Competing interest statement
Conflict of interest: the authors declare no potential conflict of interest.
The genus Chaetocladius Kieffer, 1911 includes about 70 species in the world (Ashe & O’Connor, 2012; Makarchenko et al., 2017), and 28 species among them are reported up to date from Europe (Sæther & Spies, 2013).
The genus was divided into in two subgenera, Amblycladius Kieffer, 1923, with a single species and Chaetocladius s. str. In this paper, the subgenus Chaetocladius s. str. is revised in part on the basis of materials from different collection localities in Italian Alps. As a result of our study, four new species: C. aedeagovirgatus sp. nov., C. subalpinus sp. nov., Chaetocladius ticinoi sp. nov. and C. valdostanus sp. nov. are described. The other species belonging to the genus Chaetocladius known to occur in Italy are: C. dentiforceps (Edwards, 1929), C. dissipatus (Edwards, 1929), C. gelidus Brundin, 1956, C. gracilis Brundin, 1956, C. grandilobus Brundin, 1956, C. laminatus Brundin, 1947, C. perennis (Meigen, 1830), C. piger (Goetghebuer, 1913) and C. suecicus (Kieffer in Thienemann & Kieffer, 1916); their distribution in Italy is here given. A key to adult males of all species of the subgenus Chaetocladius s. str. known to occur in Italy is also presented.
Materials and Methods
The adult specimens were collected with a sweep net near rivers, streams and lakes; other adult specimens, pharate pupae and their exuviae - with a drift net; some samples were collected with light traps. The pupae were associated with males based on hypopygia of pharate specimens extracted from exuviae.
The material was preserved in 70% ethanol. The specimens were cleared in 10 % KOH after the separation of wings and rinsed, including wings, in acetic acid, then transferred in xylene:phenol 3:1 (Wirth & Marston, 1968), finally mounted in Canada Balsam on slides. Morphological terminology and abbreviations follow Sæther (1980). All measures are in µm unless otherwise stated.
All the materials studied, including type specimens are deposited in DeFENS, Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente (DeFENS), Università degli Studi di Milano, Italy.
Genus: Chaetocladius Kieffer, 1911
SUBGENUS: Chaetocladius s. str. Kieffer, 1911: 182.
TYPE SPECIES: Dactylocladius setiger Kieffer, 1908 [= Chironomus perennis Meigen, 1830], by subsequent designation of Goetghebuer (1940-1950).
Description based on material examined and collected in Italy.
Medium sized to large species 3.0-3.9 mm, with wing length 2.0-2.4 mm.
ANTENNA. With 13 flagellomeres; groove beginning at flagellomeres, 2 sensilla chaetica present on flagellomere 2 and 3, about 6-8 on terminal flagellomere. Apex without apical seta. Antennal ratio 1.2-1.5.
HEAD. Eyes faintly pubescent with more or less developed microtrichia between ommatidial lenses or naked; with slight wedge-shaped dorsomedial extension. Temporal setae relatively numerous, mostly uniserial; inner verticals sometime separated from outer verticals and postorbitals or not separable. Apex of palpal segment 3 with 5-15 sensilla clavata at distinct and well developed sensillum coeloconicum.
THORAX. Antepronotum well developed, lobes gaping, meeting at a point anterior to scutal projection, with few lateral setae. Humeral pit well developed, but not transparent, mostly ovoid with several smaller pits within one larger spot. Acrostichals short but distinct, starting close to antepronotum; dorsocentrals uniserial or partly biserial; prealars few; supraalars absent. Scutellum with mostly uniserial transverse row of setae.
WING. Membrane without setae, with coarse punctation (microtrichia visible at 40×). Anal lobe not projecting, forming a right angle. Costa barely extended; R2+3 running midway between R1+2, and R4+5, or closer to R1, ending distal to end of M3+4; FCu opposite of RM; Cu, slightly sinuate distally to approximately straight; postcubitus and An ending distal to FCu. R with about 10 setae, R1 with very few setae, R4+5 without setae.
LEGS. Spurs of mid and hind leg tibiae with prominent, projecting, apicolateral denticles. Pseudo-spurs present on tarsomeres 1 and 2 of mid and hind legs, in only one species on tarsomere 1 of fore leg. Sensilla chaetica not found on legs of the examined species. Pulvilli small.
ABDOMEN. Tergites with scattered setae, more dense laterally and often with distinct anterior transverse rows.
