Introduction

Soil is an important and biologically diverse habitat on Earth. The soil enriched with organic matter is considered to contain 20 different linages of Arthropoda, which represent 85% of total soil fauna (Culliney 2013). Mites (Acari) are the largest group of arthropods, competent to insects and total taxonomically described mite species are 55214 from various ecosystems which constitute the major diversity of the arthropods (Zhang 2013). Among other soil arthropods, total relative abundance of Mesostigmata was recorded up to 43.31% (Desmond and Ugwumba 2013). The mites (Acari) are one of the most abundant groups of arthropods. Due to their evolutionary history and having small size, mites can be found in all types of habitats. Based on such characteristics, 55000 species of mites have been described and still more than million species of mites are yet to be described (Walter and Proctor 1999). Likewise, total mite species are much more than this current estimate of million or more (Gaston 1991). Among these, mites (Acari) and collembolans are most abundant. Mesostigmata alone contributes about 80% of soil arthropod fauna (Petersen and Luxton 1982; Minor and Norton 2004). Free living mesostigmatid mites are found in all types of habitats like soil, litter, dung, plants and decaying wood (Walter and Olivier 1989; Halliday 2000; Shaw and Walter 2003). Being predators, they are unable to impart major structural changes of soil as well as their direct role for enhancing the crop production is also negligible, while indirectly they can regulate the populations of other organisms due to their predation rates (Koehler 1997, 1999; Gulvik 2007; Salmane and Brumelis 2008). These mites are mostly found in soil below litter and humus layers. A substantial part of these mites are also found from 4–6ʺ soil layers (Krantz and Ainscough 1990). Diversity and abundance of Mesostigmata change during different seasons and found maximum during first six month of the year as compared to last six months. Maximum diversity was found during May, June, July and August. Also abundance was maximum in upper litter layer (34%), minimum recorded from soil depth of 10–15 cm (14%). Different factors like seasonal variation, soil depth and above ground plant species post great impact on abundance of Mesostigmata (Urhan et al. 2008).

Being predacious nature to control population of many pests, even some of these mites have such potential to control many herbivorous pests that spend some time of their life cycle within the soil, plant roots or litter (Eickwort 1983; Lesna et al. 1995; Koehler 1999; Gerson et al. 2003; Beaulieu and Weeks 2007). Thrips are important pest of citrus (Blank and Gill 1997; Marullo 1998; Mound and Jackman 1998; Varikou et al. 2002; Navarro-Campos et al. 2011) that damage the fruit by scraping tissues and formation of uniform ring, hence destroy the cosmetic value of such fruits and also unsalable in quality market (Jeppson 1989; Crisp and Baker 2011). Because thrips pupate within soil (as pseudo pupae) and mesostigmatid mites have ability to find and control the population of soil dwelling thrips efficiently (El-Titi and Ipach 1989). Many studies have reported from different parts of the world which exhibit that mesostigmatid mites can successfully feed and control thrips (El-Banhawy et al. 2006; Messelink and Holstein-Saj 2008). From Pakistan, no studies on the diversity of Mesostigmata have been carried out so far. Keeping in view the importance of this group, the present research was conducted to explore the diversity of soil inhabiting Mesostigmata from citrus orchards of Punjab.

Materials and Methods

Four citrus growing districts of Punjab viz., Faisalabad, Sargodha, Toba Tek Singh and Layyah were selected. Three orchards were selected from each site having similar agronomic and pest management practices. Three samples were collected from each site. Soil samples were collected at monthly interval from each site with the help of a steel core measuring one litre capacity (10.5 cm diameter and 12 cm length). The soil was transferred to zip lock polythene bags to avoid the escape of mites and moisture contents from samples. These samples were transferred immediately to Acarology Research Laboratory, Department of Entomology, University of Agriculture, Faisalabad. The modified Berlese Tulgren Funnels apparatus was used to extract the mites from collected samples. The soil samples were processed for 48 h to ensure the maximum collection of mites from the collected ones. The specimens were preserved in mini vials containing 75% ethanol and few drops of glycerine. Vials were tagged according to date of collection and locality, for further studies. These collected specimens were sorted and mounted permanently in Hoyer’s medium under a stereoscope. The mounted specimens were studied under higher power phase contrast microscope (Meiji Techno MT4210H). The specimens were identified up to family level by using taxonomic keys of Krantz and Walter (2009) and Evans and Till (1979).

