Pseudostilobezzia curtitarsus Borkent & Grogan, 2024

Borkent, Art & Grogan, William L., 2024, A new species of Pseudostilobezzia Wirth & Ratanaworabhan (Diptera: Ceratopogonidae) from Vietnam, Zootaxa 5448 (1), pp. 128-134 : 130-132

Pseudostilobezzia curtitarsus Borkent & Grogan , new species

Figs. 1A–L

ZooBank: urn:lsid:zoobank.org:act:F133588E-C796-4A17-A9F8-64ECA15984F3

Type material: Holotype, female adult on microscope slide, labelled “HOLOTYPE Pseudostilobezzia curtitarsus Borkent & Grogan ♀ ”, “ VIETNAM, Melinh Station for Biodiversity, 21. 39 N, 105.7 E., 10–17-IV-2016, Elijah Talamas, M. Tran & Chang. Malaise/ Pan Trap ” ( USNM) . Paratype: 1 female, labelled as for holotype ( CNCI) .

DIAGNOSIS: Female adult: only species of Pseudostilobezzia with tarsomere 3 on each leg nearly equal or slightly longer than the length of tarsomere 4 ( Figs. 1D–F ). Male, pupa, larva: unknown.

DESCRIPTION: Female adult: Uniformly dark brown (including scutellum, halter), except forefemur somewhat lighter basally, midfemur with basal third lighter, hind femur with very base lighter ( Fig. 1J ). Head ( Fig. 1A ): vertex with transverse sulcus; antennal ratio = 1.00–1.03 ( Fig. 1C ); palpal segments as in Fig. 1B , third segment with capitate sensilla in shallow pit, palpal ratio = 2.00–2.12. Wing ( Fig. 1K ): membrane moderately infuscated; macrotrichia restricted to apex of wing, length = 1.13–1.20; costal ratio = 0.83–0.88; 2 nd cell 1.86–1.97 X longer than 1 st (measuring the extent of membrane). Legs ( Fig. 1D–J ): TR of foreleg = 2.6–2.7, of midleg = 4.2–4.4, of hind leg = 3.2–3.3; ratio of Ta3/ Ta4 of foreleg = 1.09–1.12, of midleg = 0.95–1.10, of hind leg = 0.96–1.00; foretarsomere 5 swollen around basal 0.4 of length, foreclaw/foretarsomere 5 = 1.06–1.09, inner tooth 0.73–0.81 length of foreclaw, midclaw/midtarsomere 5 = 0.62 with stout basal tooth 0.69–0.70 length of midclaw, hind claw/hind tarsomere 5 = 0.55–0.64 with stout basal tooth 0.39–0.45 length of hind claw. Abdomen ( Fig. 1L ): each half of sternite nine strongly developed medially, two large, well-developed spermathecae, third small but nearly spherical.

Eggs (in vivo): very elongate, slender.

Male, pupa, larva: unknown.

DISTRIBUTION AND BIONOMICS: This species is known only from the type locality at the Melinh Station For Biodiversity in northern Vietnam. The two females were collected with a Malaise trap, with pan traps at its base. It is uncertain which sampled the specimens, the Malaise trap head or the pan traps. This field station is at about 60 meters in elevation, with lowland secondary forest and includes several streams with well-developed riparian habitat. The presence of 7–8 well-developed mandibular teeth indicate that females of this species likely feed on other nematocerous Diptera (likely male chironomids) of a similar size Borkent (2024) .

TAXONOMIC DISCUSSION: The three species of Pseudostilobezzia may be identified with the following key:

1. Wing with first radial cell short, the length of the second/first radial cells about 4.8 (measuring the length of membrane in each); costa without an extension beyond apex of R 3; antennal ratio about 1.4; hind claw with elongate basal tooth, about 0.7 the length of the claw................................................................................. P. macclurei

- Wing with first radial cell more elongate ( Fig. 1K ), the length of the second/first radial cells about 1.5–2.0; costa with a short extension beyond apex of R 3; antennal ratio less than 1.1; hind claw with very short basal tooth, about 0.4–0.5 the length of the claw ( Fig. 1F )........................................................................................ 2

2. Palpal ratio = 3.4; tarsomere 3 on each leg about twice the length of tarsomere 4............................. P. wirthi Palpal ratio = 2.00–2.12; tarsomere 3 on each leg nearly equal or slightly longer than the length of tarsomere 4 ( Figs. 1D–F ).......................................................................................... P. curtitarsus

There are further features which distinguish the new species from the two previously described species, P. macclurei and P. wirthi as follow:

- vertex with transverse sulcus in P. curtitarsus and P. wirthi , absent in P. macclurei .

- antennal ratio is 1.00– 1.03 in P. curtitarsus , 0.99 in P. wirthi and 1.41 in P. macclurei .

- the apex of the wing of P. curtitarsus and P. wirthi has macrotrichia and these are apparently absent in P. macclurei .

- the femora of P. curtitarsus are more lightly pigmented basally ( Figs. 1G–I ) while those of P. wirthi and P. macclurei are reported as uniformly brown.

- the subbasal swelling of fore tarsomere 5 of P. curtitarsus ( Fig. 1D ) is similar to that of P. wirthi and is absent in P. macclurei .

- the hind tarsomere 2 of P. curtitarsus have a row of palisade setae which have not been described for the other two species but this should be checked against their type material.

- the hind claw of P. macclurei is proportionally longer than that of both P. curtitarsus and P. wirthi .

ETYMOLOGY: The specific epithet, curtitarsus (short, tarsus) refers to the proportionally short and distinctive third tarsomeres of the female of this species.

Figures

FIGURE 1. Structures of female Pseudostilobezzia curtitarsus. A. Head capsule, in anterior view. B. Left palpus, in anterior view. C. Antenna. D. Foretarsomeres 2–5. E. Midtarsomeres 2–5 (scale as in D). F. Hind tarsomeres 2–5 (scale as in D). G. Foreleg. H. Midleg (scale as in G). I. Hind leg (scale as in G). J. Thorax, lateral view. K. Wing. L. Apex of abdomen, in ventral view.