Although the species of Ophiogomphus are well defined in the adult stage their nymphs are extremely uniform in structure and are difficult to separate. This is perhaps not remarkable in view of the similarity of their habitats, all the species being shallow burrowers in running streams, usually clear, with a sandy or pebbly bottom, where they occupy the edges of currents, gentle riffles, or pools at the foot of rapids.

Length 5.7 to 6.1 mm., width 1.65 to 1.75 mm. Form narrow, parallel, color piceous bronzed, base of antennae, prosternal lobe and legs reddish, surface moderately shining, distinctly pale pubescent.

In size, form, color and all other details except as mentioned below, this species is so similar to the common quercinus as to be practically indistinguishable to the casual eye.

♀ (Type). Length about 4 mm.; head broad and short, with very wide face; clypeus and labrium entirely black, as also supraclypeal area; lateral face-marks present, pale yellow, long and very narrow, a little broadened below. The upper end, on orbit, a little above level of antennae; mandibles yellowish-white with the apical part broadly ferruginous; scape slender, yellow in front; flagellum thick black, the under side pale yellowish; front and vertex shining, dark olive green; thorax shining dark green, the mesothorax and scutellum very brilliant, mesothorax with thin erect white hair; tubercles, a slender line along sides of mesothorax above base of wings, and a short stripe at each side on upper border of prothorax, all pale yellow; wings clear hyaline, nervures practically colorless ; stigma large, hyaline, with a dusky border ; hind legs black, except that the femora are yellow beneath; middle legs with the femora broadly yellow at apex and the tibiae yellow in front; front legs similarly colored, the tihiae very broadly pale yellow; anterior and middle basitarsi pale yellow and the small joints reddish, but hind tarsi black; abdomen shining, dorsally dark, slightly brownish, the first tergite with only a very small yellow mark at each side; tergites 2 to 4 with successively broader pale yellow bands, having a linear interruption in middle; fifth tergite broadly yellowish on each side; apical plate pale reddish; venter light yellow.

In collections made by the writer during the last few years the following new forms have appeared, the types of which are in his collection.

Isoperla fumosa sp. nov.

Adult. Head brown, yellow around eyes and bases of antennae, a yellow spot in the ocellar triangle and another in front of the anterior ocellus; antennae and palpi brownish. Prothorax with angles somewhat rounded, brown with darker rugosities on either side of the broad central yellow stripe. The latter has a narrow brown central line. Wing veins brown. Legs brown. Abdomen brown with a little pale colour at the base and a pair of dorsal yellow dots on most of the segments. These dots are sometimes nearly obscured. Cerci dark brown at base, paler beyond.

Holotype male. Piceous, shining, form of arizonensis but slightly smaller. Clypeus narrowly emarginate and notched at centre of apex, head in front and on sides coarsely punctate; smooth behind, genae acute, prominent, coarsely and rather densely punctate; frontal horn long, arcuate, surface deeply pitted on sides and rear, front smooth. Thorax with a median protuberance triangularly emarginate at apex, the angles rounded and convergently apically; surface of protuberance slightly flattened, with distinct longitudinal impression, very coarsely and rather sparsely punctured at the centre; at each side near side margin a horn-like projection, the surface between these and the median protuberance deeply excavated and coarsely but rather sparsely punctate; between the usual short carina near the side margin and the horn-like projection is at about the middle a shallow fovea which is very coarsely punctured, surface of thorax coarsely punctate at margins, near front angles, and as noted above, the disc very finely and sparsely punctured; front angles obtusely subangulate, lateral margin near the front angles not sinuate, hind angles broadly rounded; fore part of thorax not tuberculate.

While studying some material sent to me from the southern part of Caliicrnia, there came to my notice this very small species of bark beetle, which interested me greatly. While it is not of much economic importance, as are other members of the subfamily Hylesininae, it is of interest because of its host relationship to Chaetophloeus hystrix (Lec.). Both occur on Rhus integrifolia.

This is a new species and a description of the same follows.