The individual-based rarefaction curves were calculated by using computer software ‘PAST’ (Hammer et al. 2001). Abundance of the mites recorded as the number of individuals per sample. Family richness was expressed as the number of families represented per sample while the Shannon-Weiner diversity index was calculated the represented the diversity of soil mites per sample. Chao 1 diversity index was also calculated to compute the richness of soil inhabiting mites to evaluate the rare number of families that may be missed due sampling methods (Chao 1984). Data of various factors was subject to ANOVA while Turkey’s pair-wise comparison (Fisher test) was applied. These analyses were performed using R software with a significance level of α=0.05.

Results

Individual base rarefaction analysis was done for cumulative soil mite data and four selected sites viz., Faisalabad, Sargodha, Toba Tek Singh and Layyah for assessment whether the number of samples collected was enough to represent the maximum taxa. Standard curves obtained as a result of rarefaction analysis showed different data sets based on number of individuals. These individual based rarefaction curves for all the selected districts of Punjab showed that sampling effort was enough and represented the maximum taxa of mesostigmatid mites obtained from soil samples during this study (Fig. 1).

The sampling resulted in collection of 3431 mesostigmatid mites out of 11250. Shannon diversity of all the four different districts varied slightly, maximum value of Shannon diversity index (Hꞌ=2.12) was recorded for Sargodha followed by Faisalabad (Hꞌ=2.03) while minimum (Hꞌ=1.90) was reported for Layyah and Toba Tek Singh districts (Table 1). The Fisher’s Alpha diversity index also varied slightly between four districts and maximum value (1.65) was recorded from Toba Tek Singh followed by Sargodha (1.51), Layyah (1.36) and Faisalabad (1.34) (Table 1). The Chao1 diversity index of Mesostigmata of citrus orchards of four districts of Punjab revealed slight variations. Maximum number of families per district Chao1 (S. obs.) value (10) was observed from Faisalabad and Sargodha districts while minimum (S. obs.= 9) was recorded from Layyah and Toba Tek Singh districts. This result showed that observed and chao1 estimator was same and represented the number of families per district of mesostigmatid mites of citrus orchards of four districts of Punjab (Table 2). Maximum value of Shannon Diversity (Hꞌ) was reported in June (Hꞌ=2.23) whereas, the maximum value of Fisher’s alpha 2.85 in the same moth (Table 3). Month wise Chao1 diversity index values are given in Table 4 which represents no variation during all the year.

Data regarding the abundance showed highly significant differences in all the districts (F_value =8.26; P ≤ 0.000). The maximum mean values of abundance of Mesostigmata (9.67 ± 0.60) were recorded from Layyah and minimum (7.50 ± 0.55) from Toba Tek Singh. Faisalabad showed 8.03 ± 0.57 and Sargodha 7.53 ± 0.54 mean abundance. Different months also showed highly significant variations (F_value =24.79; P ≤ 0.000). Maximum population reported was 12.92 ± 0.99 during April followed by 12.25 ± 1.14, 11.33 ± 0.97 and 9.33 ± 1.09 in March, June and January, respectively. All these are statistically at par. Minimum abundance was reported during 4.08 ± 0.48 in November, which was statistically similar to October (4.22 ± 0.53) December (4.61 ± 0.40) and August (5.69 ± 0.55) (Table 5). Interaction of months and districts also had significant differences (F_value=9.04; P ≤ 0.000).

Table 1: Shannon diversity and Fisher’s alpha index of Mesostigmata from different districts

Districts	Shannon diversity	Fisher's alpha
Faisalabad	2.03	1.34
Layyah	1.90	1.36
Sargodha	2.12	1.51
Toba Tek Singh	1.90	1.65

Table 2: Observed and estimates no. of families of soil mesostigmatid mites based on Chao 1 estimator in relation to citrus orchards from different districts of Punjab

Districts	Observed	Estimated
		Chao1	S. ACE
Faisalabad	10	10	10
Layyah	9	9	9
Sargodha	10	10	10
T.T. Singh	9	9	9

Fig. 1: Rarefaction curve for cumulative data of citrus orchards of Punjab

Table 3: Month wise Shannon diversity and Fisher’s alpha index of Mesostigmata

Month	Shannon diversity	Fisher's alpha
January	2.01	2.59
February	2.05	2.29
March	1.98	2.08
April	1.97	2.03
May	2.07	2.18
June	2.23	2.85
July	2.13	2.72
August	2.15	2.13
September	2.04	2.08
October	2.01	2.09
November	2.08	2.24
December	2.08	2.44

