Scapulaseius asiaticus (Evans)

Kreiter, Serge & Abo-Shnaf, Reham I. A., 2020, New records of phytoseiid mites from Mauritius Island (Acari: Mesostigmata, Acarologia 60 (3), pp. 520-545 : 524-526

Scapulaseius asiaticus (Evans)

Typhlodromus asiaticus Evans 1953: 461 .

Typhlodromus (Amblyseius) asiaticus, Chant 1959: 80 .

Amblyseius (Typhlodromopsis) asiaticus, Muma 1961: 289 .

Amblyseius (Amblyseius) asiaticus, Ehara 1966: 20 ; Ehara & Bhandhufalck 1977: 58.

Amblyseius asiaticus, Carmona 1968: 280 ; Gupta, 1975: 32.

Amblyseius (Neoseiulus) asiaticus, Ehara 2002: 127 .

Typhlodromips asiaticus, Moraes et al. 2004: 207 .

Scapulaseius asiaticus, Chant & McMurtry 2005b: 335, 2007: 67 .

Scapulaseius linearis Corpuz & Rimando 1966: 125 (synonymy according to Schicha & Corpuz-Raros 1992).

Scapulaseius siaki Ehara & Lee 1971: 64 (synonymy according to Ehara & Bhandhufalck 1977).

Species of this genus are supposed to be of type III ( McMurtry and Croft 1997; McMurtry et al. 2013), i.e., a polyphagous generalist predator. However, the biology of S. asiaticus remains totally unknown. This species had been collected before in Mauritius ( Kreiter et al. 2018a; Ferragut and Baumann 2019).

World distribution: Angola, China, Cyprus, Hong Kong, India, Indonesia, Malaysia, Philippines, Singapore, Sri Lanka, Thailand, Vietnam.

Specimens examined: 27 ♀♀ and 5 ♂♂ in total. Côte d’Or, Village (aasl 443 m, lat. 20°15 ′ 26 ″ S, long. 57°32 ′ 21 ″ E), 2 ♀♀ on Clibadium surinamense L. ( Asteraceae ), 28/X/2018; Curepipe, Trou aux cerfs (aasl 593 m, lat. 20°19 ′ 04 ″ S, long. 57°30 ′ 47 ″ E), 1 ♀ on Rubus apetalus Poiret (Rosaceae) , 29/X/2018; Mare aux Vacoas (aasl 572 m, lat. 20°21 ′ 40 ″ S, long. 57°29 ′ 59 ″ E), 11 ♀♀ on Tibouchina heteromalla Cogniaux (Melastomataceae) and 2 ♀♀ on Litsea monopetala (Roxburgh) Person (Lauraceae) , 30/X/2018; Quartier Militaire (aasl 472 m, lat. 20°19 ′ 11 ″ S, long. 57°36 ′ 05 ″ E), 1 ♀ on Clidemia hirta (L.) D. Don ( Melastomataceae ), 1/XI/2018; Curepipe, Bld Pasteur (aasl 510 m, lat. 20°19 ′ 21 ″ S, long. 57°31 ′ 45 ″ E), 1 ♀ on Ageratum conyzoides L. ( Asteraceae ), 4/XI/2018; Curepipe, Anderson street (aasl 560 m, lat. 20°19 ′ 11 ″ S, long. 57°31 ′ 52 ″ E), 5 ♀♀ and 3 ♂♂ on Erigeron canadensis (L.) Cronquist ( Asteraceae ) and 3 ♀♀ and 2 ♂♂ on Sonchus oleraceus L. ( Asteraceae ), 4/XI/2018; Mare aux Vacoas (aasl 581 m, lat. 20°22 ′ 05 ″ S, long. 57°29 ′ 31 ″ E), 1 ♀♀ on Ludwigia octovalvis (Jacquemin) P.H.Raven (Onagraceae) , 5/XI/2018.

Remarks: Scapulaseius asiaticus was described by Evans (1953) under the name Typhlodromus asiaticus from specimens collected in Java island, Indonesia. The closely related Scapulaseius reptans (Blommers) was described by Blommers in 1974 from Madagascar in Tamatave from specimens collected on Psidium guajava L.

Character measurements of 12 of the 27 females ( Table 1) and of the five males ( Table 2) collected in Mauritius agree very well with those obtained from specimens of S. asiaticus or S. reptans . We consider so far that our specimens can be anyone of the two species and that examination of the specimens collected in this study can lead to anyone of the two species. Consequently, the morphometrics strongly suggest synonymy.

