Entomobrya ligata Folsom, 1924

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 : 37-38

Taxon classification Animalia Collembola Entomobryidae

Entomobrya ligata Folsom, 1924 Figs 25, 26, 39

Description.

Body shape and color pattern. Body oval and cylindrical. Color pattern stable, monomorphic (Fig. 25), always with four transverse bands; two thin regular bands along the posterior margin of Th. 2 and Th. 3 respectively, an irregular, patchy, thick band covering most of Abd. 3, and a highly irregular and sometimes broken band across the medial section of Abd. 4. A small patch of pigment covers Abd. 5 and Abd. 6. Patterns usually consisting of black or dark blue pigment with a yellow background. Dark pigment usually in patches along lateral margins of Th. 2 through Abd. 4. Antennae with purple pigment, darken near apex. Legs usually white, with small purple patches on apical end of femora.

Head. Apical bulb of 4th antennal segment usually bilobed, sometimes multilobed. Long differentiated smooth setae on ventral side of 1st antennal segment ≈3 × short setae. Prelabral setae finely ciliated, seemingly smooth at low magnification under light microscopy. Ornamentation of the distal margin of the labral papillae with single seta or spine-like projections. Lateral appendage of labial papilla E slightly curved, relatively thick and short, extending only ¾ papilla length. Dorsal head macrosetae (Fig. 26A) An3a2, An3a3, A6, M3i, S’ 0, S6, Ps3, Pi1, Pm1i, and Pp2 absent; An’ 0, a short mesoseta located medially between both An0 present. Eyes G and H small and subequal. Eye patch with 3 setae.

Thorax. Th. 2 macrosetae a5, m1, m2, m2i, m4, m4p, and m4i present (Fig. 26B). Th. 3, macrosetae a1, a2, a3, a4, a4i, a5, a5e, a6, a6i, m5, m5i, m6, m6e, and m7 present (Fig. 26C); all posterior macrosetae (series P) present. Zone Pm in both thoracic segments with a moderate number of supplemental macrosetae (Fig. 26B,C).

Legs. Trochanteral organ with triangular setal pattern and up to 17 setae. Unguis with 4 internal teeth; basal teeth located approximately middle of inner claw length.

Abdomen. Abdominal chaetotaxy reduced; no macrosetae variation observed. Abd. 1 with 4 macroseta: a5, m2, m3, and m4 (Fig. 26D). Abd. 2 with 5 macrosetae: a2, m3, m3e, m3ep, and m5 (Fig. 26E). Abd. 3 with 3 macrosetae: m3, pm6, and p6 (Fig. 26F). Abd. 4 with 6 inner macrosetae (Fig. 26G). Mucronal teeth subequal.

Remarks.

This species can be identified by the presence of four transverse bands, head mesoseta An’ 0 present, four macrosetae on Abd. 1, and only three eye patch setae (see Table 2 for additional diagnostic characters). Entomobrya unifasciata sp. n. and Entomobrya neotenica sp. n. are closely related to this species and form the Entomobrya ligata complex, characterized by the presence of only three microsetae in the eye patch, four macrosetae on Abd. 1, and six macrosetae on Abd. 4. Entomobrya ligata can be separated from Entomobrya unifasciata sp. n. and Entomobrya neotenica sp. n. by characters outlined in Table 6.

Entomobrya ligata was described by Folsom (1924) and redescribed by Christiansen (1958b). Both descriptions depict Entomobrya ligata with four dorsal transverse bands (Folsom described five bands; he considered the pigment on Abd. 5 and 6 an additional band), two of which occur on the posterior margins of the Th. 2 and Th. 3, respectively. Samples were originally diagnosed as Entomobrya ligata based on chaetotaxy described by Christiansen and Bellinger (1998). However, Katz et al. (2015) showed that a population from Chester Co., Pennsylvania was highly divergent and genetically isolated from other populations. The Pennsylvania population differs from all other populations by the presence of a dark transverse band along the posterior margin of Th. 2. This dark band is present in all individuals collected in Pennsylvania and absent in individuals from all other localities. The original descriptions by Folsom (1924) and Christiansen (1958b) described Entomobrya ligata as having this band present and noted a lack of additional variations in color form. Multiple type specimens deposited at the INHS were examined; all collected in the state of New York, and all carry a dark band along the posterior margin of Th. 2 (Suppl. material 3: D–G). Therefore, the combination Entomobrya ligata is reserved for populations in which individuals carry the posterior band on Th. 2, whereas populations without this band are referred to Entomobrya unifasciata sp. n. (see below).

Distribution.

Endemic to North America. The species has been reported as having a wide distribution, occurring east of the Mississippi River to the Atlantic coast (Suppl. material 2: I). However, in light of the new circumscription provided above and the possible confusion with Entomobrya unifasciata sp. n., most historical reports are questionable, especially those between the western Smokey Mountains and the Mississippi River. The syntypic series of Entomobrya ligata was collected at different localities in New York State and all fresh material was collected in Chester Co., Pennsylvania, suggesting the species may be restricted to the northeast section of the country.

Material examined.

USA: Syntypes, 1 on slide, Karner, N.Y., 7-14-23 (A. Wolf) INHS Cat. No. 528,351; Cotypes: 1 in vial, Karner, N.Y., July, 14 1923 (A. Wolf); Cotypes: 2 in vial, N.Y., July 8, 1923 (A. Wolf); Syntypes, 1 on slide, Mineola, L. I., N.Y., July 8, 1923 (O. W. Barrett) INHS Cat. No. 528,350; Cotypes, 1 in vial, Roorhesville, N. Y., Aug 30, 1923 (M. S. Leonard); Cotypes: 2 in vial, Roorhesville, N. Y., Aug 30, 1923 (M. S. Leonard). Other material: 1 on slide, 1 in vial, Pennsylvania, Chester Co., Wayne, McKaig Nature Education Center (40.06923,-75.37903), leaf litter, 23.v.2011, AK11-33; 1 on slide Pennsylvania, Chester Co., Wayne, McKaig Nature Education Center (40.06923,-75.37903), bark, 23.v.2011, AK11-34.