HYPOPYGIUM. Anal point variable, but always present and hyaline, very transparent, without setae or with few scattered microtrichia on apex, but with setae and dense microtrichia at base; triangular or parallel-sided; apex pointed or rounded, base and anal point proper separated into 2 distinct parts. Phallapodeme well developed, sometime with hook-shaped anterior apex. Sternapodeme more or less strongly arched, oral projections present or reduced or absent. Virga consisting of cluster of moderately long spines, very weakly sclerotized or absent. Aedeagal lobe present or reduced, in one species very well developed. Gonocoxite with inferior volsella more or less separated into a dorsal and ventral lobe. Gonostylus curved or at right angle, sometimes with distinct outer corner, in one species with a tubercle near the base; crista dorsalis mostly long, low and preapical, megaseta present; 3 megasetae present in one species.
HOLOTYPE: adult male, Italy, Aosta Valley, Veny Valley, spring in Miage garden N 45°47’4.83’’, E 6°53’7.51’’, 9.IX.1995, leg. Rossaro.
Adult male (n=1).
Total length 3.13 mm. Wing length 2.01 mm. Total length/wing length 1.5. Colouration dark brown.
ANTENNA. With 13 flagellomeres; groove beginning at flagellomere 3; 2 sensilla chaetica present on flagellomeres 2 and 3, about 12 on terminal flagellomere. Apex without apical seta. AR 1.28 (last antennal flagellomere: 614 long).
HEAD. Eye with very short pubescence; with a moderate wedge-shaped dorsomedial extension. About 9 temporal setae not separable into inner and outer verticals. Palpomeres 194-204: 113-126: 125-127: 54-57: 24-26. Apex of palpomere 3 with 8 sensilla clavata in subapical distinct and well developed sensillum coeloconicum.
THORAX. Antepronotum moderately or usually well developed, lobes gaping, meeting at a point anterior to scutal projection or occasionally not in contact, with few to several lateral setae. Two humeral pits well developed, mostly ovoid with several smaller pits within one larger spot. 17 acrostichals short but distinct, starting at antepronotum; 9 dorsocentrals uniserial, robust about 120 long; 6 prealars; supraalars absent. Scutellum with 7 setae, uniserial.
WING. Membrane without setae, with coarse punctation (microtrichia visible at 40×). Anal lobe not projecting. Costa barely extended; R2+3 running near to R1+2, R4+5 ending distal to end of M3+4; FCu opposite to RM; Cu moderately curved, postcubitus and An ending distal to FCu. R, R1 and R4+5 with setae. Squama with about 15 setae.
LEGS. Spurs of mid and hind leg tibiae with prominent, projecting, apicolateral denticles. Two pseudo-spurs present on tarsomeres l, 2, 3 of hind legs, and on tarsomere 1, 2 of mid legs, absent on tarsomeres of fore leg. Pulvilli developed. Length (in µm) and proportions of leg segments as in Table 1.
ABDOMEN. Tergites with scattered setae, more dense laterally and often with distinct anterior transverse rows.
HYPOPYGIUM. Anal point very slender about 51-52 long, less than 3.5 wide, without microtrichia; base with setae and dense microtrichia. Phallapodeme well developed, with hook-shaped anterior apex, aedeagal lobe very developed and sclerotized, 45 long. Sternapodeme strongly arched, oral projections reduced. Virga consisting of cluster of moderately long spines about 30 long, weakly sclerotized Gonocoxite 245 long, with well developed inferior volsella; dorsal lobe appearing as a distinct rounded protuberance, well separated from the ventral lobe, visible posterior to dorsal lobe. Gonostylus curved, without distinct outer corner; crista dorsalis mostly long, low and preapical; megaseta present.
The species is near to C. dissipatus, with a very slender anal point, but it differs distinctly in having very well developed stout aedeagal lobes.
HOLOTYPE: adult male, Italy, Aosta Valley, Veny Valley, spring near Rif. Monte Bianco N 45º47’52.57’’, E 6º55’53.58’’, 8.IX.1996, leg. Rossaro.
PARATYPES: adult male, same data as holotype; Italy, Aosta Valley, Veny Valley, Estellette glacier st.2, Spring near Rif. Elisabetta N 45°45’54.26” E 6°50’13.22”, 8.IX.1996; leg. Rossaro; 2 males, 1 pharate pupa male, Italy, Aosta Valley, Val Veny, Col de La Seigne staz 0bis, N 45°45’4.26” E 6°48’23.00” leg. Rossaro; adult male, Italy, Trentino Alto Adige, Adamello Glacier, spring below Vedretta Lobbia, N 46°11’51” E 10°35’30.68”, 12.IX.1990, leg. Rossaro.
