Acaricis Beard & Gerson (Acari: Tenuipalpidae) is a small genus of flat mites with three species described from Australia and New Zealand sedges, family Cyperaceae (Order Poales) (Beard & Gerson 2009; Xu & Zhang 2013). Beard & Gerson (2009) erected the genus based on description of two species: A. plana, collected on Scleria sphacelata F. Muell., and A. danutae, collected on Carex sp., both from Australia. Later, Xu & Zhang (2013) described A. urigersoni, collected on Gahnia lacera (R. Lesson ex A. Rich.) Steud., from New Zealand.

In this article, we redescribe two species, A. montanus (Collyer, 1973) collected on Pimelea sericeovillosa Hook. (Thymelaeaceae; Order Malvales), and A. alpinus (Collyer, 1973), collected on “mat plants on rocks” (indeterminate family), moving them to the genus Acaricis from Tenuipalpus Donnadieu. These two species were described based on specimens collected in New Zealand.

Measurements for the paratypes are given in micrometers (μm). The terminology used follows that of Lindquist (1985) and Mesa et al. (2009). Leg chaetotaxy is adapted from Lindquist (1985), Zhang & Fan (2004), Xu & Fan (2010) and Seeman & Beard (2011). Tarsal setae are presented as the total number followed by the number of solenidia in parentheses.

The paratypes used in the redescription are deposited in the National Insect and Mite Collection, National Museum of Natural History, Smithsonian Institution (NMNH), located in the Systematic Entomology Laboratory (SEL), USDA, Beltsville, Maryland, USA, and at the Natural History Museum (BMNH), located in London, England, UK.

Acaricis Beard & Gerson, 2009: 31; Mesa et al. (2009): 113; Xu & Zhang 2013: 357

Type species Acaricis plana Beard & Gerson, 2009

Female — Body elongate, usually more than twice as long as wide; palpus usually four segmented. Anterior margin of prodorsum with median forked projection forming a notch (elongate in Aust. species; short in NZ species); prodorsum with two or three pairs of setae (sc1, sc2 present; v2 present or absent); setae sc2 lanceolate or acicular. Dorsal opisthosoma with nine pairs of setae: c3, d1, d3, e1, e3, f2, f3, h1 present; setae c1, c2, d2, e2 absent; setae h2 elongate and filiform. Venter with two pairs of 4a setae; setae g1 inserted anterior to g2 on membranous genital flap; setae ps3 inserted far anterior to ps2. Leg chaetotaxy: tarsi I–II with seta ft″ present, ft′ absent; tarsi III–IV with seta ft′ present, ft″ absent; tarsi I–II with seta ft″ and tarsi III–IV with seta ft′ elongate, filiform, inserted on short tubercle; trochanter IV with one seta or nude (seta v′ present or absent). Leg setal formulae (legs I–IV): femora 4-4-2-2 or 4-4-2-1, genua 2-2-1-0 or 2-2-0-0, tibiae 5-5-3-3 or 5-5-3-2; setae d, l′, l″ on femora, genua and tibia I–II thickened, barbed, inserted in lateral position.

Male— tarsi I–II with two solenidia (all species); tarsi III–IV with one solenidion (except A. danutae without solenidia).

