Trachygamasus gerdi, Witaliński, 2017

Witaliński, Wojciech, 2017, A new species of Trachygamasus from Poland, a new definition of the genus, and a key to the world species (Parasitiformes: Parasitidae), Zootaxa 4303 (3), pp. 407-416 : 414-415

Key to adults of Trachygamasus species

Females

1. Central prong of gnathotectum distally widened and bifid or trifid apically........................................ 2

- Central prong of gnathotectum acuminate.................................................................. 6

2. All dorsal setae simple, seta al on palpfemur bifid....................................... T. macfarlanei Costa, 1962

- Some dorsal setae pilose, seta al on palpfemur spatulate.......................................................3

3. Dorsal setae j1 feathered............................................................ T. fallax Holzmann, 1969

- Dorsal setae j1 simple..................................................................................4

4. Opisthonotum with 21 pairs of setae; length to width of opisthonotum ca. 7/12 (0.6)............. T. biplumatus Karg, 1998

- Opisthonotum with 14–18 pairs of setae; length to width of opisthonotum 4/5 to 2/3 (0.7–0.8).........................5

5. Length of idiosoma exceeding 600 µm, opisthonotum bears 15–18 pairs of setae, endogynium ovate in outline, composed of two circular parts fused axially and forming a figure 8.............................. T. ambulacralis ( Willmann, 1949)

- Length of idiosoma less than 500 µm, opisthonotum bears 14 pairs of setae, endogynium mushroom-shaped in outline, com- posed of two circular parts as in T. ambulacralis ......... T. gracilis ( Karg, 1965) (= T. minor Holzmann, 1969 . Karg, 1971)

6. Epigynium regular (equilateral) triangle with straight lateral sides; gnathotectum central prong narrow, similar to lateral ones7

- Epigynium with arcuate lateral sides, central prong of gnathotectum broader and more solid than lateral prongs...........8

7. Sternal setae st2 simple and thin, distance between st2 greater than between st1. Opisthogaster with 7 pairs of setae, length of idiosoma 670–700 µm.......................................................... T. medianus Tichomirov, 1977

- Sternal setae st2 stout, distance between st2 smaller than between st1. Opisthogaster with 8 pairs of setae, length of idiosoma ca. 560 µm........................................................................ T. triangulus Karg, 1978

8. Sternal setae st2 simple, similar to st1, distance between st2 greater than between st1 and st3. Epigynium width greater than length........................................................................... T. pusillus ( Berlese, 1892)

- Sternal setae st2 shorter and thicker than st1. Endogynium hyaline, elongated axially................................9

9. Endogynium narrow, tubular, with separate elliptic anterior part, ca. 90 µm long, extending nearly along the entire length of the epigynium.................................................................... T. borealis Ma & Wang, 1996

- Endogynium cross-shaped, ca. 58 µm long, its length not exceeding half of the length of the epigynium.... T. gerdi sp. nov.