Adult male (n=6).
Total length 3.03-3.13 mm. Wing length 2.33-2.41 mm. Total length/wing length 1.3. Colouration dark brown.
HEAD. Eyes with weak dorsomedian extensions. Temporal setae: 7 verticals and 4 postorbitals. Clypeus with 6 setae. Antenna with 13 flagellomeres and well developed plume; AR 1.3. Last antennal flagellomere: 513-545, combined length of other flagellomeres: 420-423. Palps: lengths of palpomeres 2-5: 15-26: 47-52: 117-124: 116-118: 168-214. Third palpomere with 5–6 long sensilla clavata in a subapical sensillum coeloconicum.
THORAX. Antepronotum moderately or usually well developed, lobes gaping, meeting at a point anterior to scutal projection or occasionally not in contact, with few to several lateral setae. Two humeral pits well developed, mostly ovoid with several smaller pits within one larger spot. 17 acrostichals short but distinct, starting at antepronotum; 10 dorsocentrals uniserial, robust about 120 long; 6 prealars; supraalars absent. Scutellum with 8 setae, uniserial.
WING. Membrane without setae, with coarse punctation (microtrichia visible at 40×). Anal lobe not projecting. Costa barely extended; R2+3 between R1+2 and R4+5, R4+5 ending distal to end of M3+4; FCu opposite to RM; Cu moderately curved, postcubitus and An ending distal to FCu. R with 10-13 setae, R1 with 2 setae, R4+5 without setae. Squama with about 6-9 setae.
LEGS. Spur of fore leg tibia 62 long. Spurs of mid tibia 24-28, of hind tibia 61 long. Hind tibial comb with 12 setae. Two pseudospurs present on tarsomeres l, 2 of mid and hind legs, absent on tarsomeres of fore leg. Pulvilli small. Length (in µm) and proportions of leg segments as in Table 2.
HYPOPYGIUM. Tergite IX with 18-21 setae 26-33 long and narrowly triangular anal point 26-35 long and 6 wide at base, with microtrichia present only at base. Distal apex not reaching posterior margin of inferior volsella. Laterosternite IX with 7-9 setae on each side. Transverse sternapodeme rounded, without oral projections. Virga 23 long, consisted of several setae. Gonocoxite 210-220 long; inferior volsella divided into dorsal and ventral lobe; dorsal lobe rounded, with well sclerotized median surface, almost completely covering the ventral lobe. Ventral lobe provided with short setae. Gonostylus 75 long, slender, with right angle outer margin, without subapical crista dorsalis but with two robust setae on well developed tubercle near megaseta, megaseta 8-12 long.
The species can be separated from the other species by the triangular anal point covered with microtrichia, the ball shaped dorsal lobe of inferior volsella, the right angle of gonostylus; it differs from C. gracilis in having a longer anal point, a larger dorsal lobe of inferior volsella and a gonostylus with a right angle outer margin.
Using the key to British Isles (Langton & Pinder, 2007) the choice between points 4 and 5 is not possible because the anal point goes beyond middle part of inferior volsella, but does not reach the posterior margin; following point 4 we will go to C. melaleucus, which has a different anal point and inferior volsella; following point 5 we will go to C. piger, but the anal point is shorter and inferior volsella is different.
HOLOTYPE: adult male, Italy, Lombardia, Ticino river, Boffalora N 45°28’21.12” E 8°47’22.07”, 30.III.1994, leg. Rossaro.
Adult male (n=1).
Large species, total length 3.9 mm. Wing length cannot be measured, because very damaged. Colouration dark brown.
HEAD. Eyes with very short pubescence between ommatidia. AR 1.22, last antennal flagellomere: 497 long; palpomeres: xx: 40:42: 101-108: 78-91: 101-147; 11 temporals, 8 clp.
THORAX: 16 dorsocentrals the last 3 separated by 3 small white spots, the first 4 setae into 2 rows, 10 scutellars in one row.
WINGS: with coarse punctuation; very damaged, squama observable with 10 setae, but the rest of the wing cannot be analysed.