All previous known species of Acaricis have a body more than twice as long as wide, while in A. montanus and A. alpinus the body is marginally less than twice as long as wide. However, the lower body lengths presented here for these two species may be due to the age and mounting media of the specimens, and it is possible that the lengths could be longer in freshly mounted specimens, as has been observed by Beard et al. (in press). In the original description, the female A. alpinus is 354 long and 170 wide (approx. 2.1 times longer than wide) (here 290–300, 150–160, 1.8–1.9, respectively) and the male is 292 long and 146 wide (exactly 2 times longer than wide) (here 230, 125, 1.8, respectively). The female A. montanus is 370 long and 216 wide (approx. 1.7 times longer than wide) (here 330–360, 190, 1.7–1.9, respectively). Collyer (1973) does not provide a range for the lengths and widths of these two species, and the single measurements provided are assumed to represent the holotype in each case. The delimiting marker points for our length and width measurements are the setae v2–h1 and sc2–sc2, and although the exact delimiting points for body measurements were not described by Collyer (1973), based on the first description in her paper, the length was the full body including gnathosoma and the width was taken at the widest point on the specimen. With this in mind, a difference between the two sets of measurements would be expected, and our measurements would be expected to be lower than Collyer’s as ours are based on distances between dorsal setae and not between the limits of body margins on flattened specimens. Our measurements are 54–64 shorter in length (=18–28%) and 10–20 shorter in width (=6–12%) than the original description for A. alpinus females, and 30–40 shorter in length (=8–11%) and 26 shorter in width (=12%) for female A. montanus. As a comparison, Beard et al. (in press) found that body measurements from older specimens mounted in PVA were approximately 14% shorter and 10% narrower than those from fresh specimens mounted in Hoyer’s medium.

Female — Anterior margin of prodorsum with a short median forked projection forming a shallow notch. Prodorsum with oblique to transverse striations; prodorsal setae v2 and sc1 minute; sc2 short lanceolate, thick; palpi four segmented, with setal formula 0, 0, 2, 2. Central region of opisthosoma with series of transverse striations and lateral region with few longitudinal striations; setae c1 absent; setae c3, d1, d3, e1 and e3 minute; setae f2, f3, and h1 short lanceolate, thick; h2 elongate and filiform. Ventral integument completely striated; setae 1a, 4a1, 4a2 elongate, filiform; two pairs of 4a setae; setae g1 inserted marginally anterior to g2 on membranous genital flap; setae ag, g1–g2 and ps2–ps3 smooth. Leg chaetotaxy (legs I–IV): femora 4-4-2-1, genua 2-2-1-0, tibiae 5-5-3-3, tarsi 8(1)-8(1)-5-5. Body 1.7–1.9 X longer than wide.

Paratypes — 1 female collected on Pimelea sericeo-villosa Hook. (Thymelaeaceae), with litter and soil from beneath this shrub, Mount Grey, 1250m elevation, Turret Range, Lake Manapouri area, New Zealand, 09.i.1970, coll. A.C.E. (NMNH); 1 female collected on seepage sward of Astelia linearis (Astelieaceae), Dracophyllum (Epacridaceae), Forstera (Stylidiaceae), Phyllachne (Stylidiaceae), Mt Barber, 1100m, Wilmot Pass, West of Lake Manapouri, New Zealand, 8.i.1970, coll. J.S.D. and J.M.H (BMNH).

Remarks — The details of the collection data as written on the paratype slide deposited in the NMNH are different to what was presented by Collyer in the original description.

Body measurements — distance between setae v2–h1 330–360, sc2–sc2 190; other measurements: v2–v2 40–42, sc1–sc1 90–92, c3–c3 185–195, d1–d1 47–48, d3–d3 160–165, e1–e1 18–20, e3–e3 150–160, f2–f2 140–150, f3–f3 125–130, h1–h1 63–70, h2–h2 100.

Dorsum (Figures 1A, 2) — Anterior margin of prodorsum with short median forked projection forming a shallow notch. Prodorsum with oblique striations; prodorsal setae v2 and sc1 minute, and sc2 short, thick lanceolate and barbed. Central region of opisthosoma with transverse striations and lateral region with few longitudinal striations; setae c1 absent; c3, d1, d3, e1 and e3 minute; setae f2, f3, and h1 short, thick lanceolate and barbed; h2 elongate and filiform. Setal lengths: v2 4, sc1 4–5, sc2 20–23, c3 3–4, d1 4–5, d3 3–4, e1 4, e3 4–5, f2 15–17, f3 19–21, h1 12–13, h2 100–105.