Table 4: Observed and estimates no. of families of soil mesostigmatid mites based on Chao 1 estimator in relation to citrus orchards during different months

Months	Observed	Estimated
		Chao1	S. ACE
January	10	11	11.63
February	11	11	11
March	11	11	11
April	11	11	11
May	11	11	11
June	11	11	11
July	10	10	10
August	11	11	11
September	11	11	11
October	11	11	11
November	11	11	11
December	11	11	11

Data of richness expressed highly significant variations in all the districts (F_value =49.49; P ≤ 0.000). The maximum mean values of richness of Mesostigmata (4.69 ± 0.20) were reported from Layyah and minimum (3.88 ± 1.72) from Sargodha. Faisalabad showed 4.22 ± 1.21 and Toba Tek Singh 3.98 ± 1.95 (mean richness). Different months also showed highly significant variations (F_value =3.307; P ≤ 0.000). Maximum richness reported was 5.94 ± 0.32 during April followed by 5.42 ± 36 and 5.42 ± 30 in June and March, respectively. All these are statistically at par. Minimum richness was reported during 2.53 ± 0.27 in October, which was statistically similar to November 2.69 ± 0.27 (Table 6). Interaction of months and districts also had significant differences (F_value= 3.18; P ≤ 0.000).

Data of community structure of soil Mesostigmata from different districts of Punjab showed that Pachylaelapidae, Rhodacaridae and Uropodidae was found maximum form Faisalabad, Ameroseiidae, Ascidae, Macrochelidae, Parasitidae and Sejidae was recorded maximum form citrus orchards of Sargodha, Phytoseiidae was found maximum from Toba Tek Singh and Melicheridae form Layyah. While family Melicheridae was not found form Faisalabad and Sargodha, Rhodacaridae from Toba Tek Singh, Sejidae from Layyah and Toba Tek Singh and Uropodidae was nil in Layyah (Fig. 2). The month wise community structure showed that population of Laelapidae was maximum during April and October, Pachylaelapidae, Ameroseiidae, Phytoseiidae in April, Parasitidae and Macrochelidae in September, Melicheridae and Uropodidae in August, Ascidae in March, Sejidae in October and Rhodacaridae in month of December, respectively (Fig. 3).

Table 5: Abundance of mesostigmatid mites from different Districts during different months

Month	FAISALABAD				LAYYAH				SARGODHA				TOBA TEK SINGH
	Mean	+	S.E.		Mean	+	S.E.		Mean	+	S.E.		Mean	+	S.E.		Averages
January	2.78	±	0.49	ef	14.67	±	2.40	a	13.33	±	1.26	ab	6.56	±	1.20	c	9.33 ± 1.09 A
February	11.33	±	1.44	b	15.33	±	2.87	a	4.56	±	0.99	d	4.44	±	0.47	cd	8.92 ± 1.13 BC
March	17.78	±	1.62	a	5.33	±	0.94	cd	9.67	±	1.32	c	16.22	±	2.21	a	12.25 ± 1.14 A
April	7.67	±	2.13	cd	13.22	±	0.89	a	16.11	±	2.23	a	14.67	±	1.34	a	12.92 ± 0.99 A
May	10.00	±	1.31	bc	13.44	±	2.35	a	3.00	±	0.65	de	3.67	±	0.83	cd	7.53 ± 1.01 C
June	15.44	±	1.42	a	8.89	±	1.59	b	9.78	±	2.25	c	11.22	±	1.91	b	11.33 ± 0.97 A
July	1.67	±	0.53	f	15.56	±	1.42	a	10.11	±	1.21	bc	6.56	±	0.82	c	8.47 ± 0.99 BC
August	9.00	±	0.71	bc	7.11	±	0.77	bc	3.11	±	0.81	de	3.56	±	0.78	cd	5.69 ± 0.55 D
September	7.00	±	0.82	cd	7.89	±	1.20	bc	9.89	±	1.36	c	10.44	±	1.04	b	8.81 ± 0.59 BC
October	1.22	±	0.64	f	7.11	±	0.54	bc	5.56	±	0.85	d	3.00	±	0.91	d	4.22 ± 0.53 D
November	7.00	±	0.37	cd	5.22	±	0.46	cd	1.00	±	0.33	e	3.11	±	0.99	d	4.08 ± 0.48 D
December	5.44	±	0.75	de	2.22	±	0.49	d	4.22	±	0.43	de	6.56	±	0.77	c	4.61 ± 0.40 D
Overall Means	8.03	±	0.57	B	9.67	±	0.60	B	7.53	±	0.54	A	7.50	±	0.55	B

