small carpenter bees

Zadontomerus is a subgenus of small carpenter bees. It occurs in North America and Central America. There are 31 Zadontomerus species worldwide, 20 species in North America north of Mexico, and at least 3 species in Minnesota.

Zadontomerus are solitary bees. They build their nests in pithy twigs of woody plants in many plant families, including in sumac, honeysuckle, and raspberry. All are generalist feeders, gathering nectar from a wide variety of flowers from at least 33 plant families.

Most Zadontomerus bees collect pollen from a variety of flowers to provision their nests. Only one species, Ceratina sequoiae, is believed to provision its nest exclusively with pollen from flowers in the genus Clarkia, though it visits many flowers for nectar.

Zadontomerus are small black, metallic blue, or metallic bluish-green bees.

The cheeks (genae) and the area on the sides of the face parallel to the eye (paraocular area) have distinct pits (punctures). The feeler-like structures on the under jaws (maxillary palps) have six segments. The ridge in front of the simple eyes (preoccipital ridge) is distinctly keeled. On the female, the jaw (mandible) has three teeth. On the male it has two teeth.

The collar on the plate covering the first segment of the thorax (pronotum) has a transverse ridge in the middle and is rounded on the sides.

The upper side of abdominal segments two through five (T2 to T5) each have a dark transverse line (gradulus) formed by a groove between two regions of the segment. The underside of segments two and three (S2 and S3) also have graduli. On the male T6 has a dense tuft of hairs in the middle, and T7 has a flat projection at the tip.

On the front and middle legs, the fourth segment (tibia) has a single, small spur at the tip.

Three Ceratina species occur in Minnesota. All three are in the subgenus Zadontomerus and are very similar in appearance. On Ceratina calcarata males the third segment (femur) on the hind leg is expanded and there is a triangular projection in the middle. On Ceratina dupla males, the hind femur is also expanded but there is no triangular projection in the middle. Unfortunately, this feature is not visible in most photos. Identifying females to species level is much more difficult. Identification from photos often stops at the level of this group of three.

Sources

4, 24, 27, 29, 30, 82, 83.

This subgenus has no common name. The common name of the genus Ceratina is small carpenter bees, and it is applied here for convenience.

Location: Albany, NY

Location: Woodbury, MN