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THE FAMILY PHYTOSEIIDAE (ACARI: MESOSTIGMATA)

Many species of Phytoseiidae are predators of mite pests; they are thus of huge interest in biological control programs (Kostiainen & Hoy, 1996; McMurtry & Croft, 1997). This family is widespread all over the world and includes three sub-families and more than 2,000 valid species.

 

 

 

 

 

Phytoseiidae Taxonomy

 

Some morphological elements

 

 

Phytoseiidae body is sclerotized and pyriform, its color varies from white to brown (Krantz, 1978). The lenght of the female body is about of 300 m, the males being slightly smaller. Phytoseiidae body is divided in two regions: the gnathosoma (anterior part) and the idiosoma (posterior part). The gnathosoma has a double function: sensorial and prey capture and ingestion. It bears sensorial palps, chelicerae and a stylophore. Chelicerae are constituted of a fixed digit which bears a variable number of teeth, a sensorial pilus dentilis (not for all the species) and a mobile digit which can be edentate. In males, chelicerae additionally bear a spermatodactyl on the mobile digit that allows spermatophore transfert from the male genital tractus to female genital apparatus (Amano & Chant, 1978; Evans, 1992). Idiosoma bears four pairs of legs (three in larvae) and each leg is constituted of six articles (Evans, 1992). The idiosoma is recovered by a dorsal shield and several ventral shields (three in females, two in males) (Chant, 1985 a,b). The female insemination apparatus (spermatheca) is localized in the anterior part of the coxa IV (Evans, 1992).

 

 

 

 

 

 

 

The development cycle of Phytoseiidae shows five stages: egg, hexapode larva, protonymph, deutonymph and adults (male and female). Eggs are usually translucide and ovals (Moraes & McMurtry, 1981; Sabelis, 1985a). Development duration varies from less than one week to four weeks depending on the species but also on climatic conditions and alimentation (Sabelis, 1985a). The temperatures at which Phytoseiidae can develop usually range between 10 and 30 C, the optimum usually being at 25 C. A high relative hygrometry (> 80 %) is usually favorable for egg and immature stage development (Sabelis, 1985a, Yoder, 1998). The fecundity ranges from 0.1 to 4.5 eggs / female / day depending on species (Kreiter et al., 1993). Phytoseiidae gravid females overwinter in temperate climates, under barks, dead leaves and buds (Veerman, 1992). Phytoseiidae reproduction is a pseudo-arrhenotoky. Fecundation (mating) is necessary to lay eggs. Males are haploid whereas the females are diploid. This haplo-diploidy could be due to inactivation / expulsion of male chromosome during the embryo formation (Nelson-Rees et al., 1980).

 

 

 

 

 

 

 

Some biological elements
The systematics of the family Phytoseiidae has a tumultuous and confused history due to a notable lack of agreement among taxonomists on the diagnostic characters that delimitate taxonomic entities (Chant & McMurtry, 2007). The number of valid phytoseiid species has increased exponentially from 34 in 1950 to more than 2,122 in 2010 (Moraes et al., 2004; Chant & McMurtry, 2007, Tixier et al., 2012). Phytoseiidae are included in 90 genera and three sub-families (Chant & McMurtry, 2007). These taxonomic entities are essentially defined according to chaetotactic patterns of the idiosoma. Phytoseiidae species diagnostic is based on the morphological characters of females, i.e. leg and idiosomal chaetotaxy (especially setal lengths), spermatheca shape and cheliceral dentition (Chant & McMurtry, 1994, 2007). The figure presents the seta nomenclature for dorsal and ventral shields for the three sub-families of Phytoseiidae (Amblyseiinae, Typhlodrominae and Phytoseiinae).

 

 

 

 

 

 

 

Some references

Amano H., Chant D.A. 1978. Mating behaviour and reproductive mechanisms of two species of predacious mites, Phytoseiulus persimilis Athias-Henriot and Amblyseius andersoni (Chant) (Acarina: Phytoseiidae). Acarologia, 20: 196-213.
Chant D.A. 1985a. Systematics and taxonomic. In: Spider Mites: Their Biology, Natural Enemies and Control. World Crop Pest. Vol. 1B, W. Helle et M. W. Sabelis eds., Elsevier. Amsterdam, 17-29.
Chant D.A. 1985b. External Anatomy. In: Spider Mites: Their Biology, Natural Enemies and Control.World Crop Pest. Vol. 1B, W. Helle et M.W. Sabelis eds., Elsevier. Amsterdam, 5-9.
Chant D.A., McMurtry J.A. 1994. A review of the subfamilies Phytoseiinae and Typhlodrominae (Acari: Phytoseiidae). International Journal of Acarology, 20 (4): 223-316.
Chant D.A., McMurtry J.A. 2007. Illustrated keys and diagnoses for the genra and subgenra of the Phytoseiidae of the word (Acai: mesostigmata). Indira Publishing House, Michigan, USA. 220 p.
Evans G.O. 1992. Principles of Acarology. CABI Publishing Wallingfrod, Oxon OX10 8DE, UK, 563 p.
Kostiainen T.S., Hoy M.A. 1996. The Phytoseiidae as biological control agents of pest mites and insects. A bibliography. Monograph 17, University of Florida, Agricultural Experiment Station, 355 pp.
Krantz G.W. 1978. A manual of Acarology, second edition. Oregon State University Book Stores, INC. Oregon State University, Corvallis, Oregon . 509 pp.
Kreiter S., Weber M., Sentenac G., Valentin G., Hardt P. 1993. Bilan de cinq années d'expérimentations de lutte biologique contre les acariens phytophages de la vigne à l'aide d'acariens prédateurs Phytoseiidae. Annales ANPP, 2: 341-349.
McMurtry J.A., Croft B.A. 1997. Life-styles of Phytoseiid mites and their roles in biological control. Annual Review of Entomology, 42: 291-321.
Moraes G.J., McMurtry J.A. 1981. Biology of Amblyseius citrifolius (Acarina: Phytoseiidae). Hilgardia, 49: 1-29.
Moraes G.J., McMurtry J.A., Denmark H.A., Campos C.B. 2004. A revised catalog of mite family Phytoseiidae. Zootaxa, 434,494 pp.
Nelson-Rees W.A., Hoy M.A., Roush R.T. 1980. Heterochromatization, chromatin elimination and haploidization in the parahaploid mite Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae). Chromosoma, 77: 263-276.
Tixier M.S., Kreiter S., Douin M., Moraes G.J. 2012. Rates of description of Phytoseiidae (Acari: Mesostigmata): space, time and body size variations. Biodiversity and Conservation, online first DOI 10.1007/s10531-012-0235-0.
Veerman A. 1992. Diapause in phytoseiid mites: a review. Experimental and Applied Acarology, 14 : 1-60.
Yoder J.A. 1998. A comparison of the water balance characteristics of Typhlodromus occidentalis and Amblyseius finlandicus mites (Acari: Phytoseiidae) and evidence for the site of water vapour uptake. Experimental and Applied Acarology, 22: 279-286.