LEGS. Legs broken, some segments lacking. Spur of fore leg tibia 51, mid tibia tarsal segments lost, spur of hind tibia 60 long. Hind tibial comb with 14 setae. One spur visible on tarsomeres 1 of p1, spurs absent in other segments preserved. Small pulvilli present. Length (in µm) and proportions of leg segments as in Table 3.
Hypopygium: TIX with a rectangular dorsal plate, bearing very robust but short spines; anal point large, parallel-sided with rounded apex, 47 long, 7-8 wide, sternapodeme with small oral projection, gonocoxite 290 long, well developed tubercle on gonostylus, the inferior volsella projecting medially and sharply pointed as in Chetocladius acuminatus Brundin, 1956. Gonostylus with characteristic tubercle near gonocoxite connection and three megasetae.
The species has an inferior volsella similar to that of C. acuminatus but it has a different anal point and a developed tubercle at the base of gonostylus; characteristic is also the rectangular plate on TIX, covered with short strong spines.
HOLOTYPE: adult male Italy, Aosta Valley, Val Veny, Col de La Seigne staz 3bis, N 45° 44’ 56.06” E 6°48’41.12”, 7.IX.1996, leg. Rossaro.
PARATYPES: adult male with associated pupal exuviae, same locality as holotype; 14.IX.1997, leg. Rossaro, 2 males Italy, Aosta Valley, Val Veny, Col de La Seigne staz 2bis, N 45°44’56.08” E 6°48’41.10”, 7.IX.1996, leg. Rossaro, adult male sorg Lobbia, N 46°11’51” E 10°35’30.68”, 12.IX.1990, leg. Rossaro.
Adult male (n=5).
Total length 3.50-3.56 mm. Wing length 2.27-2.31 mm. Total length/wing length 1.54. Colouration dark brown.
HEAD. Eyes without microtrichia, but with few short points between ommatidia lenses (pubescent), dorsomedian extension weak; 11 temporal setae not separable into verticals and postorbitals. Clypeus with 10 setae. Antenna with 13 flagellomeres and well developed plume; AR 1.18. Length of ultimate flagellomere: 488. Lengths of palpomeres 1-5: 20-25: 61-73: 73-80: 114-122. Third palpomere with 5-6 sensilla clavata subapically.
THORAX. Antepronotum with few lateral setae. Ac 14-18, beginning close to antepronotum; Dc 8; Pa 4-5; Scts 5, in 1 row.
WING. R with 10 setae, R1 with 1 seta and R4+5 without setae. Costa extension very reduced. Apex of R4+5 at the same distance of M3+4. Cu1 curved in apical quarter. Anal lobe reduced, rectangular-rounded. Squama with 8 setae.
LEGS. Spur of fore leg tibia 52. Spurs of mid leg tibia 18 and 20 long, of hind leg tibia 48-50 long. Hind leg tibial comb with 14 setae. Two pseudospurs present on tarsomeres l, 2 of mid and hind legs, absent on tarsomeres of fore leg. Small pulvilli present. Length (in µm) and proportions of leg segments as in Table 4.
HYPOPYGIUM. Tergite IX with 18-21 long setae. Anal point triangular, 25-45 long, 7 wide at its base without microtrichia, rounded at apex. Laterosternite IX with 5-6 setae on each side. Transverse sternapodeme rounded, without oral projections. Virga 21 long, consisted of several setae. Gonocoxite 200-218 long; inferior volsella in caudal position not well divided into a dorsal and ventral lobe, with a well sclerotized dorsal lobe rounded, and a characteristic posterior undulated margin. Gonostylus 70-72 long, with small subapical crista dorsalis in form of tooth, megaseta 12 long.
The shape of dorsal lobe of inferior volsella is very characteristic possessing a sclerotized undulated margin and allows separation from the presumable closest relative - C. gracilis.
Using the key to British Isles (Langton & Pinder, 2007) at point 4 we will go to C. melaleucus, but the anal point and inferior volsella are different.
