Review of Amblyseius Berlese (Acari: Phytoseiidae) in Western Siberia, Russia

Mites of the genus Amblyseius (Acari: Phytoseiidae) in Western Siberia, Russia are reviewed. Amblyseius silvaticus (Chant), A. ampullosus Wu and Lan and A. myrtilli Papadoulis, Emmanouel and Kapaxidi are recorded for the first time from Russia. Females of A. silvaticus, A. omaloensis, A.myrtilli and A. ampullosus are redescribed in detail and males of A. silvaticus and A. ampullosus are described for the first time. Chaetotaxy of tarsus I for all studied species is presented. Moreover, the importance of apical sensorial setal cluster of tarsus I in identification of phytoseiid mites is discussed.


Introduction
Phytoseiid mites are important natural enemies of phytophagous mites and other different small arthropods. Some of them, such as Phytoseiulus persimilis (Athias-Henriot), Amblyseius swirskii (Athias-Henriot), Transeius montdorensis (Schicha), Neoseiulus californicus (McGregor) are available commercially for use in greenhouses. Phytoseiid mites are widely distributed around the world and presently include more than 2,500 valid species in three subfamilies and 94 genera (Demite et al. 2020;Chant and McMurtry 2007). The genus Amblyseius is the largest in the subfamily Amblyseiinae, with 434 nominal species (Demite et al. 2020).

Materials and methods
The mites were collected directly from plant leaves using stereomicroscope Discovery V8 and placed in vials filled with 96% ethanol. Mites from bark and soil samples were extracted using Berlese-Tullgren funnels. Specimens were cleared in lactic acid solution and mounted in Hoyer's medium (Walter and Krantz 2009).
Systematics of Phytoseiidae follows that of Chant and McMurtry (2007). Setal nomenclature for the dorsal idiosoma follows that of Lindquist and Evans (1965) as adapted by Rowell et al. (1978), and Chant and Yoshida-Shaul (1991) for ventral idiosoma. The chaetotaxy of the palp tibia and tarsus and the distal part of tarsus I follows that of Jackson (1974). Chaetotaxy of other parts of legs and palps follows that of Evans (1963Evans ( , 1964Evans ( , 1969. For designation of dorsal solenostomes and poroids, nomenclature proposed by Athias-Henriot (1975) and Johnston and Moraza (1991) for ventral surface of idiosoma was used. Terminology of the morphological structures of spermatodactyl follows that of Beard (2001). World distribution of investigated species is based on Demite et al. (2020). Measurements of morphological structure are given in micrometers (µm) and presented as a mean followed by the range in parenthesis. Morphological observations, illustrations and measurements were made using compound microscope Axio Imager A2 (Carl Zeiss, Germany), equipped with differential interference contrast (DIC) and phase contrast optical system. Pictures were taken with Axiocam 506 color (Carl Zeiss, Germany). Dorsal shield length measured along the midline from j1 setae level to J5 setae level; dorsal shield width taken at R1 setae level. Length and width of sternal shield were measured as distance between bases of setae ST1-ST3 and ST2-ST2 for females and distance between bases of setae ST1-ST5, ST2-ST2 for males, respectively. Length of legs is from basis of the coxa to apex of the tarsus, excluding pre-tarsus.
The following abbreviations are used in this paper for morphological characters: Dsldorsal shield length; Dsw -dorsal shield width; Vsl -ventrianal shield length; Vsw ZV2ventrianal shield width at ZV2 setae level; Nbf -number of teeth on the fixed digit; Nbmnumber of teeth on the movable digit.
All examined materials are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.
Measurements of macrosetae as follows: SgeII 30 (  Remarks -Amblyseius ampullosus is very similar to A. verginensis Papadoulis, 1995, but differs in atrium shape of spermatheca, slightly bulbous and C-shaped in A. verginensis (vs. well sclerotized and nodular-like in A. ampullosus) ( Figure 10E). This species was originally described from China, mountain He-Lan-Shan, on Artemisia sp. (Wu and Lan, 1991). It was also recorded and redescribed from Iran, from soil (Shirdel et al., 2009), and this is the first record from Russia.
My newly collected material agree very well with the original description given by Wu and Lan (1991).
Remarks -This species was originally described from Nakusp, British Columbia, Canada, on Ranunculus sp. as T. (Amblyseius) berlesei (Chant 1957). In 1959, this species was renamed to A. krantzi (Chant 1959). In Russia, this species was previously recorded from the Moscow (Meshkov 1999) and Yaroslavl provinces (Wainstein 1975). This species is recorded for the first time in Asian Russia. The characteristics of the specimens herein considered agree well with those of the descriptions given by Chant and Hunsell (1971), Congdon (2002) and Kolodochka and Gwiazdowicz (2016). However, the number of teeth on the movable digit in the material here observed is a variable character as some females had two teeth instead of three in the original description and further redescriptions. This species is common on grassy plants in dark spruce forests or in mixed forests with a predominance of spruce. It could be often found together with Amblyseius rademacheri Dosse (personal observation).
Remarks -This species was originally described from Potenza, Basilicata, Italy, in humus (Berlese 1914). It is known from 21 countries in the Palearctic and Nearctic regions (Moraes et al. 2004;Demite et al. 2020). It was previously recorded from leaves of Poterium polygamum (Rosaceae) in Crimea, Russia by Livshitz and Kuznetsov (1972). Siberian specimens well agree with redescription given by Faraji et al. (2011). This species is recorded for the first time in Asian Russia.
Remarks -All measurements and morphological characters of Siberian specimens are very close to those of the redescription of Kolodochka and Gwiazdowicz (2016). This species is the most abundant in the investigated area. It is common on various grassy plants and often found with another species of Phytoseiidae mites in the present survey.
Remarks -Amblyseius obtusus is a cosmopolitan species, reported in more than 30 countries (Demite et al., 2020). All measurements and morphological characters of Siberian specimens are very close to redescription of Döker et al. (2020). It is a first record of A. obtusus in Asian Russia.
Remarks -Amblyseius omaloensis is known only from Europe (Demite et al., 2020). All measurements and morphological characters of Siberian specimens are very close to description of Meshkov (1991). It is the first record of A. omaloensis in Asian Russia.
Remarks -Amblyseius myrtilli is known only from Greece, on leaves of Vaccinium myrtillis (Ericaceae) and from litter under Juniperus sp. Morphological characteristics of Siberian specimens are consistent with those provided in the original description (Papadoulis et al., 2009). It is the second record of A. myrtilli in the world and the first report in Russia. The record of A. myrtilli in Russia is not accidental, since in Greece it was found in the mountains at an altitude of 1800 m. At this altitude, the climate is moderate and more or less similar to the southwestern Siberia.

