Taxonomy

Morphology

Phytoseiulus persimilis, ventrianal shield

Phytoseiulus persimilis, ventrianal shield of female © Peter York

The adult body is initially ovoid, but that of females becomes more widely rounded posteriorly as feeding and egg development progress. The first and last pairs of legs are longer than the body and the middle two slightly shorter. 

Characters

only present in the order Mesostigmata

  • A ribbon-like ventral peritreme (part of the respiratory system) runs along either side of the body just outside of the legs.
  • no setae on the small shields covering the anus 
  • anus opens within the ventrianal shield  (located on the underside of the body near to its posterior limit)
Character states
Phytoseiulus persimilis, peritrematal shield

Phytoseiulus persimilis female, anterior part of peritrematal shield © Peter York

that identify P. persimilis as a member of the family Phytoseiidae are: 

  • straight posterior margin of the female genital shield
    • shield located on the underside of the body, its anterior part between the bases of legs III-IV
  • a ventral anus
  • cheliceral digits of about the same size
  • one pair of J setae on the dorsal shield
  • separate sternogenital and ventrianal shields in the male 
Generic placement 

is based on the adult characters of:

  • leg tibia I has 
    • four dorsal (ad1-2, pd 1-2),
    • four lateral (al1-2, pl1-2) and 
    • three ventral (av1-2, pv1) setae (chaetotactic formula 2-2/2, 2/1-2); 
  • four pairs of setae (s4, Z1, Z4, Z5) are 
    • sparsely spiculed 
    • much thicker and longer than the other dorsal shield setae
  • dorsal setae j6 are several times longer than the distance between their bases
  • small female ventrianal shield has no preanal setae.  
Adult specific character states are:

 

  • On the single dorsal shield
    • setae j5 and S5 are present:
    •  z2 is on a level between j3 and j4;
    •  z2, z5 and J5 are smooth, the 
    • remaining ones are sparsely spiculed
    • setae j6 are ca. 3.7-4 times longer than the distance between their bases.
  • The peritrematal shield is fused to the dorsal shield anteriorly.
  • The cervix (=calyx) of the spermatheca (one located internally on either side of the body medial to the bases of legs III-IV) is very narrow in about its distal half and then flares just before the vesicle.
  • Leg IV has a sparsely spiculed macroseta on the genu and tibia, and a smooth one on the basitarsus.
  • The female sternal shield has three pairs of setae (st1-st3), 
  • the ventrianal shield bears only the postanal and paranal setae (preanal setae absent).

(Athias-Henriot, 1957; Takahashi and Chant, 1993b)

Genetics

Chromosome number 8 (diploid), 4 (haploid). (Wysoki, 1985)