Euborellia arcanum Matzke & Kocarek

Matzke, Danilo & Kocarek, Petr, 2015, Description and biology of Euborellia arcanum sp. nov., an alien earwig occupying greenhouses in Germany and Austria (Dermaptera: Anisolabididae), Zootaxa 3956 (1), pp. 131-139 : 132-136

Euborellia arcanum Matzke & Kocarek sp. nov.

( Figures 1–14 )

Material examined. Holotype ♂, Germany: Sachsen, Leipzig, Zoo – Gondwanaland, 26.III.2013, Danilo Matzke leg. (coll. NMPC). Paratypes: same label as the holotype, 1 ♀ (coll. NMPC); 1 ♂, 1 ♀ (coll. PKCO), 1 ♂, 1 ♀ (coll. DMCO), 1 ♂, 1 ♀ (coll. SNMD), 1 ♂ (coll. RMLE), 1 ♂ (coll. ZSM), 1 ♂ (coll. SMNS); Austria: Wien, Tiergarten, Schönbrunn, Regenwaldhaus, 20.VI.2013, Jonathan Neumann leg. 1 ♂ (coll. NMPC).

Description. Body blackish brown, shiny; antennae blackish brown with the exception of the typically 2‒3 yellow antennomeres in the span of antennomeres12‒15 (13‒15 in holotype); legs yellowish; forceps reddish brown. Cuticle punctured, shiny; tegmina and wings entirely absent. Total body length without forceps: ♂♂: 14.9–17.6 mm, holotype 15.7 mm; ♀♀: 15.4–17.2 mm. Length of forceps: ♂♂: 3.1–3.9 mm, holotype 3.2 mm; ♀♀: 3.2–3.8 mm.

Male. Head ( Fig. 1 ) same width as length; postfrontal and coronal sutures fine but distinct; frons convex; posterior margin of the head feebly emarginated at the middle. Eyes blackish brown, length approximately 0.75 times that of the head behind the eyes. Antennae with 21 antennomeres (in holotype antennae incomplete, with 19 antennomeres); antennomere 1 long, narrowed basally, widened terminally, as long as antennomeres 2–4 combined; antennomere 2 transverse, wider than long; antennomere 3 longer than antennomere 4. Antennomeres 2–6 cylindrical, other antennomeres conical. All antennomeres pubescent.

Pronotum ( Fig. 1 ) smooth, a little longer than wide, parallel-sided; anterior margin nearly straight; lateral margins straight; posterior margin convex. Median sulcus fine but distinct. Meso- and metanotum transverse, wider than long, smooth, mesonotum posteriorly convex, metanotum broadly emarginate. Median sulcus visible on mesonotum and metanotum. Sternal plates typical for genus. Tegmina and wings entirely absent. Legs comparatively long, uniformly yellowish; femora stout; tibiae covered with thick and fine setae; length of metatarsomere 1 nearly equal to metatarsomeres 2 and 3 combined.

Abdomen ( Fig. 1 ) sparsely punctate. Tergites (with the exception of the ultimate tergite) convex, somewhat widened posteriorly; lateral glandular folds visible on tergites 3‒4. Tergites 7–8 with a low blunt lateral longitudinal ridge, not developed in some specimens. Ultimate tergite transverse, sides convex, slightly narrowed posteriorly, and slightly depressed medially, with a visible median longitudinal furrow; lateral longitudinal ridge rugose, posterior margin in middle slightly concave. Penultimate sternite narrowed posteriorly, with rounded, weakly emarginated posterior margin ( Fig. 2 ). Pygidium flat. Male forceps asymmetrical, right branch more curved in distal fourth than left branch; both branches subcontiguous and stout at base, gradually tapering apically, nearly straight in basal two-thirds, followed by a slight curve inwards; apices gently hooked, inner margin finely crenulated, dorsally trigonal in basal half, depressed posteriorly.

Genitalia ( Figs. 3‒6 ) with short parameres, 1.2 times longer than wide, broadened in middle and narrowed apically, external margin convex, internal margin gently emarginated in basal fourth. Longer genital lobe, 1.8 times longer than length of paramere, with two apical, weakly sclerotized denticulated pads ( Fig. 5 ). Virga very long, approximately 2.5 times longer than the entire body (in holotype 4.6 cm). Tip of the virga and seminal vesicle as seen in Fig. 6 .

Female. ( Figs. 7–9 ). Comparable to male in most characters except penultimate sternite is narrowed posteriorly, with posterior margin broadly rounded ( Fig. 8 ); female forceps have simple and straight contiguous branches ( Fig. 9 ).

Eggs. ( Fig. 10 ). White, smooth, ellipsoid, 1.2 mm length and 0.95 mm width.

Nymphs. 1st instar ( Figs. 11‒15 ) light brown to brown, head darker and shiny, mandibular palps light to yellow-brown, antennae light brown except antennomere 7 white or yellowish, legs light brown to brown, femora dark-striped, last tergite and forceps reddish brown. Head as wide as long, postfrontal and coronal sutures distinct. Pronotum and metanotum dorsal to median sulcus. Nymphs of instars 2‒5 with many characteristics of 1st instar nymph, but differin in body size and number of antennomeres ( Table 1). In addition, the order of the white or yellowish antennomere differing: 2nd instar, antennomere 10; 3rd instar, 12 or 13; 4th instar, 13 or 14; 5th instar, 15 or 16.

Characters Instar

1 2 3 4 5 Adult Number of measured specimens 24 13 8 12 10 15 Head width HW [mm] 0.9 1.0 1.3 1.5–1.6 2.0 2.7 Body length BL [mm] 4–5 6–8 9–10 11– 12 15–18 20–26 Number of antennomeres 8 12 15 17 19 19–21 Differential diagnosis. Euborellia arcanum sp. nov. is an entirely apterous species and differs from all other apterous species of Euborellia in the combination of the following characters: pronotum longer than wide, rectangular, with parallel sides; uniformly yellow legs; characteristic male genitalia with parameres short, slightly longer than broad, with convex external lateral margin and concave internal margin in basal fourth; genital lobe with two apical, weakly sclerotized denticulated pads. Nearctic species Euborellia peregrina (Mjöberg, 1904) and Euborellia antoni (Dohrn, 1864) are similar but differ in shape of the pronotum (widening posteriorly) and shape of the male forceps and genitalia.

Etymology. The name “ arcanum ” is derived from Latin, meaning “the mystery” or “the secret”, and reflects an unknown country of origin as well as manner of introduction into Europe.

Distribution. Unknown. Occurrence in European greenhouses is alien.

Figures

FIGURES 1 – 9. Euborellia arcanum sp. nov. 1. Habitus of male holotype. 2. Male penultimate sternite, ventral view. 3. Male genitalia. 4. Right paramere of male genitalia. 5. Detail of denticulated pads on the tip of genital lobe. 6. Tip of virga with seminal vesicle. 7. Female head and pronotum. 8. Female penultimate sternite, ventral view. 9. Ultimate tergite and forceps of female.

FIGURES 10 – 15. Euborellia arcanum sp. nov. 10. Female with clutch of eggs. 11. 1 st- instar nymph. 12. 2 nd-instar nymph. 13. 3 rd-instar nymph. 14. 4 th-instar nymph. 15. 5 th-instar nymph. All photographs from breeding culture.