Heteroecus sanctae-clarae

GALL. — A smooth, two-parted gall. The lower portion of the gall is rather cylindrical, narrower apically where it is inserted into the second part, concave basally where it is attached to the twig; the upper portion is low, cylindrical, as wide or more often nearer twice as wide as the lower portion, as high or little higher than the low^er portion, drawn more or less abruptly into a long, rather slender, blunt point; gall measuring up to 15. mm. in greatest diameter, and 20. mm. in total length; externally smooth or slightly roughened, covered with a bluish white bloom when fresh, becoming light buff to golden yellow, blackening on weathering. Internally compact, not woody, solid except for a small, irregular cavity in the upper portion ; the larval cell about central, divided between the two parts of the gall, or nearer the base. Sessil on twigs of Quercus chrysolepis.

RANGE. — California: San Jacinto Mountains to Dunsmuir.

This is not an acorn gall, as stated in the original description, but a bud gall. The insect shows extremely close relationships to other species of the genus. Indeed, the distinctive characters of the species are few. These characters are not as marked as for most varieties of species of the genus, and but for the character of the gall, sanctae-clarae would never have been described when it was. In regard to the gall, the character of the external surface, the compact internal tissues, and the fact that it is a monothalamous bud gall would indicate even a physiology related to that of the other species. It is in general form only that the galls are distinct.

[Kinsey describes three varieties which do not vary in gall morphology; see paper for details]

- Alfred Charles Kinsey: (1922) Studies of some new and described Cynipidae (Hymenoptera)^©

Reference: https://www.biodiversitylibrary.org/page/45387508#page/158/mode/1up