Extracted from: Snelling R.R., (1983). The North American Species of the Bee Genus Lithurge (Hymenoptera: Megachilidae). Contributioun in Science, number 343, pp. 1-11. The Natural History of Los Angeles County, 1983
Females provision the cells with pollen from species of Opuntia, but both sexes have been taken at flowers of other genera. Hurd (1979) recorded this species on flowers oTEchi-nocactus, Encelia californica, Eriogonum, and Sphaeralcea. Previously unpublished floral records include: Agave neva-densis, Argemone platyceros, Argemone sp., Asclepias erosa, Baileya multiradiata, Cirsium californicum, Cirsium sp., Calochortus concolor, Chilopsis linearis, Cleome serrulata, Cnicus sp., Grindelia squarrosa, Prosopis juliflora, Robinia neomexicana, Senecio longilobus, Verbena stricta, Verbesina encelioides, and "sweet pea."
For many years, L. apicalis has been divided into two sub-species: L. a. apicalis and L. a. opuntiae. The former, with ferruginous hairs on the last tergum of the female, is a northŽern form, found in South Dakota, Wyoming, Nebraska, KanŽsas, Colorado, Utah, and Nevada. The southern population, L. a. opuntiae, with dark brown hairs on the last tergum of the female, ranges from New Mexico to southern California. Both forms, however, occur in New Mexico, Arizona, and California. In many areas the two occur together, along with many specimens of intermediate character
In view of the broad zone of intergradation, were mixing of the forms occurs and which actually includes much of the range of L. a. opuntiae, it hardly seems desirable to separate the two forms nomenclatorially. Accordingly, L. a. opuntiae its here treated as a synonym of L. apicalis.
Cockerell (1937) described L. arizonensis from two feŽmales collected in the Baboquivari Mountains of Arizona. These were said to differ from L. a. opuntiae by their more flattened and coarsely punctate clypeus and by the deeper, sparser facial punctures. I have examined the type of L. arizonensis (in the CAS) and find no significant differences between this specimen and other individuals of L. apicaiis. All the differences cited by Cockerell fall well within the range of character variation that I attribute to this species.
The male from Port Isabel, Texas, described by Cockerell (1917) as L. apicaiis subsp. littoralis, is a distinct species and a senior synonym of L. bruesi (see below).