Reprinted from: Snelling, R. 1970. STUDIES ON NORTH AMERICAN BEES OF THE GENUS
HYLAEUS. 5. THE SUBGENERA HYLAEUS. S. STR. AND
PARAPROSOPIS (HYMENOPTERA: COLLETIDAE) Contributions in Science, No. 180.|
This common California species is closely related to H. wooton; and
females are apt to be very difficult to separate in the absence of males. The
two species are largely allopatric with overlaps occurring only in some areas
of southern California and along the western portions of the Sierra Nevada.
Females of H. polifolii which possess the preapical clypeal macula are easily
recognized; I have never seen specimens of H. wootoni so maculated. The
population of H. polifolii present on Santa Catalina Island, Los Angeles Co.,
Calif., was given a varietal name by Cockerell; in the females of this population,
the clypeal macula seems always to be present. Populations from mainland
California mayor may not have a maculate clypeus, but this feature is
subject to much variation within a given sample and is, moreover, not correlated
with distribution. I see nothing to be gained by recognition of this
insular form and have synonymized it under the nominate form.
The facial maculae of the males, too, are subject to considerable variation.
In what I consider to be the basic or "typical" pattern, the clypeus is
entirely yellow, the supraclypeal area is black, and the lateral face marks
terminate above at a point about equal to a socket diameter above the antennal
sockets. One variant form, very rare, exhibits an obscure maculation of variable
size on the supraclypeal area. In the second variant form, which is fairly
common, the clypeus becomes darkened along the lateral margins; this infuscation
frequently encroaches so extensively onto the clypeus that the
maculation is reduced to an erect median stripe.