Introduction. The name of each listed species is followed by up to five sources that report the species as occurring in Michigan. Sources in all upper-case letters refer to specific insect collections: MSU-ARC refers to material held by the Michigan State University Arthropod Research Collection (data provided by G. Parsons). All others refer to collection data extracted from the Symbiota Collections of Arthropods Network (SCAN) database online at https://scan-bugs.org/. See the Methods page for a list of abbreviations and associated collections.
Species names preceded by a single '?' are considered probable (for occurring in Michigan) but uncertain records. Those preceded by '??' are considered possible but unlikely to occur in Michigan. Species that are fully accepted as having valid Michigan records are unmarked. Species reported in the literature that we consider to be erroneous Michigan records are in a separate list following the others.
Regarding this family Downie and Arnett (1996) write "In this family are found the smallest beetles, their length ranging between 0.25 and 1 mm. ... The following key [to the genera] is based on characters best seen from microscope slide preparations." And they also state "Twenty-two genera occur in North America north of Mexico. Probably there are more genera and many more undescribed species." If a Michigan specimen can be determined to genus, then for most genera it is possible to put a specific name on it (unless, of course, it is an undescribed species). The exception is the genus Acrotrichis, which is by far the largest genus in our area. For this genus Downie and Arnett write "The state of the literature is such that even most common species cannot be identified. Until the genus is revised there is little use trying to separate species."
PTILIIDAE
2 subfamilies, 6 tribes, 12 genera, 22 species
Subfamily Acrotrichinae
Tribe Acrotrichini
?Acrotrichis aspera (Haldeman, 1848): Hubbard and Schwarz (1878), MSU-ARC; reported from IL, IN & ON, unable to confirm ID of MSU specimen
Acrotrichis cognata (Matthews, 1877): Sörensson (2003)
??Acrotrichis dohrnii (Matthews, 1872): Hubbard and Schwarz (1878), MSU-ARC as Trichopteryx Dohrnii Matth.; very few records of this sp., known from NY & reported from OR, unable to confirm ID of MSU specimens
?Acrotrichis haldemani (LeConte, 1863): Hubbard and Schwarz (1878), MSU-ARC; known from RI & northward, perh. also from IN, unable to confirm ID of MSU specimens
Acrotrichis henrici (Matthews, 1872): Sörensson (2003)
??Acrotrichis parallela (Motschulsky, 1869): Hubbard and Schwarz (1878) as Trichopteryx parallela Mots.
Acrotrichis thoracica (Waltl, 1838): Sörensson (2003)
Acrotrichis volans (Motschulsky, 1845): Sörensson (2003), Downie & Arnett 1996
Tribe Nephanini
Ptiliopycna moerens (Matthews, 1874): Dybas (1978), Downie and Arnett (1996)
Smicrus filicornis (Fairmaire and Laboulbene, 1855): Schwarz (1876), Hubbard and Schwarz (1878), Leng (1920), Downie and Arnett (1996), MSU-ARC
Subfamily Ptiliinae
Tribe Nanosellini
Cylindroselloides dybasi Hall, 1999: Hall (1999)
Tribe Nossidini
Nossidium americanum (Motschulsky, 1869): Schwarz (1876), Hubbard and Schwarz (1878), Ruesink and Parsons (2023), MSU-ARC
Tribe Ptiliini
?Micridium lineatum (LeConte, 1863): Hubbard and Schwarz (1878), MSU-ARC(?); reported from IN (Blatchley, 1910), identity of MSU specimen uncertain
??Ptenidium evanescens (Marsham, 1802): Hubbard and Schwarz (1878); Löbl and Smetana (2007) say P. evanescens is a (doubtful) senior syn. of P. pusillum.
?Ptenidium pusillum (Gyllenhal, 1808): Leng (1920), Downie and Arnett (1996), MSU-ARC; MSU specimen from Detroit is correct genus but species uncertain
Ptenidium speculifer Matthews, 1884: Sörensson (2003)
?Ptiliola brevicollis (Matthews, 1860): MSU-ARC (?); the MSU specimens are probably correctly IDed but we are uncertain
?Ptiliola collani (Mäklin, 1853): Schwarz (1876), Hubbard and Schwarz (1878), Downie and Arnett (1996), MSU-ARC (?); the MSU specimen is probably correctly IDed but we are uncertain
Tribe Ptinellini
?Pteryx balteata (LeConte, 1863): Schwarz (1876), Hubbard and Schwarz (1878); Downie and Arnett (1996) say "the genus needs revision before any species can be correctly identified."
?Pteryx brunnea (LeConte, 1863): Hubbard and Schwarz (1878), Downie and Arnett (1996); Downie and Arnett (1996) say "the genus needs revision before any species can be correctly identified."
Ptinella quercus (LeConte, 1863): Schwarz (1876), Hubbard and Schwarz (1878), Ruesink and Parsons (2023), MSU-ARC
?Ptinellodes lecontei (Gemminger and Harold, 1868): Hubbard and Schwarz (1878), Downie and Arnett (1996); considered a SE U.S. species except for the Hubbard and Schwarz record
This family list was last updated: February 17, 2023