Asydates Casey, 1895

Mayor, Adriean J. & Gimmel, Matthew L., 2019, Revision of the Soft-Winged Flower Beetles of the Genus Asydates Casey, 1895 (Coleoptera: Melyridae: Dasytinae: Listrini), The Coleopterists Bulletin (mo 17) 73, pp. 1-71 : 4-6

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Asydates Casey, 1895


Asydates Casey, 1895

Asydates Casey 1895: 458 , 464. Type species: Asydates rufiventris Casey, 1895, fixed by subsequent designation (Blaisdell 1938: 20). Blaisdell 1924b: 17, 1938: 8, 20–21; Pic 1937: 90 (catalog); Arnett 1962: 611, 614; Majer 1990: 371; Mayor 2002: 284, 295; Mawdsley 2002a: 123–124 (taxonomy and key to some species).

Asydates sp.: Mayor 2002: 285, fig. 17.

Pristoscelis: LeConte 1866: 349 , 350–351 (in part); Bourgeois 1884: 289 (Note 1); Gorham 1891: 54; Casey 1895: 458, 459; Champion 1914: 90; Blaisdell 1924b: 17, 1938: 6, 11; Pic 1937: 90 (catalog); Arnett 1962: 609, 613; Majer 1990: 371; Mayor 2002: 284, 293, 295.

Pristocelis [sic]: Howell 1979: 45 (key to some species); 1997: 12–13 (key to some species).

Scelopristis Mayor 2004: 86 . Type species: Pristoscelis grandiceps LeConte, 1866, fixed by original designation (Mayor 2004: 86). New synonymy.

Diagnosis. The following characteristics distinguish species of Asydates from all other genera of Dasytinae : Tibial spurs acute, unmodified on all tibiae in both sexes; occipito-temporal and clypeofrontal regions of male head slightly to greatly enlarged, mouthparts and mandibles slightly to greatly elongated; male abdominal ventrite 1 with a more or less distinct median patch of pale, whitish setae; and apex of tegmen membranous, lacking setae on apical margin.

Description. Small, graciliform to large, moderately robust. Color variable, but typically not entirely black; legs, elytral apex, and female ventrites orange, or not; antennae and mouthparts typically darker red; elytra rarely more extensively orange. Pubescence variable, typically with all setae pale, reclining, rarely pale, reclining setae intermixed with black, erect setae on dorsal surface; apical margin of pygidium and apico-lateral margins of abdominal sternite VIII with dense tufts of long, black setae in both sexes. Male head megacephalous, occipito-temporal and clypeo-frontal regions, mouthparts, and mandibles slightly to greatly enlarged; female head unmodified. Antenna with 11 antennomeres, intermediate antennomeres slightly serrate, short, typically not reaching pronotal base posteriorly.

Pronotum moderately cylindrical, not explanate at lateral edge, wider than long, usually widest at or behind middle; pronotal lateral edges converging anteriorly, anterior angles not at all projecting; apical and basal margins broadly rounded; sublateral grooves or carinae completely absent. Elytra elongate, covering abdomen, apices more or less serrate; elytral epipleura variable, but occasionally very wide to near apex. Legs slender, elongate; tibiae with few to numerous spines on external surface, spines sometimes dense and comb-like; tibial spurs unmodified, acute on all legs in both sexes.

Male abdominal ventrite 1 with median patch of white setae, variable in development and density; female abdominal ventrite 5 broadly rounded posteriorly, with short, bristling setae in median third, longer, sparser setae laterally; male abdominal sternite VIII ( Figs. 21 View Fig , 22 View Fig ) membranous medially, without median strut. Male genital sclerites with apical portion of ring of tegmen ( Figs. 28 View Fig , 29 View Fig ) membranous, lacking apical setae; median lobe Lshaped, lying on its side in abdominal cavity; internal sac of aedeagus ( Figs. 24–27 View Fig View Fig View Fig View Fig ) with a cluster of large, more or less contiguous lamellae.

Relationships. No phylogenetic hypothesis has been produced for the North American Dasytinae . However, based on the morphology of male-based characters, in particular the lack of modified tibial spurs, the apically single-lobed median lobe of the aedeagus, the presence of a U-shaped cluster of large, dark sclerites in the seminal duct of the median lobe, the apically membranous and asetose tegmen, and the presence of modified setae on the abdominal ventrites, the genus Asydates may be sister to a group of species currently classified in the genus Trichochrous around the species Trichochrous umbratus (LeConte, 1866), which will be defined in a later publication.