Venter (Figure 1B). Ventral integument mostly with fine transverse striations; setae 1a, 4a1, 4a2 elongate and filiform; two pairs of setae 4a; setae g1 inserted marginally anterior to g2 on membranous genital flap; setae ag, g1–g2 and ps2–ps3 smooth; other ventral setae fine and smooth. Setal lengths: 1a 120–135, 1b 9–10, 1c 10–12, 2b 12–14, 2c 10, 3a 9–11, 3b 12–14, 4a1 85–95, 4a2 90–105, 4b 11–13, ag 15–17, g1 16–17, g2 18–20, ps2 12–13, ps3 11–12.

Gnathosoma (Figure 3) — Palpi four segmented, setae formula: 0, 0, 2, 2; tibia with two setae, d′ 6, d″ 6, tarsus with two eupathidia, 4–5, 5. Ventral setae m 6; distance between setae m–m 14–15.

Legs (Figure 4) — Chaetotaxy (from coxae to tarsi): I 2-1-4-2-5-8(1), II 2-1-4-2-5-8(1), III 1-2-2-1-3-5, IV 1-1-2-0-3-5. Tarsus I–II each with one abaxial solenidion ω″ 7 and 6, respectivelly, and two eupathidia, pζ′–pζ″ (tarsi I 7, 7; tarsi II 6, 6).

Male — Unknown.

Remarks — According to Collyer (1973), this species was also collected on moss, Celmisia (Asteraceae), Senecio (Asteraceae), Gaultheria (Ericaceae), Coprosma (Rubiaceae), Haastia sinclarii (Asteraceae), grasses (Poaceae) in New Zealand. This collection data suggests that the true host association(s) are unknown.

Female — Anterior margin of prodorsum with a short median forked projection forming a shallow notch. Prodorsum mostly smooth, with weak transverse striations posteriorly; prodorsal setae v2, sc1 minute, smooth; setae sc2 short, smooth, acicular; palps four segmented; central opisthosoma between setae d1 and e1 with few weak transverse striations, lateral opisthosoma with few weak longitudinal striations; dorsal opisthosomal setae short to minute, except setae h2 elongate and filiform. Ventral integument mostly with fine transverse striations; setae 1a, 4a1, 4a2 elongate, filiform; setae g1 inserted marginally anterior to g2 on membranous genital flap; setae ag, g1–g2 and ps2–ps3 smooth. Leg chaetotaxy (legs I–IV): femora 4-4-2-1, genua 2-2-1-0, tibiae 5-5-3-3, tarsi 8(1)-8(1)-5-5. Body 1.8–1.9 X longer than wide. Male: Dorsal integument and setae like those of female; tarsi I–II each with two solenidia; tarsi III–IV with one solenidia.

Type material examined — Paratypes: 1 female and 1 male collected from mixed sample of mat plants on rocks, Mount Robert Ridge circa 1830 m elevation, Nelson Lakes National Park, New Zealand; October 1969, coll. G.W.R. (NMNH); 1 female same data (BMNH).

Body measurements — Distance between setae v2–h1 290–300, sc2–sc2 150–160; other measurements: v2–v2 32–33, sc1–sc1 74–78, c3–c3 135–150, d3–d3 125–145, e1–e1 22–25, e3–e3 100–105, f2–f2 102–105, f3–f3 86–87, h1–h1 30–36, h2–h2 67–70.

Dorsum (Figures 5A, 6) — Anterior margin of prodorsum with short median forked projection forming a shallow notch. Prodorsum mostly smooth with weak transverse striations posteriorly; prodorsal setae v2, sc1 minute; setae sc2 short, smooth; central opisthosoma between setae d1 and e1 with weak transverse striations; lateral opisthosoma with few weak longitudinal striations; dorsal opisthosomal setae short to minute, except setae h2 elongate, filiform. Setal lengths: v2 3–4, sc1 4–5, sc2 7, c3 4, d1 3–4, d3 3–4, e1 4, e3 3–4, f2 5, f3 5, h1 6–7, h2 65–70.

