Two species of Acaricis (Acari: Tenuipalpidae) from New Zealand, moved from the genus Tenuipalpus, with a key to the known species

Acaricis Beard and Gerson (Acari: Tenuipalpidae) is a small genus of flat mites with three species described from Australian and New Zealand sedges (Poales: Cyperaceae). In this article, we redescribe two species, Tenuipalpus montanus Collyer and T. alpinus Collyer, and move them to the genus Acaricis, so that these species become Acaricis montanus (Collyer) comb. nov. and A. alpinus (Collyer) comb. nov.. These two species share several characters with other Acaricis that species of Tenuipalpus do not. A key to the world species of Acaricis is also proposed.


Materials and methods
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.

Remarks
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.
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.

Discussion
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.