Images and text by Hartmut Wisch, RSABG Volunteer 

Pollen Wasps are unique among vespids (members of the hymenopteran family, Vespidae) in that they provision their nest cells with pollen and nectar rather than with other insects or spiders. Females are solitary nesters, and build cylindrical cells mostly on rocks (or plants, at least in Pseudomasaris vespoides) using soil mixed with nectar or water.  They are active mostly during early spring and summer when their preferred plants are in flower.  Depending on species they favor flowers, mostly of Phacelia, Eriodictyon (both in Boraginaceae, formerly in Hydrophyllaceae), or Penstemon (Veronicaceae, formerly in Scrophulariaceae), and are thought to be major pollinators of those plants.

Males frequent areas where females gather pollen and nectar, or at nesting sites. Of the fifteen species of Pseudomasaris, a genus unique to Western North America (except for a single record from southern Ontario, Canada), ten occur in California.  At least three species frequent the San Gabriel foothills. The genus Pseudomasaris is classified in the vespid subfamily Masarinae, all of which have clavate (clublike at the tip) antennae.  The antennae of males in Pseudomasaris are generally longer than those of females, and have expanded terminal segments.  Masarine wasps are found mostly in arid to semi-arid climates of the world.

Female Pseudomasaris coquilletti gathering pollen in Phacelia flowers

Female P. coquilletti taking nectar in Phacelia

Male P. coquilletti nectaring in Phacelia

Pseudomasaris edwardsii, female, in Phacelia

P. edwardsii, male, taking nectar in Phacelia

Male P. vespoides

Male P. vespoides in Penstemon spectabilis flower

Female P. vespoides in Penstemon spectabilis

Female P. vespoides in Penstemon spectabilis

Recommended reading:
                           
Gess, Sarah K. 1996. The Pollen Wasps - Ecology and Natural History of the Masarinae.  Harvard University Press

Richards, O.W. 1963. The species of Pseudomasaris Ashmead (Hymenoptera, Masaridae). University of California Publications in Entomology, 27: 283–304, 3 plates.

Richards, O.W. (1966): New records of Pseudomasaris Ashmead (Hymenoptera: Vespoidea, Masaridae), with notes on P. phaceliae Rohwer and P. cazieri R.M. Bohart. Proceedings of the Royal Entomological Society of London (B) 35: 47-55.

Torchio, P.F. 1970. The ethology of the wasp, Pseudomasaris edwardsii (Cresson), and a description of its immature forms (Hymenoptera: Vespoidea, Masaridae). Contributions in Science, 202. 32 pp.

Torchio, Philip F. 1974.  Mechanisms Involved in the Pollination of Penstemon Visited by the Masarid Wasp, Pseudomasaris vespoides (Cresson) (Hymenoptera: Vespoidea).  Pan-Pacific Entomologist 50: 226-234.