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.
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 µm, 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.