Means sharing similar letters are non-significant (P ≥ 0.05); Small letters in each column represent differences between months at each locality while capital letters in the last column represent month wise difference in all localities, capital letters in last row, represent overall difference in each locality

Table 6: Richness of mesostigmatid mites from different Districts during different months

Months	Faisalabad				Layyah				Sargodha				Toba Tek Singh
	Mean		SE		Mean		SE		Mean		SE		Mean		SE		Averages
January	2.44	±	0.38	d	5.56	±	0.29	ab	6.00	±	0.41	ab	4.22	±	0.36	cd	4.56 ± 0.29 B
February	5.67	±	0.55	ab	5.78	±	0.52	ab	3.11	±	0.61	d	3.33	±	0.33	def	4.47 ± 0.32 B
March	6.89	±	0.35	a	3.78	±	0.62	d	5.00	±	0.33	bc	6.00	±	0.50	ab	5.42 ± 0.30 A
April	3.78	±	0.70	c	6.33	±	0.33	a	6.56	±	0.41	a	7.11	±	0.42	a	5.94 ± 0.32 A
May	5.22	±	0.46	b	6.22	±	0.52	a	2.33	±	0.53	d	3.00	±	0.58	defg	4.19 ± 0.37 BC
June	6.67	±	0.44	a	4.89	±	0.77	bcd	5.11	±	0.79	bc	5.00	±	0.78	bc	5.42 ± 0.36 A
July	1.22	±	0.32	de	5.33	±	0.33	abc	4.67	±	0.29	c	3.44	±	0.29	def	3.67 ± 0.30 CD
August	5.33	±	0.41	b	4.56	±	0.38	bcd	2.11	±	0.51	de	2.78	±	0.60	efg	3.69 ± 0.32 CD
September	4.56	±	0.56	bc	4.22	±	0.36	cd	5.00	±	0.44	bc	4.89	±	0.39	bc	4.67 ± 0.22 B
October	1.11	±	0.54	e	3.89	±	0.39	d	3.11	±	0.35	d	2.00	±	0.33	g	2.53 ± 0.27 E
November	3.89	±	0.20	c	3.78	±	0.28	d	0.89	±	0.26	e	2.22	±	0.60	fg	2.69 ± 0.27 E
December	3.89	±	0.39	c	2.00	±	0.50	e	2.67	±	0.17	d	3.78	±	0.40	cde	3.08 ± 0.23 DE
Overall Means	4.22	±	1.21	B	4.69	±	0.20	B	3.88	±	1.72	A	3.98	±	1.95	B

Means sharing similar letters are non-significant (P ≥ 0.05); Small letters in each column represent differences between months at each locality while capital letters in the last column represent month wise difference in all localities, capital letters in last row, represent overall difference in each locality

Discussion

The present study resulted in collection of 3431 specimens of Mesostigmata which makes 30% of total collected specimens of soil inhabiting mites from all the four regions. These results are closely similar to the results of Banerjee et al. (2009) who reported 27.22% from West Bengal, whereas, Desmond and Ugwumba (2013) also reported 43.31% abundance of Mesostigmata while Imen et al. (2018) reported 43.99% relative abundance of mesostigmatid soil mites from citrus orchards. The Shannon diversity (Hꞌ) of the citrus orchards of different regions varied from 1.90–2.12, these results are in close agreement of Khan et al. (2017) who reported a maximum of 1.93 (Hꞌ) for soil inhabiting Mesostigmata from D.G. Khan. These results reveal that the citrus orchards are rich in predatory fauna of this very important group. The results very clearly indicate that a varying overall mean value mesostigmatid soil mites from all districts during different months with abundance values ranging from 12.92 to 4.08 have been reported during April and November respectively. These results are in line of findings reported by Imen et al. (2018). The availability of predatory mites of Mesostigmata is a sign of soil health and results of this study showed that maximum 1.62 individuals per sample during month of September from Faisalabad and minimum 0.00 individuals per sample of mesostigmatid mites from Layyah have been collected during month of July. The studies in different parts of the world have revealed as low as 0.25 individuals per sample mesostigmatid mites (Usher 1971). In comparison with other natural ecosystem, density of Mesostigmata of citrus orchard was low as reported by Hermosilla et al. (1977), Curry and Monem (1988), Hulsmann and Wolters (1998). However, some other workers like Koehler (1999); Bedano and Cantú (2003) reported high density of Mesostigmata. Community structure of mesostigmatid soil mites from different districts showed great variations and results are in the line of findings of Khan et al. (2017). Similarly, community structure for different months showed great variation and each family showed maximum population during different months and results are in agreement with

Fig. 2: Community Structure of Mesostigmata from Different Districts

Fig. 3: Community Structure of Mesostigmata during different months

Imen et al. (2018). Reasons for this variation may be due to the soil parameters including organic matter, use of agrochemicals and agronomic practices.

