Jacobsoniidae

Adults are minute (0.7–2.1 mm), with narrow bodies approximately four times as long as wide. Coloration is typically yellowish-brown. The body form is elongate and slender. Wing venation and larval maxillary galea morphology provide diagnostic characters distinguishing this family from other Staphylinoidea. Members are distinguished from similar minute beetles (particularly Ptiliidae) by combination of body proportions, antennal structure, and tarsal formula.

Leaf litter, rotting wood, fungal fruiting bodies, bat guano, caves, and resinous environments associated with resin-producing trees. Some species occur in ant nests.

Widely distributed but sporadically collected across tropical and subtropical regions. Extant records from: North America (Florida, Hawaii), Central America, South America, West Indies (Barbados, Guadeloupe, Montserrat, St. John, U.S. Virgin Islands), Polynesia, Africa (Tanzania—fossil in Holocene copal), India, Southeast Asia, China, Australia, New Zealand, New Caledonia, Papua New Guinea, Japan, and Mauritius. Fossil records from Cretaceous (Cenomanian) amber of Myanmar and France, Eocene Baltic amber, and Holocene copal of Tanzania. Not recorded from South American mainland.

Associated with fungi in soil and decaying organic matter; has been observed in fungal fruiting bodies.

Cryptic and difficult to detect due to minute body size. Long-distance dispersal likely facilitated by small size and feather-like hind wings, potentially including aerial transport. Some populations may represent accidental introductions through horticultural trade.

Possible indicators of undisturbed forest microhabitats and pre-Anthropocene biodiversity; their presence in resin deposits suggests association with resin-producing trees.

Presence in some regions (Hawaii, Florida, West Indies) may reflect accidental introduction via horticultural materials. Discovery in Holocene copal supports value of younger resins in documenting arthropod biodiversity prior to major human impact.

• PtiliidaeBoth are minute beetles within Staphylinoidea; distinguished by Jacobsoniidae's more elongate body (4× as long as wide vs. more compact in Ptiliidae) and different wing venation.
• HydraenidaeBoth Staphylinoidea families with small body size; Jacobsoniidae lack the aquatic or semi-aquatic adaptations typical of Hydraenidae and have different habitat associations.

• rare
• cryptic
• minute
• cave-dwelling
• fungus-associated
• relict
• morphological stasis
• Staphylinoidea
• tropical
• oceanic islands
• amber fossil
• copal fossil
• bradytely
• myrmecophilous?

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Derolathrus cavernicolus n. sp., a Beetle Family New for North America (Coleoptera: Jacobsoniidae)
• First record of Jacobsoniidae (Coleoptera) on the African continent in Holocene copal from Tanzania: biogeography since the Cretaceous