Mesostigmata

t

Taxonomy

updated 2025

Diagnostic characters

(NB—the deutonymph has been confused with adult female in several papers)

• Body extremely narrow and elongate and with two dorsal shields; podonotal shield deeply incised
• Podonotal shield with 12 pairs of setae; opisthonotal with 14–15 pairs (+/- J2); R1, 4, 5 in soft cuticle.
• Female with sternal shield split medially by soft cuticle, st1–2 and st3–4 on separate halves
• Scleronoduli absent or vestigial between setae z5
• Leg setation highly deficient, including trochanter I with only 5 setae; trochanter III with 4 setae; the palpgenu with only 5 setae.
• Peritreme in adults very short (restricted to coxa IV region), but elongate (to seta z4) in deutonymphs

Similar taxa

Other extremely narrow and elongate mesostigmatans are typically found in the pores of polypore fungi and have a holodorsal shield, e.g., see Mycolaelaps and Hoploseius tenuis. Although less elongate, some species of Protogamasellus and Protogamasellopsis somewhat resemble Longoseius (Longoseius) but have fuller setation, including seta z1 and j2 aligned with j1 on the anterior margin of the podonotal shield. Species of Longoseius (Longoseiulus) are less narrow and have scleronoduli and podonotal shields with full complements of j, z, and s setae.

Key to genera of Digamasellidae

1. Body extremely narrow and elongate, length 2.5–4 times width; trochanter III with 4 setae.............................. Longoseius
   - Body subrectangular to oval in shape; trochanter III with 5 setae.............................. 2

2. Scleronoduli present under podonotal shield between setae z5; anal opening normal; seta z3 present on podonotal shield.............................. 3
   - Scleronoduli absent; anal opening large; seta z3 absent from podonotal shield.............................. Digamasellus

3. Movable digit of female usually with 4 or more teeth; subcapitulum with 5 rows of denticles.............................. 4
   - Movable digit of female with 3 teeth; subcapitulum with 6 rows of denticles.............................. Dendroseius

4. Opisthonotal shield truncate or bilobed posteriorly and often with several pairs of spatulate setae; setae j2 inserted well behind setae j1–z1 on podonotal shield.............................. Dendrolaelaspis
   - Opisthonotal shield convex posteriorly and usually notched anteriorly; setae j2 more or less aligned with j1–z1 on podonotal shield.............................. Dendrolaelaps

Ecology and distribution

The two described species of Longoseius (L. cuniculus Chant; L. longus (Hirschmann)) are found beneath bark in association with wood boring beetles.

References

• Chant 1961Chant 1961:
  Chant DA. 1961. A new genus and species of mite in the family Digamasellidae Evans (Acarina). Acarologia 3: 11–13.
• Kinn 1984Kinn 1984:
  Kinn DN. 1984. Life cycle of Dendrolaelaps neodisetus (Mesostigmata: Digamasellidae), a nematophagous mite associated with pine bark beetles (Coleoptera: Scolytidae). Environmental Entomology 13 (4): 1141–1144.
• Lindquist 1975Lindquist 1975:
  Lindquist EE. 1975. Digamasellus Berlese, 1905, and Dendrolaelaps Halbert, 1915, with descriptions of new taxa of Digamasellidae (Acarina: Mesostigmata). The Canadian Entomologist 107: 1–43.
• Womersley 1954bWomersley 1954b:
  Womersley H. 1954b. Two new species of mites (Acarina: Mesostigmata: Ascidae) associated with bark-boring beetles from South Australia. Records of the South Australian Museum 11: 113–116.