Review of The Diversity of Macrochelid Mites from Sumatra, Indonesia

Macrochelidae is known as one of the acarine biocontrol agents which target agricultural pests. In this article, we conducted a literature review of the species of Macrochelidae (Acari: Mesostigmata) in Sumatra, Indonesia. The association between Macrochelid mite and insects and their potential use are also discussed. Most of the Macrochelid mites were collected from the surface body of dung beetles Scarabaeidae, captured by baited pitfall trap (human dung trap). Twenty-two species of Macrochelidae belonging to 5 genera are found in Sumatra. None of them is endemic, and there have been no reports of the use of Macrochelid for the agricultural system on this island so far. Therefore, intensive research on Macrochelidae on Sumatra Island is needed.


Introduction
Macrochelid mite belongs to the family Macrochelidae under Phylum Arthropoda, Class Arachnida, Subclass Acari, and order Mesostigmata.The body size of this mite ranges between 300-1200 μm.Most macrochelid mites are free-living in soil, beachside debris, poultry manure, leaf litter, dung, and decomposing animals and many species are phoretic on other animals.They have also been collected from the nest of small mammals, birds, and social insects [1,2].Macrochelid mite plays a significant role as a predator of nematodes, oligochaetes, larvae, and eggs of flies and other arthropods [2].
There are some special characteristics of Macrochelidae, i. e: dorsal shield with lines and punctures ornamentation, 27-31 pairs of dorsal setae, and well-developed tritosternum.Three pairs of setae and two pairs of pores on the sternal shield, ventrianal or anal shield present; peritremes present on the lateral side of the body, hook-shaped and joining to stigma at the end.Well-developed corniculi present on the gnathosoma, tripartite tectum (unipartite on some species); chelicerae bearing 1-2 arthrodial processes on the base of the movable digit.First tarsi without claws; two anterolateral setae on the tibia and genu I; 6-8 setae on the genu IV [1].
Sumatra is one of the largest islands in Indonesia.Research on macrochelid mites on this island had been started by Oudemans in 1903, then continued by Berlese, Vitzthum, and Krantz [3][4][5][6][7][8][9][10][11].After that, serial studies on macrochelids mites associated with dung beetles have been done by some researchers mainly by Takaku and Hartini from early 1990 to 2015 [12,13].This research aims to study the diversity of Macrochelid mites, their association with insects (dung beetles), and the potential use of this mite in Sumatra, Indonesia based on a literature study.

Methods
A literature review was conducted in this research.Most of the reviewed papers stated that macrochelid mites in Sumatra were collected from the surface body of Scarabaeidae.Scarabaeidae was captured in the field using dung traps or directly hand-picked from dung or cattle in pasture [1].Mites were also collected from dried specimens of Scarabaeid beetles in the Museum Zoologicum Bogoriense (MZB) [1].One species was collected from the bird's nest and one species from Polyporus [7].
Identification of Macrochelid mites was mainly based on the morphology features of the females.The dorsal shield chaetotaxy and sternal shield ornamentation were used to diagnose and determine species.