Conclusion

The soils of citrus orchards of Punjab are rich in mesostigmatid fauna. These mites remain available throughout year and can play an important role in pest management. Further studies are needed on species level to find an appropriate predator against specific pests.

References

Banerjee S, AK Sanyal, MN Moitra (2009). Abundance and group diversity of soil mite population in relation to four edaphic factors at Chintamani Abhayaranya, Narendrapur, South 24-Parganas, West Bengal. Proc Zool Soc 62:57‒65

Beaulieu F, AR Weeks (2007). Free-living Mesostigmataa mites in Australia: their roles in biological control and bioindication. Aust J Exp Agric 47:460‒478

Bedano JC, MP Cantú (2003). Los microartrópodos edáficos de un Argiudol típico no alterado de la cuenca del arroyo El Bañado, Córdoba, Argentina. Neotropica 49:1‒10

Blank RH, GSC Gill (1997). Thrips (Thysanoptera: Terebrantia) on flowers and fruit of citrus in New Zealand. New Zeal J Crop Hort Sci 25: 319‒332

Chao A (1984). Nonparametric estimation of the number of classes in a population. Scand J Stat 11:265‒270

Crisp P, G Baker (2011). Soil mediated conservation biological control of Kelly’s citrus thrips Pezothrips kellyanus pupae. IOBC/WPRS Bull 62:239‒246

Culliney TW (2013). Role of arthropods in maintaining soil fertility. Agriculture 3:629‒659

Curry JP, F Momen (1988). The arthropod fauna of grassland on reclaimed cutaway peat in Central Ireland. Pedobiologia 32:99‒109

Desmond AOD, UO Ugwumba (2013). A comparative assessment of soil arthropod abundance and diversity in practical farmlands of University of Ibadan, Nigeria. Intl J Environ Resour Res 1:17‒29

Eickwort GC (1983). Potential use of mites as biological control agents of leaf-feeding insects. In: Biological Control of Pests by Mites, pp:41–52. Hoy MA, GL Cunningham, L Knutson (eds.). University of California Press, Berkeley, California, USA

El-Banhawy EM, AK Nasr, SI Afia (2006). Survey of predacious soil mites (Acari: Mesostigmata) in citrus orchards of the Nile Delta and Middle Egypt with notes on the abundance of the citrus parasitic nematode Tylenchulus semipenetrans (Tylenchida: Tylenchulidae). Intl J Trop Ins Sci 26:64–69

El-Titi A, U Ipach (1989). Soil fauna in sustainable agriculture: Results of an integrated farming system at Lautenbach, FRG. Agric Ecol Environ 27:561‒572

Evans GO, WM Till (1979). Mesostigmata mites of Britiain and Ireland Chelicerate: Acari-Parasitiformes). An introduction of their external morphology and classification. Trans Zool Soc Lond 35:139–262

Gaston KJ (1991). The magnitude of global insect species richness. Conserv Biol 5:283‒296

Gerson U, RL Smiley, R Ochoa (2003). ‘Mite (Acari) for Pest Control. Blackwell Science, Oxford, UK

Gulvik M (2007). Mites (Acari) as indicators of soil biodiversity and land use monitoring: a review. Pol J Ecol 55:415–440

Halliday RB (2000). The Australian species of Macrocheles (Acarina: Macrochelidae). Invertebr Syst 14:273‒326

Hammer Ø, DA Harper, PD Ryan (2001). PAST: paleontological statistics software package for education and data analysis. Palaeontol Electr 4:1–9

Hermosilla W, A Reca, J Pujalte, I Rubio (1977). Efectos de la compactación del suelo sobre la fauna edáfica en campos pastoreados (Partido de Chascomús, Provincia de Buenos Aires - Argentina). Physis 36:227‒236

Hulsmann A, V Wolters (1998). The effects of different tillage practices on soil mites, with particular reference to Oribatida. Appl Soil Ecol 9:327‒332

