splendid earth-boring beetle

not listed

NR - Unranked

not listed

Splendid earth-boring beetle is a medium-sized scarab beetle. It is one of the most common and most widely distributed species in the genus.

Adults are ½″ to ¾″ long and ¼″ to ½″ wide. The body is very stout, oval when viewed from above (dorsally) and strongly convex when viewed from the side (laterally). It is shiny and usually bright metallic green, purple, or bronze, sometimes light blue.

The first segment of the thorax is large and is covered above by a metallic green exoskeletal plate (pronotum). The pronotum is coarsely and unevenly pitted (punctate).

The hardened outer forewings (elytra) are free, not fused; ridged longitudinally (striate); and pitted in rows. The pits are shallow but well developed. The elytral margins are narrowly flared. The innermost grooves (stria), where the elytra meet in the middle, do not extend to the base of the elytra. The color of the stria is the same as the color of the rest of the elytra. There is a small, metallic green, triangular plate (scutellum) between the bases of the wings that is not covered by the elytra. The sides of the scutellum are only slightly curved.

The head is large and is not concealed beneath the pronotum. The antennae are dark reddish-brown and clubbed. They have 11 segments. When viewed from above the base of the antennae are not visible. The last three segments are light reddish-brown and are expanded sideways on one side into long flattened lobes. The antennal lobes can be closed into a tight club or fanned out to detect odors. They are small and both sides are straight, not convex.

The legs are stout and black with a slight bluish or greenish iridescence on the upper surface of the third and largest leg segment (femur). The fourth segment (tibia) of the front leg of the male is enlarged, broad, and adapted for digging. The tibia of the middle and hind legs have a distinct horizontal ridge. The end segment of each leg (tarsus) has 5 sections.

There are two recognized subspecies. G. s. miarophagus is larger, ⅝″ to ¾″ long and ⅜″ to ½″ wide, coppery green to purplish-black, and is found generally west of the Appalachian Mountains. G. s. splendidus is smaller, ½″ to 11 ⁄16″ long and ¼″ to 7 ⁄16″ wide, bright green or occasionally light blue,rarely purplish-black, and is found generally east of the Appalachian Mountains. They are otherwise identical in appearance.

Total length: ½″ to ¾″

One generation: March to November

Adults are active at night.

In September and October, new male adults emerge about a week before the females. They feed mostly on fungi. During this time, the male creates a burrow 5 to 8 inches deep into the soil under decaying fungi. He provisions it with the decaying fungi, feeds in the burrow, and waits for a female. Copulation takes place inside the burrow. Before or after breeding, a 2½″ to 3½″ long, 1″ in diameter food cell is excavated. The food cell is then tightly packed with concentric layers of pieces of dead leaves. The adult male and female overwinter in the burrow, emerging the following April. From April through June the female deposits yellowish-white eggs in the food cell. The larvae pass through three stages of development (instars) before pupating.

The preferred food is fungi, but adults have also been seen feeding on carrion, dung, and feathers.

Sources

24, 27, 29, 30, 82.

Common and widespread in eastern and midwestern United States

Almost all sources of information for this species, including BugGuide.net, refer to this species by the scientific name Geotrupes splendidus. The usually reliable ITIS, originally referred to as Interagency Taxonomic Information System, now just ITIS, lists this species as Geotrupes splendidulus. A very few other sources also use this spelling. It is not known whether this is a misspelling that got picked up by a (very) few authors, or a legitimate synonym. However, Geotrupes splendidulus is never listed as a synonym for Geotrupes splendidus.

Geotrupes splendidus splendid earth-boring beetle

Geotrupes splendidus, splendid earth-boring beetle, photographed at Barnes Prairie, Racine Co. WI on Oct. 2, 2023.

5 miles from Dent, MN near Dead Lake

Location: Barnes Prairie, Racine Co., WI

Geotrupes splendidus, splendid earth-boring beetle, photographed at Barnes Prairie, Racine Co. WI on Oct. 2, 2023.

Location: Ottertail County, MN

5 miles from Dent, MN near Dead Lake

Location: Lake Shore, MN