Habitats. Adult Asydates are commonly found on flowers in a wide range of habitats, including coastal sage scrub, chaparral, deserts, mid-montane, and Great Basin grasslands ( Figs. 31 View Fig , 32 View Fig ). Adults are often preferentially associated with inflorescences of plants in the families Asteraceae , especially species of Stephanomeria Nutt. ( Figs. 33 View Fig , 34 View Fig , 35 View Fig ) and Chrysothamnus Nutt. ( Fig. 32A View Fig ), and Polygonaceae , especially species of Eriogonum Michx. ( Fig. 32B View Fig ). Immatures, as is the case with all species and genera of North American Dasytinae , are completely unknown.

Host Plant Associations. Based on label data, adults of Asydates have been collected from the flowers of plants in the families Anacardiaceae [ Malosma laurina (Nutt.) Nutt. ex Abrams]; Asteraceae [ Chaenactis carphoclinia A. Gray, Chrysothamnus viscidiflorus (Hook.) Nutt., Corethrogyne filaginifolia (Hook. & Arn.) Nutt., Ericameria arborescens (A. Gray) Greene, Ericameria nauseosa (Pall. ex Pursh) G. L. Nesom & G. I. Baird, Ericameria nauseosa consimilis (Greene) G. L. Nesom & G. I. Baird , Eriophyllum confertiflorum (DC.) A. Gray, Grindelia squarrosa (Pursh) Dunal, Haplopappus Cass. sp., Hemizonia fasciculata (DC.) Torr. & A. Gray, Isocoma acradenia (Greene) Greene, Lepidospartum squamatum (A. Gray) A. Gray, Palafoxia linearis Cav. (Lag.), Stephanomeria cichoriacea A. Gray, Stephanomeria exigua Nutt., Stephanomeria exigua Nutt. ssp. coronaria (Greene) Gottlieb , Stephanomeria pauciflora (Torr.) A. Nelson, and Stephanomeria virgata Benth.]; Bignoniaceae [ Chilopsis linearis (Cav.) Sweet]; Brassicaceae [ Brassica nigra (L.) W.D.J. Koch and Hirschfeldia incana (L.) Lagr.-Foss.]; Euphorbiaceae [no species given]; Fabaceae [ Senegalia greggii (A. Gray) Britton & Rose]; Loasaceae [ Mentzelia involucrata S. Watson and Mentzelia laevicaulis (Dougl. ex Hook.) Torr. & A. Gray]; Polygonaceae [ Eriogonum elongatum Benth., Eriogonum fasciculatum Benth., Eriogonum inflatum Torr., Eriogonum microthecum Nutt., Eriogonum nudum Douglas ex Benth., Eriogonum roseum Durand & Hilg., Eriogonum umbellatum Torr., and Eriogonum wrightii Torr. ex Benth.]; and Zygophyllaceae [ Larrea tridentata (DC.) Coville].

Geographic Range and Seasonal Distribution. Asydates species range from Alameda County in the southern Coast Ranges of California south to Baja California, Mexico, and in the Great Basin, Mojave, and Sonoran Deserts of California east to northwestern Arizona, Nevada , and Utah ( Fig. 36A View Fig ). Asydates shoshone Mayor and Gimmel, new species is only known to occur in the Great Basin Desert of eastern and central Nevada , and Asydates phantasma Mayor and Gimmel, new species is only known from two localities in eastern Utah on the Colorado Plateau. All Asydates species except A. shoshone and A. phantasma are known to occur in California, and Asydates chumash Mayor and Gimmel, new species, Asydates inexpectatus Mayor and Gimmel, new species, A. rufiventris, A. tongva Mayor and Gimmel, new species, and A. vandykei appear to be California endemics. Most remarkable is that seven species, A. chumash, Asydates grandiceps (LeConte) , Asydates irwini (Howell), Asydates ruficauda (Blaisdell), A. rufiventris, A. tongva, and A. vandykei, all have distributions that include the Transverse Ranges of southern California. This suggests the Transverse Ranges may be a center of origin for the genus Asydates , and/or that it may have served as a refugium during periods of contraction of species distributions.

