth, the smaller size and less setose CuA₂. However, the most distinctive character, the shorter and roundish tegmen, was not mentioned. In Ct. hyalipennis the tegmen is much longer than wide, nearly triangular. In our material, the number of macrotrichia on CuA₂ varies from 0 to 18 and the tibial comb was also found to be undivided in some specimens. There were usually differences to the original description in every specimen studied. As seen in Fig. 4, showing one of the barcoded individuals, the gonostylus is more tapered and has apical megasetae. One might argue, that our specimens do not exactly match with Ct. exigua. But as they are in the same manner clearly and more different from Ct. hyalipennis, we confidently identify them as Ct. exigua.

a

b

c

d

Figure 4.

Ctenosciara exigua Salmela and Vilkamaa (2005). Specimen ZFMK-TIS-2544914.

a: Gonostylus, scale 0.1 mm
b: Tegmen, scale 0.1 mm
c: Wing, gonostylus, scale 1 mm
d: Tibial comb, scale 0.1 mm

a

b

c

d

Figure 5.

Habitus photos of European Ctenosciara species

a: Ctenosciara lutea, scale 1 mm.
b: Ctenosciara alexanderkoenigi sp. nov., scale 1 mm.
c: Ctenosciara hyalipennis, scale 1 mm.
d: Ctenosciara exigua, scale 1mm

Since the original description from Finland, the species was mentioned again by Heller et al. (2009) from Sweden and therefore it appears to have a Northern European distribution. As the identification of this species is only possible by careful microsopic analysis of the male genitalia and because the most similar species, Ctenosciara hyalipennis, is one of the most common European Sciaridae, it may have been overlooked.

The barcoding results coupled with the fact that Ctenosciara hyalipennis and Ct. exigua (in our understanding) are quite polymorphic raise the question " Is Ctenosciara exigua really a distinct species?" or "Is it only one variant of the former?". In Central Europe, Ct. hyalipennis shows two distinct morphs. The early spring form is larger and has clearly clavate gonostyles, whereas the summer variant is smaller, brighter and the shape of the gonostyles is just as parallel as in Ctenosciara exigua. The summer variant was treated as Ctenosciara thiedei in Thiede (1977), a nomen nudum, which was never officially published. The analysis of the COI did not show any significant differences between both seasonal morphs. The same situation could be present for the Ctenosciara exigua/hyalipennis complex. Recently Kurina et al. (2015) described a species of Mycetophilidae, which is not distinguishable genetically but only differs in the structure of male genitalia. Similarly is imaginable, that Ct. hyalipennis is a species that has only recently invaded from some other part of the world, then successfully occupied different ecological nices, but speciation has not yet progressed to a point where clear genetic differences have taken place. The bifid East-West distribution pattern in Canada (Fig. 6) might be be a reminiscence of two recent, parallel immigrations, which independently started from the eastern and western coasts. All those localities of Ct. hyalipennis are in the vicinity of typical entry points like harbors, airports and bigger cities with massive human activity or spreading already upstream. Geographic distribution of haplotypes underpin this assumption as Neartic population is gentically less diverse than European (Table 1). Keeping in mind, that most of the sciarid sequences (96%) discussed here originated from the Global Malaise Trap Program and thus sequences are only single strand generated, so some of the singletons may reflect in fact sequencing artefacts. Also earlier faunistic studies from North America (Johannsen 1912, Pettey 1918) do not mention this species and it was found neither in historical collections nor in younger material until 2000 (Mohrig pers. comm.). Further morphological, ecological and genetic analyses are needed to shed light on species concepts of Ctenosciara hyalipennis sensu latu. For the moment we propose to continue treating Ctenosciara exigua as a distinct species.

Table 1. Download as CSV 

Geographic haplotype distribution. ENEA = East Nearctic, FIN = Finland, * = Ct. exigua, GER = Germany, NOR = Norway, WNEA = West Nearctic, see also Suppl. material 5

hap	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
ENEA	2711	213	1	1																1
FIN*	2
GER	132	2			14	853	1	1	3	3	5	2	4	2	1	2	1	1	1
NOR	1				2
WNEA	8	79
total	2854	294	1	1	16	853	1	1	3	3	5	2	4	2	1	2	1	1	1	1

Figure 6.

Occurence of Nearctic Sciaridae based on public availaible records on BOLD Suppl. material 1. Localities with Sciaridae (yellow dots) are even distributed, but BIN AAH3983 (black diamond) is restricted to West and East coast only.