Genus Trichiotinus - Hairy Flower Scarabs

Flower Beetle, Bee-Like Flower Scarab (used by Papp (1) for T. piger)

Author of genus is Casey, 1915. These beetles were originally placed in the similar Eurasian genus Trichius. Name is probably derived from Trichius, and the suffix inus is a diminutive? Trichos is Greek, hair. Trichius means hairy? (Based on Internet searches.)

Arnett (2) and Nearctica.com both list eight North American species.

7-12 mm

Diurnal scarabs that visit flowers. Compact shape, not elongated. Very hairy on abdomen--the hairs often poking out prominently from under the elytra. Identification of species is somewhat difficult, requiring close examination. Range info below can be useful. Visually there are two groups:

1-Pronotum brown or black, elytra brown/black center, white stripes along sides:

* assimilis - mostly northern and western

* affinis - similar to piger, but (after Howden 1968); Elytral intervals 2 and 4 shiny, with scattered large punctures, their appearance same as slightly elevated and convex intervals 3 and 5; pygidium distinctly and closely rugose

* piger - very similar to affinis, but (after Howden 1968); Elytral intervals 2 and 4 finely and densely punctate, less shiny than distinctly elevated and convex intervals 3 and 5; pygidium medially distinctly setose, noncretaceous surface with irregular rugae usually separated by less than or equal to 0.2 mm in median area

* rufobrunneus - very brown, Florida endemic

* texanus

The striped pattern is perhaps mimicry of banded hymenoptera. Trichiotinus tend to have a buzzy flight, reminiscent of bees.

2-Pronotum green, elytra brown to green in varying degrees, with no or weak white bars:

* bibens - elytra brown with green tinge, flies in mid-late summer

* lunulatus - elytra brighter green than bibens, flies in late spring and early summer, overlooked by Downie & Arnett for the Northeast. (3)

* viridans - Specific name means "green".

With their coloration and diurnal habits, perhaps the bright green coloration is mimicry of hymenoptera such as sweat bees (Halictidae) and Cuckoo Wasps (Chrysididae).

Genus Nearctic, primarily eastern US.

* affinis - Canada; eastern US: Maine, Illinois, Alabama, Florida.

* assimilis - Canada; northern and western US: Maine, Michigan, Nebraska, Idaho, Arizona and New Mexico.

* bibens - Eastern US: Michigan, southern New York, northern Georgia and Alabama.

* lunulatus - Southeastern US: Virginia, Maryland, Florida to Texas and Oklahoma.

* piger - Canada; eastern US: Maine to Florida, west to Arizona, Texas and Nebraska.

* rufobrunneus - Florida endemic.

* texanus - New Mexico, Texas, Oklahoma, Kansas.

* viridans - Canada; upper midwest US: Illinois, Indiana, Iowa, Kansas, Michigan and Wisconsin.

Open areas with flowers, near woodlands.

Spring-summer (April-August)

Adults take pollen and/or nectar from such flowers as Queen Anne's Lace, New Jersey Tea, hydrangea, Dogwood, and Indian Hemp. Also feed on vegetative parts?

Larvae live in rotting wood (4). Adults visit flowers. Diurnal, do not come to lights.

Sometimes misspelled "Trichotinus".

I've coined the common name for the genus as a whole.

Often occur on flowers alongside Flower Longhorns and the Delta Flower Scarab.

White describes genus (p.147) and illustrates T. piger (4).

Arnett and Jacques, plate 115, have a photo of T. affinis, #115 (5).

Dillon, describes genus, pp. 554-555, gives key to three species, illustrate T. affinis, bibens, and piger, plate LIV. (6)

Papp, page 194, fig. 660, illustrates T. piger. (1).

Arnett, page 182, fig. 445, illustrates T. piger. (7).

Borror and White, plate 7 #1, illustrate T. affinis, Trichiotinus species, p. 195. (8)

Deyrup, page 95, shows two species of this genus, but does not name them. They are possibly T. lunulatus or affinis--brown/green, and T. rufobrunneus--dark reddish brown, a Florida endemic. (9).

Harpootlian, pp. 122-123, gives a key to the four species found in South Carolina. (10)

Salsbury, p. 185, illustrates T. texanus. (11)

Insects of Cedar Creek: T. assimilis

Insects of Quebec has photo of T. assimilis

Another species from Canada, perhaps T. assimilis

Illustration by Joe MacGown of T. "affinus", meaning affinis

T. "bidens", meaning bibens, at Clemson University

Oklahoma Wild Things--T. texanus?

Univ. of Nebraska--description of tribe Trichini, illustration of T. assimilis.

NCSU Entomology Collection lists four species from that state, with number pinned: affinis (188), piger (220), bibens (32), lunulatus (19). The same species are listed for Great Smoky Mountains National Park.

Beetles of Florida lists lunulatus, piger, rufobrunneus (Florida endemic), and affinis.

An Arizona checklist includes assimilis and piger.

Sikes Rhode Island lists affinis and piger.

Maine Forest Service collection includes affinis, assimilis and piger

Wisconsin has assimilis, piger and viridans