Blakistonia parva, Harrison & Rix & Harvey & Austin, 2018

Harrison, Sophie E., Rix, Michael G., Harvey, Mark S. & Austin, Andrew D., 2018, Systematics of the Australian spiny trapdoor spiders of the genus Blakistonia Hogg (Araneae: Idiopidae), Zootaxa 4518 (1), pp. 1-76 : 55

Blakistonia parva , sp. n.

( Fig. 22 A–L)

Type material. AUSTRALIA: South Australia: Holotype male, Beresford Railway Station , 29°18’15”S, 136°39’00”E, 25–30 September 1995, pitfall trap, D.E.H. Stony Deserts Survey (SAM NN20066 ).

Diagnosis. Males of B. parva can be distinguished from those of all other species of Blakistonia by the absence of prolateral clasping spurs on tibia I and by the presence of two, rather than one, prolateral macrosetae on leg I ( Fig. 22 G–I), and an eye group that is distinctly longer than wide ( Fig. 22D ). Females are unknown.

Description. Holotype male (SAM NN20066). Very small idiopid spider (total length 7.2).

Colour (in ethanol; Fig. 22 A–C): Carapace, legs, pedipalp, sternum, labium and maxillae uniformly yellow, chelicerae slightly darker ( Fig. 22 A–F); abdomen yellow with seven mottled brown chevrons cover only dorsal abdomen, not laterally ( Fig. 22A, C )

Cephalothorax: Carapace 3.3 long, 2.3 wide, 2.0 high, 1.4 times longer than wide; oval ( Fig. 22A ), caput low, ocular area raised ( Fig. 22C ); cuticle smooth, with pits outward from fovea and both sides of caput; fovea straight; three rows of sparse setae longways behind eye group, additional setae in sparse rows radiating outwards from fovea, fine setae scattered very sparsely across carapaceforming indistinct fringe around lateral margins; 3 setae around eye group and clypeus ( Fig. 22D ). Length of median clypeus less than 1.0; anterior margin slightly convex. Eye group 0.5 wide, 0.7 long, 0.2 of carapace width; anterior eye row strongly procurved, PLE–PLE/ALE–ALE ratio 1.1; posterior eye row straight; AME only slightly smaller than ALE and separated by about diameter of AME; ALE and PLE separated by just over ALE diameter; PME about half of AME, slightly less than half of PLE and almost directly adjacent to PLE ( Fig. 22D ). Labium without cuspules ( Fig. 22F ). Sternum 1.5 long, 1.4 wide, evenly setose; three pairs of very small sigilla, evenly spaced, all very small ( Fig. 22E ). Maxillae without cuspules, with shorter thickened setae in proximal corner ( Fig. 22E, F ).

Legs: sparsely setose; legs II, III and IV without spines; tarsi I and II ventrally swollen; metatarsi and distal tarsi I, II scopulate on ventral surface only ( Fig. 22 G–H). Paired tarsal claws: leg I p4 (4 large), r4 (4 large); leg II p4 (4 large), r4 (4 large); leg III p3 (2 large, 1 small), r4 (4 large); leg IV p3 (3 large), r3 (2 large, 1 small).

Spination: Tibia I with two prolateral macrosetae ( Fig. 22 G–I). All other legs without spines.

Leg and pedipalp measurements: Length of legs IV> I> II> III. Leg I: femur 2.9, patella 1.4, tibia 2.3, metatarsus 1.5, tarsus 1.8, total = 9.9. Leg II: femur 2.7, patella 1.3, tibia 2.1, metatarsus 1.6, tarsus 1.4, total = 9.1. Leg III: femur 2.1, patella 1.1, tibia 1.4, metatarsus 1.6, tarsus 1.2, total = 7.4. Leg IV (right): femur 2.9, patella 1.3, tibia 2.7, metatarsus 2.6, tarsus 1.6, total = 11.1. Pedipalp: femur 1.6, patella 0.9, tibia 1.6, tarsus 0.9, total = 5.0.

Pedipalp: All segments without spines; tibia short, incrassate, RTA slender, pointed, covered in long setae and thick, short, dense spinules, latter organised in rough ‘rows’ on apophysis and continue in line about as wide apophysis about halfway toward distal edge of tibia, becoming sparser towards distal edge of tibia; long, erect setae on ventral tibia; bulb uniform, globular; embolus simple, slender, tapering, only twisted distally, ca. 1.5 times the length of bulb; cymbium covered in rows of short, sparse spinules, becoming longer closer to distal edge ( Fig. 22 J– L).

Abdomen: Setose, oval, dorsal sigilla not evident; 3.9 long, 2.7 wide ( Fig. 22A ).

Variation: None.

Etymology. The specific name is taken from the Latin parvus (meaning ‘small’), as it is the smallest of all known Blakistonia species.

Distribution. Blakistonia parva is known only from Beresford Railway Station, off the Oodnadatta Track in northern South Australia ( Fig. 32 ).

Remarks. The male was collected in 1995 as part of the South Australian Department for Environment and Heritage’s ‘Stony Deserts Biological Survey’ (see Brandle 1998).

Figures

FIGURE 22. Blakistonia parva sp. n., holotype male (SAM NN20066): A, habitus, dorsal view; B, habitus, ventral view; C, habitus, lateral view; D, eye group, dorsal view; E, sternum, ventral view; F, maxillae and labium, ventral view; G, left leg I, prolateral view; H, left leg I, macrosetae, prolateral view; I, left leg I, ventral view; J, left pedipalp, prolateral view; K, left pedipalp, retrolateral view; L, left pedipalp, proventral view. Scale bars = 2 mm (A, G), 1 mm (J).

FIGURE 32. Distributions of Blakistonia species: B. birksi sp. n. (black circles), B. maryae sp. n. (white circles), B. tunstilli sp. n. (white triangle), B. newtoni sp. n. (black square), B. pidax sp. n. (black triangle) and B. parva sp. n. (white square).