Naiadacarus, Fashing, 1974

Klimov, Pavel B., Oconnor, Barry & Khaustov, Alexander A., 2019, Naiadacarus sidorchukae sp. n. (Acariformes: Acaridae) from Western Siberia closely related to a North American species, with a new generic synonymy, Zootaxa 4647 (1), pp. 441-456 : 451-452

Key to species of the genus Naiadacarus of the world

Phoretic deutonymphs*

1. Gnathosoma distinctly expanded at base. Solenidion ω 2 on tarsus I absent. Genual seta nG III present. Conoids ps 1 and ps 2 arranged in a very shallow, inverted arch; anterior transverse level of ps 2 posterior to posterior level of median suckers (ad 1+2). Prodorsum unscuptured, smooth. Brunei Darussalam. Inhabits fluid-filled pitcher of plant Nepenthes bicalcarata . Deutonymphs phoretic on ants Camponotus schmitzi nesting exclusively in hollow tendrils of the plant pitchers.......................................................................................... N. nepenthicola Fashing and Chua, 2002

- Gnathosoma nearly parallel-sided. Solenidion ω 2 on tarsus I present. Genual seta nG III absent. Conoids ps 1 and ps 2 arranged in a semicircular, inverted arch; anterior transverse level of ps 2 anterior to posterior level of median suckers (ad 1+2). Prodorsum sculptured (weakly in N. muertensis )...................................................................... 2

2(1) Coxal setae 1a and 3a in form of rounded conoids. Scapular setae se situated outside prodorsal shield. Tarsi III–IV short, nearly 3 times long as their height at base. Costa Rica. Host unknown, found in bromeliad leaf axils together with feeding stages............................................................................... N. muertensis ( Nesbitt, 1990)

- Coxal setae 1a and 3a filiform. Scapular setae se situated on prodorsal shield. Prodorsum and hysteronotum uniformly sculptured. Tarsi III–IV longer, more than 3 times longer of their height at base........................................ 3

3(2). Dorsal ornamentation with irregular protuberances separated by sinuous grooves. Coxal setae 4a with expanded bases and filiform tips. Setae kT of tibia IV and w of tarsus IV smooth. USA (Arkansas, Kansas, Michigan, Missouri, Minnesota, New York, Pennsylvania, Virginia). Inhabits water-filled tree holes. Deutonymphs typically phoretic on species of syrphid fly genus Mallota , whose larvae develop in the same habitat..................................... N. arboricola Fashing, 1974

- Dorsal ornamentation with dense punctations. Coxal setae 4a either filiform ( N. mydophilus ) or in form of rounded conoids ( N. fashingi , N. sidorchukae ). Setae kT of tibia IV and w of tarsus IV distinctly barbed.................................. 3

4(3). Palpal supracoxal setae (elc p) on gnathosomal remnant present. Coxal setae 4a filiform. USA (Michigan). Phoretic on syrphid fly, Brachypalpus oarus ........................................................ N. mydophilus OConnor, 1989

- Palpal supracoxal setae (elc p) on gnathosomal remnant absent. Coxal setae 4a in form of rounded conoids.............. 4

5(4). Tibial solenidion φ II longer, 35–49 (42±4, n=23), as long as tarsus II; ratio tibial solenidion φ II/tarsus II 0.94–1.17 (1.02±0.05, n=23). USA (Michigan, New York, New Jersey). Phoretic on various syrphid flies, including Brachypalpus oarus (type host).............................................................................. N. fashingi OConnor, 1989

- Tibial solenidion φ II shorter, 20–32 (27±3, n=23), shorter than tarsus II; ratio tibial solenidion φ II/tarsus II: 0.62–0.93 (0.79±0.08, n=23). Russia (Western Siberia). Phoretic on Ips typographus ....................... N. sidorchukae , sp. n.

Adults*

1. Genual seta nG III present. Most of gnathosoma covered dorsally by propodosoma (camerostome present). Dorsum covered with sclerotized ridges. Dorsal hysterosomal setae robust and larger in basal diameter. Coxal fields I–II completely covered by continuous sclerotization; sclerotization extends dorsally to connect to prodorsal shield. Tarsal setae e I–III distinctly longer than height of corresponding tarsi. Tarsus IV of male inflated; seta r IV lanceolate. Brunei Darussalam. In fluid-filled pitcher of the plant Nepenthes bicalcarata ........................................ N. nepenthicola Fashing and Chua, 2002

- Genual seta nG III absent. Most of gnathosoma not covered dorsally by propodosoma (camerostome absent). Dorsum not covered with sclerotized ridges. Dorsal hysterosomal setae not expanded at bases. Coxal fields I–II not completely covered by continuous sclerotization; sclerotization does not extend dorsally and not connected with prodorsal shield. Tarsal setae e I–III nearly as long as height of corresponding tarsi. Tarsus IV of male regular, not inflated; seta r IV spiniform.............. 2

2(1) Genua I–II each with single seta (gT I–II present, hT I–II absent). Dorsal hysterosomal setae robust and larger in basal diameter. Coxal apodemes III closed. Tarsal setae e I–II distinctly longer than height of corresponding tarsi. Tarsal setae ba I–II subequal (tarsus I) to or longer (tarsus II) than half of corresponding solenidia ω 1. Costa Rica. Water in bromeliad leaf axils..................................................................................... N. muertensis ( Nesbitt, 1990)

- Genua I–II each with two setae (gT I–II and hT I–II present). Coxal apodemes III open. Dorsal hysterosomal setae not robust, not expanded at bases. Tarsal setae e I–II nearly as long as height of corresponding tarsi. Tarsal setae ba I–II shorter than half of corresponding tarsal solenidia ω 1. USA. Water-filled tree holes............................................... 3

3(2). Dorsal idiosomal setae e 1 not reaching level of setae h 1. At least half of area of each coxal fields II–IV covered by sclerotization. In female, posterior dorsal hysterosomal sclerotization absent. In male, posterior dorsal hysterosomal sclerotization does not bear setae; anterior anal sclerite v-shaped; setae ps 2 situated posterior to anterior level of anal suckers (on sides of suckers). USA (Arkansas, Kansas, Michigan, Missouri, Minnesota, New York, Pennsylvania, Virginia). In water-filled tree holes................................................................................. N. arboricola Fashing, 1974

- Dorsal idiosomal setae e 1 extending beyond level of setae h 1. Most of area of each coxal fields II–IV not covered by sclerotization. In female, posterior dorsal hysterosomal sclerotization present. In male, posterior dorsal hysterosomal sclerotization bear setae h 1; anterior anal sclerite crescent-shaped; setae ps 2 situated anterior to anterior level of anal suckers. USA (Oregon). In water-filled tree holes......................................................... N. oregonensis Fashing, 1974

* N. oregonensis (water-filled tree holes, USA: Oregon) is known from adults only ( Fashing, 1974).

N. fashingi , N. sidorchukae , and N. mydophilus are known from deutonymphs only. Two undescribed taxa have been reported in the literature: one is from Austria (water-filled hole in a tree stump, feeding stages only) ( Wurst, 2006) and another is from Guatemala (bromeliad, feeding stages; phoretic deutonymphs were obtained in the lab) ( Okabe & OConnor, 2001).