C. dentiforceps: adult male Sarca di Genova river, spring below vedretta della Lobbia, N 46°11’51” E 10°35’30.68”, 12.IX.1990 leg. Rossaro, adult male Dora Baltea, val Veny, Col de La Seigne stream st. 1bis N 45°45’4.25” E 6°48’23.1” 14.IX.1997, leg. Rossaro
Note: anal point 17 long rounded at apex
C. dissipatus: adult male Adda river Forni glacier st g N 46°25’8.93” E 10°33’56.17”, 18.IX.2001 leg. Rossaro
C. gelidus: adult male Lombardia Oglio Frigidolfo river, small stream near S. Apollonia, N 46°18’18.95” E 10°29’46.66”, 8.VII.1978 leg. Rossaro, adult male Gallavesa stream, N 45°49’6.97” E 9°27’0.56”, 12.XI.1977, leg. Rossaro
C. gracilis: adult male Vedretta Lobbia, N 46°11’51” E 10°35’30.68”, 12.IX.1990, leg. Rossaro, adult male Settimo Milanese, N 45°28’48.44, E 9°2’47.69”, 3.XII.1977, leg. Rossaro, adult male Abruzzi, Vera spring, N 42°22’10.50” E 13°27’32.09”, 21.IV.1990, 1.V1990, 23VII.1990, 1VIII.1990, 22.VIII.1990, 1.IX. 1990, leg. Rossaro. Note: AR=1.56 anal point triangular 22 24-30 long 10 wide at its base
C. grandilobus: 2 males Lombardia Oglio Frigidolfo river, small stream near S. Apollonia, N 46°18’18.95” E 10°29’46.66”, 18.IV.2014 leg. M. Montagna
C. laminatus: adult male Aso stream st 01 N 42°59’7.57” E 13°28’40.12”, 29.I.1979, 28.III.1979, 17.IV.1980, 15.X.1980, leg. Bareggi, 1 pharate pupa male, Trexenda stream near Dané, N 44°18’4.94” E 8°22’31.35”, 15.I.1997, leg. Zunino, adult male small stream in Elba Isle, N 42°47’11.51” E 10°12’34.00”, 3.I.1980, leg. Rossaro, Lambro river st 01 near Magreglio N 45°55’18.98” E 9°15’44.42”, 20.I.1978, leg. Rossaro.
C. perennis: adult male Lombardia, Oglio river, waterhole in Vezza N 46°14’14.60” E 10°24’27.46”, 16.VII.78, leg. Rossaro, adult male Sarca di Genova river, waterfall Nardis N 46°10’4.19” E 10°40’37.18”, 13.IX.1990, leg. Rossaro, adult male Orta lake near Buccione, N 45°47’59.17” E 8°24’54.79”, 3.II.1978, 1.IV.1994, leg. Rossaro, adult male Brembo river st 01 Cassiglio N 45°58’2.83” E 9°36’53.27”, 23.V.1980, leg. Rossaro, adult male spring near Serina N 45°52’40.72” E 9°43’56.41”, 11.IV.1981, leg. Rossaro, adult male Brembo river Oltre il Colle Ola spring N 45°53’27.60” E 9°46’14.22”, 15.XII.1982, leg. Rossaro, adult male Ticino river near Boffalora N 45°28’16.55” E 8°47’23.56”, 11.II.1993, leg. Rossaro, adult male Abruzzi Tasso stream PN08 N 41°52’0.10” E 13°53’42.49”, 25.5.1978, leg. Rossaro, fontana alto Sangro PNA02, N 41°54’4.86” E 13°44’0.91”, 19.V.1978, leg. Rossaro, Sangro SS 84 Km 41 PNA04 N 41°51’4.14” E 13°46’40.92”, 20.V.1978, leg. Rossaro. Note: anal point 34-39 long 16 wide at its base, sternapodeme with well developed oral projections, aedeagal lobes visible, very slender with hook at apex.
C. piger: adult male, Italy, Lombardia, Lago Maggiore, Angera N 45°46’15.46” E 8°34’34.65”, 2.II.1995, leg. L.Marziali, Varese lake, Schiranna, N 45°47’41.75” E 8°47’29.13”, 10. II.1997, leg. Rossaro, adult male, 1 pupal exuviae, Alserio lake N 45°46’51.88” E 9°12’26.48”, 27.1.2005. Note: anal point 62-66 long 26 wide at its base.