Venter (Figure 7A) — Ventral integument with fine transverse striations; setae 1a, 4a1, 4a2 elongate, filiform; two pairs of setae 4a; setae g1 inserted marginally anterior to g2 on membranous genital flap; setae ag, g1–g2 and ps2–ps3 smooth; other ventral setae fine and smooth. Setal lengths: 1a 85–105, 1b 9–11, 1c 9–10, 2b 11–12, 2c 10–14, 3a 10–12, 3b 11–12, 4a2 30–43, 4a2 35–50, 4b 8–10, ag 7–8, g1 8–9, g2 7–8, ps2 11–12, ps3 10–11.

Gnathosoma (Figure 7B) — Palpi four segmented, setae formula: 0, 0, 2, 2; tibia with two setae, d′ 5, d″ 5, tarsus with two eupathidia 3, 2. Ventral setae m 6–7; distance between setae m–m 12–13.

Legs (Figure 8) — Chaetotaxy (from coxae to tarsi): I 2-1-4-2-5-8(1), II 2-1-4-2-5-8(1), III 1-2-2-1-3-5, IV 1-1-2-0-3-5. Tarsi I–II each with one abaxial solenidion ω″ 8 and 7, respectivelly, and two eupathidia distally pζ′–pζ″ (7, 7 for both tarsi).

Body measurements — Distance between setae v2–h1 230, sc2–sc2 125; other measurements: v2–v2 32, sc1–sc1 65, c3–c3 100, d1–d1 33, d3–d3 90, e1–e1 20, e3–e3 68, f2–f2 65, f3–f3 55, h1–h1 30, h2–h2 50.

Dorsum (Figure 5B) — Dorsal integument and setae similar to those of female. Setal lengths: v2 4, sc1 3, sc2 7, c3 4, d1 3, d3 3, e1 3, e3 3, f2 4, f3 5, h1 5, h2 55.Venter. Ventral integument and setae similar to those of female; setae 1a, 4a1, 4a2 elongate and filiform. Setal lengths: 1a 100, 1b 6, 1c 8, 2b 8, 2c 7, 3a 13, 3b 11, 4a1 38, 4a2 40, 4b 8, ag 7, g113, g2 13, ps2 8, ps3 6.

Gnathosoma — Similar to that of female; tibia with two setae, d′ 5, d″ 6, tarsus with two eupathidia 3, 2. Ventral setae m 4; distance between setae m–m 13.

Legs (Figure 9) — Chaetotaxy (from coxae to tarsi): I 2-1-4-2-5-9(2), II 2-1-4-2-5-9(2), III 1-2-2-1-3-6(1), IV 1-1-1-0-3-6(1). Setae d, l′, l″ on femora, genu and tibia I–II slightly thickened, weakly barbed. Tarsi I–II each with two solenidion (one abaxial, one adaxial), tarsi I ω′ 7, ω″ 7, tarsi II ω′ 7, ω″ 7, and two eupathidia pζ′–pζ″ (all 6–7); tarsus III–IV each with one abaxial solenidion, tarsi III 6, tarsi IV 7.

According to Collyer (1973), this species was also collected from mixed mats of plants including: Chionochloa crassiuscula (Poaceae), Astelia, Celmisia sessiliflora (Asteraceae), Cyathodes pumila (Epacridaceae), Gaultheria, Anisotome (Apiaceae) and Drosera (Droseraceae) in New Zealand. This collection data suggests that the true host association(s) are unknown.

