Entomobrya nivalis (Linnaeus), 1758

Katz, Aron D., Giordano, Rosanna & Soto-Adames, Felipe, 2015, Taxonomic review and phylogenetic analysis of fifteen North American Entomobrya (Collembola, Entomobryidae), including four new species, ZooKeys 525, pp. 1-75 : 43-46

Taxon classification Animalia Collembola Entomobryidae

Entomobrya nivalis (Linnaeus), 1758 Figs 2, 31, 32, 39

Description.

Body shape and color pattern. Body cylindrical. One primary, but variable, color form (Fig. 31): yellow or white background with black, dark brown or purple pigment always forming thin transverse bands along the posterior margin of Th. 3, and Abd. 2 through Abd. 6. Additional transverse bands present or absent on Th. 2 and Abd. 1. Abd. 4 usually with U-shaped or “11” -shaped pattern connecting basally with band along posterior margin. Antennae usually lack dark pigmentation, sometimes with light brown or purple pigment, darkening near the apex.

Head. Apical bulb of 4th antennal segment usually bi- or trilobed. Long differentiated smooth setae on ventral side of 1st antennal segment ≈3 × short setae. Ornamentation of the distal margin of the labral papillae with 3-4 small seta or spine-like projections per papilla (Fig. 2). Labial lateral appendage slightly curved, relatively thick, nearly reaching tip of papilla. Labial triangle chaetotaxy normal, one specimen with a supplemental ciliate seta internal to M1 (one side only). Dorsal head chaetotaxy (Fig. 32A) with macrosetae An’ 0, A3a2, A3a3, M3i, S’ 0, Ps3, Pi2, Pi3, Pm1i, and Pm2 absent; S1 usually present, A6, S6, Ps3, and Pa2 sometimes present. Eyes G and H small and subequal. Eye patch with 5 or 6 setae.

Legs. Trochanteral organ with triangular setal pattern and up to 34 setae. Unguis with 4 internal teeth; basal teeth located approximately 60% of inner claw length. Unguiculus acuminate with small serrations on internal edge.

Thorax. Th. 2 macrosetae a5, m1, m2, m4, m4i, m4pi, and m5 present (Fig. 32B); m2i and m2i2 usually present; m1i and m4p sometimes present; all posterior macrosetae (series P) are present. Th. 3 macrosetae a1, a2, a3, a4, a4i, a5, a6, a7, m5, m5i, m6, and m7 present (Fig. 32C); most posterior macrosetae (series P) present, p3 present or absent. Both thoracic segments with a moderate number of supplemental macrosetae in zone Pm (Fig. 32B,C).

Abdomen. Abd. 1 with 7-10 macrosetae (Fig. 32D). Abd. 2 macroseta a2, a3, m3, m3e, m3ep, and m5 present; m3ei and m3ea usually absent (Fig. 32E). Abd. 3 macroseta a1, m3, am6, pm6, and p6 present (Fig. 32F); a3 usually absent. Abd. 4 with 7-8 inner macrosetae (Fig. 32G). Mucronal teeth subequal.

Remarks.

Entomobrya nivalis can be diagnosed by the presence of a U-shaped or “11” shaped pattern on Abd. 4 combined with the presence of macrosetae head S4i, Th. 2 m5, Abd. 2 m3ep, and Abd. 3 a1, and the absence of Abd. 3 a2 (see Table 2 for additional diagnostic characters). This species has a highly variable color pattern with many intermediate forms that intergrade with Entomobrya atrocincta females, Entomobrya intermedia , and Entomobrya multifasciata . However, Entomobrya nivalis can be separated from these species by chaetotaxy (Table 3) and, with careful consideration, color pattern; the presence of a U-shaped or “11” shaped pattern on Abd. 4 is unique to this species. Therefore, it is critical to evaluate chaetotaxy in addition to color pattern when making a species diagnosis.

It is important to note that the large genetic distances between presumably conspecific individuals ( Katz et al. 2015; Feng Zhang, personal communication), differences in chaetotaxy between populations in North America and Europe ( Jordana 2012), and variable color pattern among populations across its world-wide distribution, suggests that Entomobrya nivalis likely represents a cryptic species complex.

Distribution.

North America and Europe. Records of Entomobrya nivalis in North America are suspect if diagnosed without considering chaetotaxy given the superficial similarities in color form expressed by Entomobrya atrocincta females (See Fig. 9G,H). See Suppl. material 2: L for a distribution map and below for a list of material examined with collection and locality information.

Material examined.

USA: 2 on slides, 50+ in vial, Maine, Hancock Co., Acadia National Park (44.353823,-68.224754), moss, veg. sweep (blueberry, juniper, populus), 17.viii.2011 (E. C. Bernard), #2009-37; 3 on slides, 5 in vial, Pennsylvania, Allegheny Co., Allegheny National Forest, Dewdrop campground (41.83092,-7895937), leaf litter, 8.vii.2008 (S. M. Shreve); 1 on slide, Vermont, Chittenden Co., Red Rock, Locality I (44.44493,-73.23040), leaf litter, 6.vi.2011 (J. Fisher); 2 on slides, Vermont, Chittenden Co., Farrell Park, Locality II (44.44454,-73.20178), leaf litter, 13.vi.2001 (J. Fisher); 1 on slide, Vermont, Chittenden Co., Farrell Park, Locality II (44.44454,-73.20178), leaf litter, 4.vii.2001 (J. Fisher); 2 on slides, Vermont, Chittenden Co., Farrell Park, Locality II (44.44454,-73.20178), leaf litter, 26.vii.2001 (J. Fisher); 1 on slide, Vermont, Lamoille Co., Stowe (44.48377,-72.69859), leaf litter, 24.vii.2001 (J. Fisher); 1 on slide, Vermont, Lamoille Co. (44.54858,-72.79393), DNA ID#: 12-FSVTlam-ni-1; 1 on slide, Vermont, Washington Co., Locality II, Barre (44.19968,-72.50135), leaf litter, 8.vi.2001 (J. Fisher); 2 on slides, Vermont, Washington Co., Locality II, Barre (44.19968,-72.50135), leaf litter, 24.vii.2001 (J. Fisher); 2 on slides, 6 in vial, Vermont, Rutland Co., Green Mountain National Forest, Greendale Recreation Area (43.35112,-72.82225), leaf litter, 10.vii.2008 (S. M. Shreve); 1 on slide, 6 in vial, Wisconsin, Dodge Co., Horicon Marsh National Wildlife Refuge, end of Dike Rd (43.52736,-88.64381), 12.vi.2011, AK11-47; 2 on slides, 7 in vial, Wisconsin, Sauk Co., Devil’s Lake State Park, 0.5mi down Steinke Basin Loop trail (43.4255,-89.71039), 12.vi.2011, AK11-50.