C. suecicus adult male, Italy, val d’Aosta, Lys glacial stream, Gressoney, N 45°50’17.33” E 7°49’5.75”, 1.VII.1987, leg. Rossaro, adult male, Piemonte, Acqualba stream, near Orta Buccione, N 45°48’33.29” E 8°22’8.42”, 3.III.1978, leg. Rossaro, adult male, Lombardia, Oglio river, Vezza N 46°14’14.60” E 10°24’27.46”, 25.III. 1978, leg. Rossaro. Note: anal point with parallel margins rounded at apex, 69 long 8 wide at its base
Key to males of Italian species of Chaetocladius s. str. Kieffer
gonostylus with a tubercle at its base and 3 megasetae at apex (Figure 5F); eyes pubescent; anal point large, parallel sided, rounded at apex ........... C. ticinoi sp. nov.
anal point very slender and delicate in appearance, less than 3 µm wide ........... 3
aedeagal lobe not visible; eyes relatively slightly pubescent ........... C. dissipatus (Edwards)
aedeagal lobe very well developed (Figure 1B), eyes heavily pubescent ........... C. aedeagolobatus sp. nov.
gonostylus with a distinct outer corner; eyes pubescent ........... 5
outer margin of gonostylus produced into a distinct tooth ........... C. dentiforceps (Edwards)
inferior volsella large, clearly double, with ventral lobe well extending beyond dorsal lobe caudally and occupying at least about three-quarters of the inner margin of gonocoxite, virga weak, consisting of some pale setae; eyes naked ........... C. perennis (Meigen)
anal point roughly parallel-sided and apically rounded ........... 8
anal point long, at least 50 µm long, eyes pubescent ........... C. suecicus (Kieffer)
inferior volsella very large, eyes naked ........... C. grandilobus Brundin
anal point long, about 60 µm long and 20 µm wide, extending near to distal margin of inferior volsella; virga developed; inferior volsella with a characteristic semicircular shape; AR 1.54 ........... C. piger (Goetghebuer)
dorsal lobe of inferior volsella with a large rounded median tubercle, ventral lobe not extending caudally beyond dorsal lobe (Figure 3C,D), anal point about 25 µm, pointed at apex Chaetocladius subalpinus sp. nov.
inferior volsella without a typical crest; eyes pubescence very reduced, but visible ........... C. gracilis Brundin
inferior volsella characteristic (Figure 7D,E), with a typical crest on the caudal margin of dorsal lobe, eyes almost naked ........... Chaetocladius valdostanus sp. nov.
Discussion and Conclusions
The genus Chaetocladius was established by Kieffer (1911); Edwards (1929) and Goetghebuer (1940-50) described and illustrated many Palaearctic species; Brundin (1947; 1956) well illustrated the male genitalia of some known species and described new species; a key to British Isles species was more recently presented (Langton & Pinder, 2007).
Unfortunately for many species there are no recent re-descriptions and this makes difficult the identification of some species; as a matter of fact it is emphasized that there are disagreement between descriptions and figures reported by different authors.
For example, the drawing of hypopygium of Chaetocladius melaleucus (Meigen, 1818) reported in Langton & Pinder (2007) does not fit the drawing of Goetghebuer (1940-1950), the species being represented with very different anal points and inferior volsellae, so the two drawings probably belong to different species. Similarly the figure of C. piger reported in Langton & Pinder (2007) with a long anal point does not agree with the figure reported in Makarchenko et al. (2017), with a much shorter anal point. The genitalia of Chaetocladius holmgreni (Jacobson, 1898) drawn in Makarchenko & Makarchenko (2007) do not match with the drawing of Brundin (1956) [sub C. festivus (Holmgren, 1869)]; in Brundin’s drawing the gonostylus is more or less rounded, even if Brundin (1956) describes it as “endglieder distalwärts kräftig erweitert”, in agreement with Makarchenko & Makarchenko (2007) drawing, where a clear right angle outer margin is figured. Another evident disagreement is in the drawing of C. dissipatus given in Brundin (1956) and the ones reported by Edwards (1929), Goetghebuer (1940-1950) and Langton & Pinder (2007); in Brundin (1956) the anal point is not figured as a slender one as pictured in all the other drawings reported for this species.
Another unresolved problem is the separation among C. dentiforceps, C. laminatus, Chaetocladius holmgreni (Jacobson, 1898) and the recently described Chaetocladius purbeckensis Langton & Armitage, 2015; C. dentiforceps is represented with a very pointed outer margin (Edwards, 1929; Langton & Pinder, 2007), while C. laminatus has a gonostylus with right angle outer margin (Brundin, 1956), and a more or less angular shape is observed in C. holmgreni and C. purbeckensis (Langton & Armitage, 2010). The examined specimens from different localities in Italy emphasize that intermediate shapes of gonostylus can be observed. The genetic distance measured between C. laminatus and C. purbeckensis is 7.7%, high enough to support the existence of two different species (Langton & Armitage, 2015).
DNA sequencing of the largest number of species as possible of Chaetocladius will aid to give light to many unresolved problems.