Bramble mason wasp

Conservation Status

IUCN Red List

not listed

NatureServe

NNR - Unranked

Minnesota

not listed

Description

Bramble mason wasp is a common, small to medium-sized, predatory, solitary wasp. It occurs in the United States east of the Great Plains, on the West Coast, and in the Rocky Mountains. It occurs across southern Canada. It is common and sometimes locally abundant in Minnesota. Adults are active from May through September in Minnesota, but they are most abundant in late summer.

Wasp size is often given in terms of the length of the forewing. The female has a ¼″ to ⅜″ (6.5 to 9.5 mm) forewing length. The body is black with extensive yellow markings.

The head is black. There are two large compound eyes, one on each side of the head, and three small simple eyes (ocelli) in a triangular pattern at the top of the head between the compound eyes. The inner margin of each compound eye is notched. The antennae are thread-like and have 12 segments, including a long first segment (scape) at the base, a short second segment (pedicel), and a whip-like section (flagellum) with 10 segments (flagellomeres). The upper side of all antennal segments is black and the underside is yellow. The last flagellomere is not hooked at the tip. The jaws (mandibles) are long and knife-like. The plate on the face (clypeus) is black with a yellow spot on each lateral margin and a pair of yellow spots on the lower margin. The spots usually merge on each side and often merge at the base. There is a yellow spot on the head between the antennae bases, a small yellow spot between the base of each antenna and the adjacent compound eye, and a small yellow spot behind each compound eye.

The thorax is black and has three segments, the prothorax, mesothorax, and metathorax. However, the first segment of the abdomen (propodeum) is fused to the thorax, giving the thorax the appearance of having four segments. Directly behind this, the second abdominal segment forms a petiole that connects the rest of the abdomen to the thorax.

The upper plate on the prothorax (pronotum) is short and collar-like. It does not have a narrow transverse ridge (carina) on the front margin. It extends rearward on the sides to the plate at the base of each wing (tegula). It appears horseshoe-shaped when viewed from above, triangular when viewed from the side. It is mostly black except for a yellow band on the front margin of the upper surface. The band tapers narrowly to each side, narrows toward the middle, and is sometimes narrowly interrupted in the middle.

On the mesothorax, the large front plate (mesoscutum) is entirely black and somewhat elongate. The tegulae are pointed at the rear. They are black in the middle with a yellow spot on the front and rear margins. The mesoscutum has two small projections at the rear corners called parategulae, a feature common to all potter or mason wasps (family Eumeninae). The parategulae are entirely black.

The smaller rear plate immediately behind it (scutellum) has a pair of well-developed yellow spots. On the upper surface of the metathorax (metanotum) there is an uninterrupted horizontal yellow band. The propodeum is entirely black. There is a large yellow spot on each side of the thorax below the wing bases. The first and second abdominal segments form a petiole that connect the abdomen to the thorax.

The rear part of the body (metasoma) has six visible segments. The upper part of the first segment of the metasoma (first tergite) is wider than long and only half as long as the second tergite. It is black with a yellow band at the rear. The second tergite has a broad yellow band at the rear and is almost as long as the remaining tergites combined. There is always a yellow band on at least the first through fourth tergites.

The wings are moderately tinted smoky brown and have dark veins. They are folded longitudinally over the body when at rest. On the forewing, the first discoidal cell is very long, about half the total length of the wing. There are three submarginal cells.

The legs are black and yellow. The second segment (trochanter) is not divided – it has just one segment. On each leg the third segment (femur) is mostly black, yellow just at the tip, and the fourth segment (tibia) is yellow above, black below. The tibiae on the middle legs have a single spur at the tip. The last part of each leg (tarsus), corresponding to the foot, has five segments. There is a pair of claws at the tip of each tarsus. The claws are split (cleft) at the end.

The male is smaller, with a 3⁄16″ to ¼″ (5.0 to 7.0 mm) forewing length. The antennae have 13 segments. The last flagellomere is hooked at the tip. The clypeus is entirely yellow. The spots on the scutellum are smaller and the band on the metanotum is usually absent. The abdomen has seven visible segments. There is always a yellow band on at least the first through fifth tergites.

Size

Female forewing length: ¼″ to ⅜″ (6.5 to 9.5 mm)

Male forewing length: 3⁄16″ to ¼″ (5.0 to 7.0 mm)

Similar Species

Habitat

Ecology

Season

May to September in Minnesota

Behavior

The wings are folded longitudinally over the body when at rest.

Life Cycle

The female nests in a preexisting cavity, which could be a boring in a twig, stem, or wood, an empty insect gall, or an abandoned mud dauber nest. The nest has multiple cells separated by a partition made of mud.

Larva Food/Hosts

Paralyzed caterpillars in the moth families Amphisbatidae, Oecophoridae, Gelechiidae, Tortricidae and Coleophoridae.

Adult Food

Distribution

Sources

24, 27, 30, 82, 83.

Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu. Accessed 6/19/2026).

Ancistrocerus adiabatus (de Saussure, 1853) in Bánki, O., Roskov, Y., Döring, M., Ower, G., Hernández Robles, D. R., Plata Corredor, C. A., Stjernegaard Jeppesen, T., Örn, A., Pape, T., Hobern, D., Garnett, S., Little, H., DeWalt, R. E., Miller, J., Orrell, T., Aalbu, R., Abbott, J., Abreu, C., Acero P, A., et al. (2026). Catalogue of Life (2026-05-15 XR). Catalogue of Life Foundation, Amsterdam, Netherlands. https://doi.org/10.48580/dgxsq. Accessed 6/19/2026).