Eurylychnus Bates, 1891

Lay, Stuart, 2023, A taxonomic review of the Australian genus Eurylychnus Bates (Coleoptera: Carabidae: Broscini), Zootaxa 5330 (2), pp. 247-264 : 248

Eurylychnus Bates, 1891

( Figs. 1–7 )

Bates 1891: 285. Sloane 1892: 50 (key to species). Moore et al. 1987: 120–121 (catalogue). Roig-Juñent 2000: 36–38 (description). Häckel et al. 2010: 65–66 (catalogue). Baehr & Will 2019: 90–91; 93 (description).

Type species, by monotypy: Eurylychnus olliffi Bates, 1891 [= Eurylychnus dyschirioides ( Castelnau, 1867) ]

Diagnosis: Eurylychnus can be separated from all other genera of Australian Nothobroscina by having all of the following characters: a seta in the scrobe of the mandibles, a transverse impression behind the eyes and a single supraorbital seta above each eye. Chylnus resembles Eurylychnus in having a transverse impression behind the eyes and a single supraorbital seta above each eye, but Chylnus lack a seta in the scrobe of the mandibles. Percolestus blackburni Sloane is sympatric with E. blagravei Castelnau , however P. blackburni lacks both a transverse impression behind the eyes and a seta in the scrobe of the mandibles. Percosoma lack the transverse impression behind the eyes, have no seta in the scrobe of the mandibles and have multiple supraorbital setae.

Description: Body length 9.9–23.3mm. Body black, legs red to black, mouthparts and antennae piceous to black. Head with a transverse impression behind the eyes; frontal impression begins at the eyes, curving inwards, joining the frontoclypeal suture.Antennae with antennomeres 1 and 2 glabrous, 3 with an apical ring of setae, 4 with pubescence from apical half, all remaining antennomeres pubescent. Eyes with a single supraorbital seta. Mandibles with a seta in the scrobe. Mentum with paramedian foveae; tooth bifid. Submentum with 2–6 setae. Pronotum with 1–5 setae on lateral margins, with posterior angles constricted, rounded or straight. Males with or without squamose setae under protarsi 1–3. Elytra with parascutellar striole isolated or joined to the apical portion of stria 1, with setae present only on the lateral margins in the umbilical series. Abdominal ventrites 3–5 with or without paramedian setae. Hind wings absent. Aedeagus left paramere broad, asetose, with a denticle at the apex; right paramere longer and narrower than the left paramere, with setae on apical half of the ventral margin, sometimes extending onto the dorsal margin and middle of the paramere at the apex. Aedeagus median lobe weakly to strongly curved ventrally, deflected to the right; apex rounded or pointed, with or without a tooth ventrally.

Remarks: In a cladistic analysis by Roig-Juñent (2000), 2 species groups were identified based on morphology (group 1: E. blagravei Castelnau , E. cylindricus Sloane , E. regularis Sloane ; group 2: E. dyschirioides Castelnau , E. femoralis Sloane , E. ovipennis Sloane , E. victoriae Sloane ) and it was found that the two groups were monophyletic and most closely related to Nothobroscus Roig-Juñent & Ball from Chile. However, not all species of Eurylychnus were examined, and the present study has found some of the characters used to be tenuous. In a key to Nothobroscina ( Seldon & Holwell 2019), Eurylychnus are reported as having a vertexal groove without punctures, abdominal ventrites 3–5 without paramedian setae and protarsi with squamose setae. However, this study has found exceptions in these characters: the vertexal grove is punctate in E. dyschirioides ; abdominal ventrites 3–5 lack paramedian setae only in E. blagravei , E. cylindricus , E. regularis and sometimes in E. ovipennis ; squamose setae is present under protarsomeres 1–3 only in males of E. dyschirioides and E. ovipennis . Baehr & Will (2019) erroneously reported that squamose setae under male protarsus did not occur in Eurylychnus . Moore et al. (1987) noted this genus as occurring in New Caledonia, however the specimens collected from there have since been assigned to a new monotypic genus Monteremita Seldon & Holwell (2019) .

Details of the life history and biology are not well documented beyond being flightless nocturnal predators ( Moore et al. 1987; Baehr & Will 2019). While collecting material for this study, the author collected specimens under fallen timber in cool temperate rainforest ( E. cylindricus , E. regularis , E. ovipennis , E. kershawi and E. victoriae ) and Eucalypt Forest ( E. blagravei and E. dyschirioides ) and, with the exception of E. ovipennis , were quite abundant. Specimens of E. cylindricus were kept in captivity where they survived for 6 months from February to August and readily fed on mincemeat, suggesting scavenging could form part of the wild diet. The defensive secretions of E. blagravei and E. dyschirioides were examined by Moore & Wallbank (1968) who detected saturated and unsaturated acids. The larvae of Eurylychnus are poorly documented, although the larvae of E. blagravei have been described ( Moore 1964) and figured ( Lawrence & Ślipiński 2013).

Figures

FIGURE 1. Ventral surface of male protarsi of A, Eurylychnus dyschirioides; B, Eurylychnus cylindricus.

FIGURE 2. Dorsal habitus of A, Eurylychnus blagravei; B, Eurylychnus cylindricus; C, Eurylychnus regularis; D, Eurylychnus victoriae. Scalebars are 2mm.

FIGURE 3. Dorsal habitus of A, Eurylychnus dyschirioides; B, Eurylychnus ovipennis; C, Eurylychnus kershawi; D, Eurylychnus femoralis. Scalebars are 2mm.

FIGURE 4. Male genitalia of Eurylychnus blagravei (A–C): A, left paramere, B, right paramere, C, median lobe left lateral; E. cylindricus (D–F): D, left paramere, E, right paramere, F, median lobe left lateral; E. regularis (G–I): G, left paramere, H, right paramere, I, median lobe left lateral; E. victoriae (J–L): J, left paramere, K, right paramere, L, median lobe left lateral. Scale bars are 0.5mm.

FIGURE 5. Male genitalia of Eurylychnus dyschirioides (A–C):A, left paramere, B, right paramere, C, median lobe left lateral; E. ovipennis (D–F): D, left paramere, E, right paramere, F, median lobe left lateral; E. kershawi (G–I): G, left paramere, H, right paramere, I, median lobe left lateral; E. femoralis (J–L): J, left paramere, K, right paramere, L, median lobe left lateral. Scale bars are 0.5mm.

FIGURE 6. Pronotum of Eurylychnus dyschirioides. PC = pronotal carina; PS = pronotal setae; MI = median impression; PF = pronotal fovea; PT = pronotal tubercle. Scalebar is 1mm.

FIGURE 7. A, Eurylychnus blagravei, with parascuttelar striole isolated from striae 1; B, Eurylychnus victoriae, with parascuttelar striole joined to apical portion of striae 1.