Agrenia

Fjellberg, Arne & Bernard, Ernest C., 2009, Review of Agrenia Börner, 1906 with descriptions of four new species from North America (Collembola, Isotomidae), Zootaxa 2306, pp. 17-28 : 27-28

Key to the species of Agrenia

1. Mucro withlateral seta absent ....................................................................................................................................... 2

- Mucro with lateral seta present..................................................................................................................................... 9

2. Ventral tube in adults with six or fewer anterior setae on each side............................................................................. 3

- Ventral tube in adults with ten or more anterior setae on each side.............................................................................. 7

3. Subapical seta on dens reaching well beyond tip of mucro ( Fig. 1 A) .......................................................................... 5

- Subapical seta on dens short, not reaching beyond tip of mucro ( Figs. 1 E–G)........................................................... 4

4. Claws very long and slender, claw index 3.0 or more; body setae thin, sparse, uniform; outer dorsal lamella of mucro not prominent ( Fig. 1 F) .................................................................................................. falcula n. sp. (Appalachians)

- Claws shorter, claw index less than 3.0; body setae strong, on head and thorax with mixed short and long setae; outer dorsal lamella of mucro high and distinct ( Fig. 1 G)............................................. tarashchukae n. sp. (Appalachians)

5. Colour deep greenish black; ventral tube without anterior setae.................................................. atroviridis (Rockies)

- Colour olive; ventral tube with or without anterior setae ........................................................................................... 6

6. Antennae no more than 1.8 times the length of head diagonal; anterior setae on ventral tube usually absent, occa- sionally 1–2 on each side; claw index in summer specimens 2.1–2.5, in winter specimens 1.2–1.3 ....................................................................................................................................................................................... riparia (Holarctic)

- Antennae in adults more than 1.8 times the length of head diagonal, in large males up to 2.7 times as long; ventral tube usually with 4–5 anterior setae on each side, rarely absent; claw index 2.8–4.5 (summer) and 2.0–2.7 (winter)..

........................................................................................................................................ parkeri n. sp. (Appalachians) 7. Mucro elongate, apical tooth larger than subapical tooth ( Fig. 6 B); maxilla with short, unmodified lamellae ( Fig. 1 M) ............................................................................................................................................................................... 8 - Mucro short and compact, apical tooth not larger than subapical tooth ( Fig. 1 A); maxilla with long, modified lamellae ( Fig. 1 L)............................................................................................................................. extrema n. sp. (Rockies)

8. Claws long and slender, claw index 2.8 or more; head markedly prognathous; abdominal setae of normal density... ........................................................................................................................................... agilis (Pacific Coast Range)

- Claws shorter, shape normal; claw index 2.3 or less; head shape normal, not markedly prognathous; abdominal setae dense, Isotomurus -like..................................................................................................................... cyanura (Rockies)

9. Ventral tube with fewer than 20 anterior setae on each side; setae along anterior edge of frontoclypeus normal, not differentiated into a "moustache" ............................................................................................................................... 10

- Ventral tube in adults with more than 30 anterior setae on each side; frontoclypeal field with a distinct "moustache" ................................................................................................................................................................ pilosa ( Japan)

10. Mucro short and compact, with narrow ventral lamella .......................................................................................... 11

- Mucro elongate, with broad ventral lamella (as in Fig. 1 E–F) ............................................ lamellosa (Appalachians)

11. Body usually with some segments, or parts of segments, darker than rest; reproductive specimens unmodified ........ ............................................................................................................................................... bidenticulata (Holarctic)

- Body colour uniform, without distinctly darker sections; large reproductive specimens with modified setae on tip of abdomen .................................................................................................................................... polymorpha (Rockies)

Figures

FIGURE 1. A-G, mucro shapes of Agrenia spp. A. A. extrema n. sp., lateral view; B. A. extrema n. sp., dorsal view; C. A. parkeri n. sp., winter form; D. A. parkeri n. sp., summer form; E. A. falcula n. sp., ventral view showing the broad ventral lamella; F. A. falcula n. sp., lateral view; G. A. tarashchukae n. sp. H-K, claws of hind legs. H. A. falcula n. sp.; I. A. tarashchukae n. sp.; J. A. parkeri n. sp., winter form; K. A. extrema n. sp. L-N, maxillae. L. A. extrema n. sp., ventral side (left) and inner side (right); M. A. agilis, inner side; N. A. falcula n. sp., ventral side.

FIGURE 6. Agrenia spp. A-C, mucrones. A. A. tarashchukae n. sp.; B. A. agilis; C. A. falcula n. sp.; D-E. Tips of Ant. IV. D. A. extrema n. sp.; E. A. agilis. Scale bars = 20 μm.