Discussion
Usually, Phytoseiidae taxonomists, pay little attention to leg chaetotaxy and only report the length of macrosetae and chaetotaxy formula of genua II and III. The chaetotaxy of tarsus I is not considered, and the utility of some characters in Phytoseiidae species identifications is discussed below. Jackson (1974)  I in detail, based on specimens of Phytoseiulus persimilis. On the distal part of tarsus I, he recognized nine group of short, peg-or spur-like setae and designated them by the prefix as df (''dorsal field''). In all the Siberian Amblyseius specimens here considered, I identified on the distal part of tarsus I the group of ten modified, different in shape setae df1-df10 (Figs. 6C,6D,26,27). Nine of them (df1-df9) are similar in shape and situated on the same positions as described for P. persimilis (Jackson 1974). However, I examined an additional seta in this complex, designated here as df10. This seta is similar in shape to setae df4 and df9 (spur-like), but shorter in length and always situated between them. Moreover, I discovered some differences in apical sensorial setal cluster between the Amblyseius species here considered. The most noticeable differences in the length of setae df6. For example, in A. silvaticus, A. rademacheri and A. krantzi this setae 12-13 in length vs 16-17 in other species (Figs. 26,27). Also, the shape of setae df1 usually thickened finger-shaped in most Siberian Amblyseius species, except narrow baculiform in A. krantzi and A. rademacheri (Figs. 26C, 27A).
All characters discussed above, are stable and were measured on several specimens of each Amblyseius species. In my opinion, tarsus I of phytoseiid mites is an important segment for identification on generic (at least Phytoseiulus and Amblyseius) and species levels and should be carefully studied in different Phytoseiidae genera. The use of sensory setae on tarsus I as diagnostic character is very limited in other groups of Mesostigmata. The best example is description of tarsal sensory cluster in some genera of Blattisocidae (Phytoseioidea) (Lindquist, Moraza 2010, 2012Moraza, and Lindquist 2011). Leonovich (1989) provided the detailed morphological structure of setal structures in tarsal sensory complex and revealed the difference in its structure in different families of Gamasina. The correct study of all setae in tarsal sensory cluster requires high quality microscopes with DIC illumination as well as SEM microscopes; Table 4 Character measurements of adult females of Amblyseius myrtilli collected in this study compared to previously published character measurements of adult females of A. myrtilli (localities followed by the number of specimens measured between brackets). A B 10 !lill d3 c D Figure 26 Apical sensorial setal cluster area and setae d3 and d4 of tarsus I, female, right leg, dorsal aspect: A -Amblyseius silvaticus Chant, 1959; B -Amblyseius ampullosus Lan, 1991, C -Amblyseius krantzi Chant, 1959, D -Amblyseius meridionalis Berlese, 1914. however, the most obvious diagnostic character (ratio of length of setae d3 and d4) is clearly discernable in phase contrast and even in bright field.
The chaetotaxy of palps and tarsus I are similar in the male and female for all studied species.
I studied tarsal sensory cluster only for abovementioned species of the genus Amblyseius. In the next papers on the systematics of Siberian Phytoseiidae, I am going to described tarsal sensory clusters in other specious genera, such as Transeius, Neoseiulus and Typhlodromus.