Adults of Asydates occur from late spring through late fall, with most species active in mid-summer ( Figs. 39 View Fig , 40 View Fig ). Adults of all species except A. shoshone and A. inexpectatus have been collected in August, and since specimens of A. shoshone were collected in late July and September, we are sure that adults of this species are active in August as well. One species, A. irwini, has adults that may still be active in mid-December.

Remarks. The name Asydates is a rearrangement of letters in the genus name Adasytes Casey, 1895 . It is not a Latin or Greek word. In the original description of Asydates, Casey (1895) did not indicate the gender. However, Casey described Asydates explanatus Casey in 1895 as an originally included species, and this indicates that Asydates should be considered masculine (International Commission on Zoological Nomenclature 1999, ICZN Article 30.2.3).

The known species of Asydates are members of a genus in which males exhibit a form of megacephaly. In all species, there is a broadening and lengthening of the occipito-temporal region of the male head ( Howell 1979), a broadening of the clypeo-frontal region, and a lengthening of the mandibles, maxillae, and labium. While there is some variation among species in the degree of megacephaly, in general, these structures of the male head are slightly to greatly enlarged relative to body size. This character can be subtle but clearly observed when comparing males to females. Also, in males of all species, there is a more-or-less distinct median patch of white setae on abdominal ventrite 1 ( Fig. 19 View Fig ), and it is most distinct in males of A. ruficauda. Though not true of all species, in many Asydates the elytral epipleura are broad and planate to near the apex, with the lateral elytral margins clearly visible in dorsal view.

Known females of most species of Asydates have some or all of the abdominal ventrites pale red or orange, and at least one species name was based on this female character, resulting in the specific epithet Asydates rufiventris. In males of all species except A. inexpectatus, the abdominal ventrites are black with the exception of the terminal ventrite that, in some species, is apically pale red or orange. Surprisingly, in the male of A. inexpectatus, the abdominal ventrites are entirely orange to yellow-brown.


Asydates chumash Mayor and Gimmel, new species – California

Asydates grandiceps (LeConte, 1866), new combination (from Scelopristis ) – Mexico, California

Asydates inexpectatus Mayor and Gimmel, new species – California

Asydates irwini ( Howell, 1979), new combination (from Scelopristis ) – California, Utah

Asydates kumeyaay Mayor and Gimmel, new species – Mexico, California

Asydates phantasma Mayor and Gimmel, new species – Utah

Asydates ruficauda ( Blaisdell, 1924), new combination (from Trichochrous ) – California, Utah

= Pristocelis [sic] volki Howell, 1979, new synonymy

= Pristocelis [sic] schlingeri Howell, 1997, new synonymy

Asydates rufiventris Casey, 1895 – California

Asydates shoshone Mayor and Gimmel, new species – Nevada

Asydates tongva Mayor and Gimmel, new species – California

Asydates vandykei ( Blaisdell, 1924), new combination (from Scelopristis ) – California

Asydates washoe Mayor and Gimmel, new species – California, Nevada


The key to species is based primarily on males, and some females can only be reliably identified in association with males. However, where possible, female characters are used in the key. Differentiating males from females can be difficult. In general, males are more robust, including the antennomeres, and the antennae are longer. Females do not exhibit the megacephaly that is distinctive of males, and with practice the sexes can be distinguished on this character alone. Females also lack the distinctive white patch of setae on abdominal ventrite 1 that is characteristic of most males.

1. Body with erect or semi-erect, black setae on dorsal surface of elytra, in addition to reclining white or golden setae ( Fig. 7A–D View Fig ) ......................................... 2

1 ʹ. Body with only reclining white or golden setae on dorsal surface of elytra ( Figs. 7E–H View Fig , 8 View Fig , 9 View Fig ) .................................. 3












Asydates Casey, 1895

Mayor, Adriean J. & Gimmel, Matthew L. 2019

Asydates Casey 1895: 458

Majer 1990: 371
Arnett 1962: 611
Pic 1937: 90
Blaisdell 1924: 17
Casey 1895: 458


Majer 1990: 371
Arnett 1962: 609
Pic 1937: 90
Blaisdell 1924: 17
Casey 1895: 458
Bourgeois 1884: 289