Imen BK, LM Maria, BK Synda (2018). New records of soil mites (Acari) from citrus orchards of Tunisia. J Entomol Zool Stud 6: 1461‒1466

Jeppson LR (1989). Biology of citrus insects, mites and mollusks. In: The Citrus Industry, Vol. 5, pp:1‒87. Reuther W, EC Calavan, GE Carman (Eds.). University of California, Oakland, California, USA

Khan AK, MH Bashir, BS Khan, N Javed (2017). Biodiversity of Soil Inhabiting Mesostigmata (Arachnida: Acari) from Different Agro-Ecological Zones of Punjab, Pakistan. Pak J Zool 49:677‒683

Koehler HH (1999). Predatory mites (Gamasina, Mesostigmataa). Agric Ecosyst Environ 74:395‒410

Koehler HH (1997). Mesostigmataa (Gamasina, Uropodina), efficient predators in agroecosystems. Agric Ecosyst Environ 62:105‒117

Krantz GW, DE Walter (2009). A Manual of Acarology, 3^rd ed. University Press, University of Texas, Austin, Texas, USA

Krantz GW, BD Ainscough (1990). Acarina: Mesostigmata (Gamasida). In: Soil biology guide, pp:583–665. Dindal DL (Ed.). A Wiley-Interscience PublicationLesna I, MW Sabelis, HR Bolland, CGM Conijn (1995). Candidate natural enemies for control of Rhizoglyphus robini Claparède (Acari: Astigmata) in lily bulbs: exploration in the field and pre-selection in the laboratory. Exp Appl Acarol 19:655‒669

Marullo R (1998). Pezothrips kellyanus un nuovo thripide parassita delle culture meridionali. Infrom Fitopatol 10:72‒74

Messelink G, RV Holstein-Saj (2008). Improving thrips control by the soildwelling predatory mite Macrocheles robustulus (Berlese). IOBC/WPRS Bull 32:135–138

Minor MA, RA Norton (2004). Effects soil amendments on the assemblages of Mesostigmata (Acari: Oribatida. Mesostigmataa) in short rotation willow planiings in central New York. Can J For Res 34:1417‒1425

Mound LA, DJ Jackman (1998). Thrips in the economy and ecology of Australia. In: Proceedings Of the Sixth Australian Applied Entomological Research Conference, Vol. 1, pp:472‒478. University of Queensland, Brisbane, Australia

Navarro-Campos C, A Aguilar, F Garcia-Mari (2011). Population trend and fruit damage of Pezothrips kellyanus in citrus orchards in Valencia (Spain). IOBC/WPRS Bull 62:285‒292

Petersen H, MA Luxton (1982). Comparative analysis of soil fauna populations and their role in decomposition processes. Oikos 39:288‒388

Salmane I, G Brumelis (2008). The importance of the moss layer in sustaining biological diversity of Gamasina mites in coniferous forest soil. Pedobiologia 52:69‒76

Shaw M, DE Walter (2003). Hallowed hideaways: basal mites in tree hollowsand allied habitats. In: Arthropods of Tropical Forests: Spatio-temporal Dynamics and Resource use in the Canopy, pp:291‒303. Basset Y, V Novotny, SE Miller, RL Kitching (Eds.). Cambridge University Press, Cambridge, UK

Urhan R, Y Katilmis, AO Kahveci (2008). Vertical distribution of Mesostigmata (acari) in Dalaman (Mugla Prov. Turkey). Mun Entomol Zool 3:333‒341

Usher MB (1971). Properties of the aggregations of soil arthropods, particularly Mesostigmata (Acarina). Oikos 22:43‒49

Varikou K, JA Tsitsipis, V Alexandrakis, L Mound (2002). Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae), a new pest of citrus trees in Crete. In: Proceedings Of the VIIth European Congress Of Entomology, pp:7–13. DTP Artwork Thessaloniki, Greece

Walter DE, HC Proctor (1999). Mites: Ecology, Evolution and Behavior, p:322. University of NSW Press, CABI, Wallingford, UK

Walter DE, JH Olivier (1989). Geolaelaps oreithyiae n. spp. (Acari: Laelapidae) a thelytokous predator of arthropods and nematodes and a discussion of clonal reproduction in the Mesostigmata. Acarologia 30:293‒303

Zhang ZQ (2013). Phylum Arthropoda. Animal biodiversity: An outline of higher level classification and survey of taxonomic richness. Zootaxa 3703:17‒26