four-spotted sap beetle

not listed

NNR - Unranked

not listed

Four-spotted sap beetle, also called picnic beetle, is a common, small, sap-feeding beetle. It is native to North America. It occurs in the United States from Maine to northern Georgia, west to Washington and Oregon. It also occurs across southern Canada. It is common in Minnesota. It was introduced into Europe, where it was first found in 1948 in the area around Berlin, Germany. It has spread widely, and it now occurs from Ireland west to the Ural Mountains, from Scandinavia south to the Mediterranean Sea.

Four-spotted sap beetle adults are active from April through September. They feed on decaying fruit, corn, dung, carrion, tree sap, and fungi. They have been found in tree wounds and under the bark of cherry trees. Though called sap beetles, they feed mostly on fruit that is damaged, overripe, or rotting. They are attracted to all decaying matter that emits ethanol. Once attracted to damaged or decomposing fruits and vegetables, they will also attack intact fruits and vegetables in the vicinity. They are an agricultural pest when they invade stored or hanging fruit and vegetables. They are also a nuisance to people who are picnicking or consuming beverages outdoors. This has inspired two of the beetle’s common names, picnic beetle and beer bug.

Adults are black, shiny, and ⅛″ to ¼″ (4.0 to 7.0 mm) in length. The body is elongate-robust, oblong when viewed from above, and convex when viewed from the side or the front.

The head is large and broad. The antennae have 11 segments. The last three segments are abruptly expanded into a distinct, ball-shaped club. The mouthparts are directed forward.

The exoskeletal plate covering the thorax (pronotum) is wider than long. The margins are sharply and narrowly flattened and turned outward.

The hardened wing covers (elytra) are short. They are not grooved. They appear cut off at the end, and they do not cover the last two segments of the abdomen. There are four large, irregular, brownish-yellow spots, two near the front margin and two beyond the middle. This is the feature that gives the beetle its common name. The front spots are farther apart – farther from the inner margin (suture) – than the rear spots. On the front spots, the outline in deeply notched.

The last part of each leg (tarsus), corresponding to the foot, has five segments.

Total length: ⅛″ to ¼″ (4.0 to 7.0 mm)

The female deposits eggs near but not on decomposing plant material that is buried in the ground or in contact with the ground and the soil is moist.

Adults overwinter.

Decaying fruit, corn, dung, carrion, tree sap, and fungi

Sources

29, 30, 82, 83.

Common

Glischrochilus quadrisignatus four spotted sap beetle

Glischrochilus quadrisignatus, four spotted sap beetle, photographed on Barnes Prairie, Racine Co., WI on September 20, 2023.

Location: Barnes Prairie, Racine Co., WI

Glischrochilus quadrisignatus, four spotted sap beetle, photographed on Barnes Prairie, Racine Co., WI on September 20, 2023.