All previously known species of Acaricis were collected on plants of the family Cyperaceae; whereas A. montanus and A. alpinus were collected in association with many species and families of alpine heath plants, none of which were identified as Cyperaceae (Collyer 1973). In discussing A. montanus and A. alpinus, Collyer (1973) states herself that there “can be no certainty of their host plant relationships” as the specimens were collected from samples of mixed plants. Despite the apparent difference in host relationships, A. montanus and A. alpinus both share with other Acaricis species: anterior margin of prodorsum with median forked process, two pairs of ventral setae 4a; dorsal setae c1 is absent; the palps are four segmented with setae formula 0, 0, 2, 2; genital setae g1 are inserted (marginally) anterior to g2; setae ft′ are suppressed on tarsus I–II and ft″ suppressed on tarsi III–IV; setae ft″ are filiform on tarsi I–II; and the males have two solenidia on tarsi I–II. Acaricis alpinus males also share one solenidion on tarsus III–IV with A. plana and A. urigersoni (male not known for A. montanus; A. danutae males without solenidion on tarsus III–IV). Additional solenidia on tarsus III are also commonly seen in species of Tenuipalpus sensu stricto, but are not commonly seen on tarsus IV (Castro et al. 2015). Acaricis montanus and A. alpinus differ to all other Acaricis in having a seta on trochanter IV, while the other three known species have a nude trochanter IV. The other New Zealand species, A. urigersoni, is the only Acaricis to have prodorsal setae v2 absent, it also has different chaetotaxy on leg IV to all other species in the genus, with only one seta on femur IV (seta d present, ev′ absent), only two setae on tibiae IV (v′, v″ present; d absent); and genua III–IV are nude (only genua IV nude in other Acaricis species). All three New Zealand species also share a short median forked process on the anterior margin of the prodorsum, which is much longer in the two Australian species.

1. Prodorsal setae v2 absent; prodorsal setae sc1 minute, bifurcate; dorsal opisthosomal setae e3 lanceolate; femora IV with one seta (d present; ev′ absent); genua III–IV nude; tibiae IV with two setae (v′, v″ present; d absent
...... A. urigersoni Xu & Zhang

— Prodorsal setae v2 present; prodorsal setae sc1 acicular; dorsal opisthosomal setae e3 minute, acicular or barbed; femora IV with two setae (d, ev′ present); genua III with one seta (d present), genua IV nude; tibiae IV with three setae (d, v′, v″ present)
...... 2

2. Body elongate, more than twice as long as wide; median forked projection on anterior margin of prodorsum long with deep notch; genital setae g1 inserted well anterior to g2
...... 3

— Body almost twice as long as wide (1.7–1.9 X longer than wide); median forked projection on anterior margin of prodorsum short with shallow notch; genital setae g1 inserted marginally anterior to g2
...... 4

3. Dorsal opisthosomal setae e3 minute, fine; prodorsal setae sc2 lanceolate, stout; dorsal seta d on femur III lanceolate, thickened
...... A. plana Beard & Gerson

— Dorsal opisthosomal setae e3 short, thickened, barbed; prodorsal setae sc2 short, barbed; dorsal seta d on femur III short, fine
...... A. danutae Beard & Gerson

4. Prodorsal setae sc2 lanceolate, stout (20–23 μm) and distinctly longer than setae v2 and sc1 (both minute; 4–5 μm)
...... A. montanus (Collyer)

— Prodorsal setae sc2 acicular, short, fine (7 μm) and slightly longer than v2 and sc1 (both minute; 3–5 μm)
...... A. alpinus (Collyer)

To Debra Creel and Andrew Ulsamer (SEL-USDA) for their help with references and technical support. To the Smithsonian Natural History Museum and National Agricultural Library (NAL-USDA), SEL-USDA for support and assistance with specimens and references. We thank Dr Janet Beccaloni, British Museum of Natural History (BMNH) for lending the types. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA; USDA is an equal opportunity provider and employer. This work was supported by the "Fundação de Amparo à Pesquisa do Estado de São Paulo" (FAPESP) (Procs. 2016/01193-5 and 2017/00458-8) through a fellowship to the first author; by a research grant from the Australian Biological Resources Study, Department of Environment and Energy, Australian Government [grant RF214-23] to the second author; and by a research grant from the "Conselho Nacional de Desenvolvimento Científico e Tecnológico" (CNPq) (Proc. 303435/2013-5) to the fourth author.

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