Hystrignathus rigidus Leidy, 1850

Carreno, Ramon A., 2018, Pinworms (Nematoda: Thelastomatoidea) from Insects Collected in Mississippi, USA, with description of a new species of Protrellus Cobb, 1920 from the Cockroach Ischnoptera deropeltiformis Brunner von Wattenwyl, 1865 (Blattaria: Ectobiidae), Zootaxa 4531 (4), pp. 567-577 : 574

Hystrignathus rigidus Leidy, 1850 (Thelastomatoidea: Hystrignathidae )

Measurements. Females (n=4): Body length 3800 ± 35 (3775–3850); maximum width 178 ± 5 (170–180); buccal cavity 8 ± 1 (8–10); oral annule length 10 ± 2 (9–13); oral annule width 32 ± 1 (30–33); excretory pore 985; esophagus 608 ± 25 (570–620); length of anterior corpus groove 70 ± 2 (68–71); corpus length 466 ± 16 (443–475); corpus maximum width 44 ± 3 (40–45); isthmus 59 ± 7 (50–65); bulb length 83 ± 4 (78–85); bulb width 82 ± 4 (80–88); vulva from anterior end 1933 ± 71 (1850–2005); vulva from posterior end 1868 ± 96 (1770–1950); tail 535 ± 18 (510–550); body width at tail 70 ± 9 (65–80); egg length 109 ± 5 (105–115); egg width 34 ± 3 (30–38); a = 21 ± 1(21–22); b = 6 ± 0.5(6–7); c = 7 ± 0.3 (7); V = 51 ± 2 (49–53).

The specimens found here are consistent with descriptions of H. rigidus in having 16 spines per row on the cuticle of the anterior part of the body. The measurements provided here are consistent with those of Christie (1934), but are, for most characters, larger than those provided in a recent redescription ( Morffe et al., 2015) but smaller than those provided in the original description of the species ( Leidy, 1850). These inconsistencies in measurements also raise questions about the identity of the species described in various studies. Thus, a molecular analysis of specimens of H. rigidus from different localities could yield information on the possible existence of cryptic species.