There are however some discrepancies between our measurements and observations and previous descriptions of the two species. In the two descriptions:

• dorsal shield is reticulated in the description S of. reptans in the anterior lateral margins and on all the posterior part of the dorsal shield except the centre. This was not illustrated in the original description of S. asiaticus by Evans (1953), but was illustrated by Ehara and Bhandhulfalck (1977) and by Ferragut and Baumann (2019);

• Ehara and Bhandhulfalck (1977) pointed out that the seta R1 is inserted on a lateral projection of the dorsal shield, trait taken back also by Ferragut and Baumann (2019). Scapulaseius reptans is morphologically very close to S. asiaticus , but with setae R1 located off the dorsal shield in the description of Blommers (1974). Taking this trait into consideration as an apomorphic character, Chant and McMurtry (2005c) placed the two species within different groups, S. asiaticus in the asiaticus species group characterized by having R1 on the dorsal shield and S. reptans in the ficilocus species group with species bearing R1 on the lateral integument. However, in S. asiaticus the position of this seta is variable even among individuals of the same population. Ehara and Bhandhufalck (1977) were the first to mention this variability. Ferragut and Baumann (2019) had examined 19 females from Mauritius: eleven females (58%) have both R1 setae on the dorsal shield, four females (26%) have one setae of the pair on a lateral projection of the shield and the other on the soft integument, and three females (16%) have both setae R1 on the lateral integument. If the majority of specimens have both or one seta on the dorsal shield, 16% is not a negligible proportion;

• a peculiar trait in S. asiaticus not mentioned by previous authors and especially by Blommers (1974) for S. reptans is the position of the dorsal solenostome gd3. Ferragut and Baumann (2019) stated that while in females of the family Phytoseiidae , this pore-like structure is usually placed on the peritremal plate, in S. asiaticus , it is on the lateral integument, between the peritremal and dorsal shields, posterior to setae r3 and close to the margin of dorsal shield.

Our examination of the material collected in Mauritius (this study) and Vietnam ( Kreiter et al 2020b) and identified as S. asiaticus and of the material collected in Mauritius ( Kreiter et al. 2018a) and in La Réunion ( Kreiter et al. 2020c) and identified as S. reptans along with the original descriptions of S. asiaticus and S. reptans shows:

• Re-examination of our specimens from La Réunion ( Kreiter et al. 2020c) and of Mauritius ( Kreiter et al. 2018a) show that the dorsal shields of the two species present exactly the same reticulation as drawn by Bommers (1974) for the description of S. reptans and in Ehara and Bhandhulfalck (1977) for the redescription of S. asiaticus ;

• In our 27 specimens females of Mauritius (this study), we have 21 females out of 27 (77.8%) with R1 on the dorsal shield, four females / 27 (14.8%) with one of these setae on and the other one off shield and two females / 27 (7.4%) with setae R1 both off shield, compared to 58, 26 and 16% for Ferragut and Baumann (2019), respectively. In specimens from Vietnam ( Kreiter et al. 2020b), we had four females out of seven (57.1%) with R1 on the dorsal shield, only one female / seven (14.3%) with one of these setae on and the other one off shield and two females / seven (28.6%) with setae R1 both off shield. In the two specimens from Maurice ( Kreiter et al. 2018a), both specimens have R1 on the dorsal shield. And in the two female specimens from La Réunion ( Kreiter et al. 2020c), one specimen has both R1 on the dorsal shield, but the other specimens have one seta on and the other one off the dorsal shield.

• solenostomes gv3 are on integument in all our specimens from Mauritius (this study), from Vietnam ( Kreiter et al. 2020b), but also on those from Mauritius ( Kreiter et al. 2018a) and La Réunion ( Kreiter et al. 2020c) previously identified as S. reptans .

Given this variability in S. asiaticus , we agree with Ferragut and Baumann (2019) that the taxonomic status of S. reptans is uncertain, because the holotype used to describe the latter species could represent, in fact, a female of S. asiaticus with setae R1 outside their most common position. Setal measurements and other morphological features of the specimens collected in Mauritius agree well with both, with those of the original description and subsequent redescriptions of S. asiaticus by Ehara and Bhandhufalck (1977), Moraes et al. (2004), Oliveira et al. (2012), Karmakar and Bhowmik (2018) and Ferragut and Baumann (2019); as well as with the morphological data provided in the original description S. of reptans , and the redescriptions given by Kreiter et al. (2018a, 2020c).

Considering all this information, we can conclude that our specimens from Mauritius (this study and Kreiter et al. 2018a) and from La Réunion ( Kreiter et al. 2020c) must be all identified as S. asiaticus . Previous specimens collected in La Réunion Island ( Kreiter et al. 2020c) and in Mauritius Island ( Kreiter et al. 2018a) and previously identified as S. reptans are consequently belonging all to S. asiaticus . Consequently, this is the third report of that species in Mauritius Island after Kreiter et al. (2018a) and Ferragut and Baumann (2019).

Unfortunately, the confinement during the Covid-19 pandemic has not given us the possibility to borrow type materials of both species in order to compare specimens of the two species. Despite this fact, we strongly suspect just like Ferragut and Baumann (2019) that S. reptans is a junior synonym of S. asiaticus .