Diversity of Macrochelidae in Sumatra
Twenty-two species of Macrochelid mites were found in Sumatra, Indonesia.They belonged to 5 genera, i.e.: Geholaspis, Glyptholaspis, Holostaspella, Macroheles, and Neopodocinum (Table 1).Only one species of Geholaspis was recorded from Indonesia, i.e.: G. subspinosus.This genus was widely distributed in Europe and reported from New Zealand [19].The presence of G. subspinosus in Indonesia is still doubtful because of inadequate information about this species [1,20].There were no drawing figures and undesignated type depository for this species.
One species of Glyptholaspis, G. asperrima, was reported.The body of this genus is usually bigger than other genera, more than 1000 μm, and shows strong ornamentation at both dorsal and sternal shields.Dorsal shield of the female of G. asperrima bears 28 pairs of setae and is ornamented with a strong crenulate-reticulate pattern.Setae z2 and J5 are simple and pointed, setae j4, z3, J3, and J5 pilose, and other setae plumose.Sternal shield crenulate-reticulate pattern, sternal setae plumose.Ventrianal shield is broader than long, and rounded laterally [1].In Indonesia, Glyptholaspis asperrima is distributed in Java, Kalimantan, and Sumatra [4,13,17,21,22].
Four species of Holostaspella were found in Sumatra.Females of this genus have dorsal shield setae 28-29 pairs, dorsal seta j1 short, enlarged, pilose or plumose and inserted on anterior projection.Femur II with spur ventrally.Of those four Holostaspella species, H. berlesei was found only in Sumatra while the other three species were also distributed in other islands in Indonesia.Holostaspella berlesei was first described based on a specimen from Congo [10] and is now distributed in Congo and Indonesia (Sumatra).
There were 13 species of the genus Macrocheles recorded from Sumatra.This genus is mostly described in the world, about 315 species have been described [2] while in Indonesia, 50 species of this genus have been reported.Genus Macrocheles is adaptable to the environment which releases gas such as dung habitat, compared to other genera [13].Characteristics of Macrocheles are a dorsal shield with 28-30 pairs setae, three pairs setae on the sternal shield, tripartite tectum, movable digit of chelicerae with bidentate tooth, and 6-7 setae on the genu IV.Three species of Neopodocinum, i.e.: N. bosschai, N. maius and N. subjaspersi were reported.Characteristics of this genus are a dorsal shield with 28-31 pairs setae, unipartite tectum, dorsal shield often with additional unpaired seta on posteromedial portion, anal shield rarely laterally expanded, peritreme looped posteriorly (straight on some species) and genu IV with 7-8 setae.

Association with insects (Scarabaeid dung beetles)
In Sumatra, Macrochelid mites are associated with some genera of dung beetles Scarabaeidae (Table 1).For two species, Geholaspis subspinosus and Holostaspella moderata, association with Scarabaeid dung beetles have not been reported.Based on the observation by Takaku (1994), many species of Macrochelidae, in particular genus Macrocheles, did not perform specific preference to species of dung (Scarabaeid) beetles [23].One species, H. moderata was found in a bird's nest.In 2013, this species also was found in the nest of a honey bee, Apis dorsata [22].
Macrochelidae attaches to the surface of dung beetles on the ventral side or leg in one habitat and will be brought to a new habitat when the dung beetles disperse.On the dung, the mites not only prey on nematodes or small insects but also may mate [1].This type of association was called phoresy.Phoresy may give some benefits for mite's dispersal.It helps mites move to new sources of food, habitats, and areas for colonization, avoid congested natal sites and prevent mites from inbreeding [24].

Potential use as a biocontrol agent
Macrochelidae is known as a predator of eggs and larva of flies and nematodes, and other small organisms such as Collembola.The potency of Macrochelidae as biological control agents of the organism relies on this predatory behavior.
Research using predatory mites for controlling agriculture pests has been done in many countries.Research on the laboratory's scale about predation by Macrochelidae has been reported by some researchers [25][26][27][28][29][30].In Indonesia, predation of eggs and larva of flies was been done by Hartini (1995) using M. merdarius.The result showed 50% of predation by this species.Only one species of Macrocheles, M. robustulus, has been commercialized for controlling egg and of Sciarid flies, thrips pupae and Lyprauta larvae [31].
One promising result of potential Macrochelidae for biocontrol is reported by Azevedo (2017).The author reported that Macrocheles embersoni and M. robustulus have a high potential for controlling stable flies (Stomoxis calcitrans), pest flies in cow farms, and Macrocheles muscaedomesticae for controlling egg and larva of Musca domestica [2].

Conclusions
There are 22 species of Macrochelid mites, belonging to five genera, in Sumatra, Indonesia.The occurrence of the genus Geholaspis is still doubtful and needs extensive research for this genus.Macrochelidae in Sumatra were associated with Scarabaeid beetles of the genera Catharsius, Onthophagus, Onitis, and Paragymnopleurus.The potency of Macrochelid mites in Sumatra as a biocontrol agent still needs intensive research.

Table 1 .
List of Macrochelid mites from Sumatra, Indonesia.