Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Body narrow and elongate and with two dorsal shields
• Podonotal shield with 18 pairs of setae
• Female with entire sternal shield
• 2 pairs of scleronoduli
• Trochanter I with 5 or 6 setae; trochanter III with 4 setae; palpgenu with 6 setae
• Peritreme in adults and deutonymphs similar, reaching to about coxa II

Similar taxa

Other 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 most lack scleronoduli. Species of Longoseius (Longoseiulus) are less narrow than Longoseius (Longoseius) 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 described species of Longoseius (Longoseiulus) are found beneath bark in association with wood boring beetles in the families Cerambycidae, Elateridae and Pyrochroidae and are phoretic as deutonymphs under the elytra of the 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.