_Butterfly._--On the upper side uniformly brown. On the under side dark, with a narrow submarginal and an irregular median transverse band, and a pale short bar closing the cell on both wings; a black spot at the anal angle of the secondaries, preceded by a few bluish-green scales. Expanse, 1.00-1.10 inch. _Early Stages._--Unknown. Habitat, California and Utah. (17) =Thecla sæpium=, Boisduval, Plate XXIX, Fig. 33, ♂; Fig. 34, ♀ (The Hedge-row Hair-streak). _Butterfly._--Almost identically like the preceding species, except that the wings on the upper side are a trifle redder, on the under side paler; the lines on the under side of the wings are narrowly defined externally by white, and the anal spots are better developed and defined on the hind wings. Expanse, 1.20 inch. _Early Stages._--Unknown. This species is found throughout the Pacific States, and I am inclined to believe it identical with _chalcis_. If this should be proved to be true the latter name will sink as a synonym. (18) =Thecla adenostomatis=, Henry Edwards, Plate XXIX, Fig. 25, ♂ (The Gray Hair-streak). _Butterfly._--Mouse-gray on the upper side, with a few white lines on the outer margin near the anal angle; hoary-gray on the under side, darker on the median and basal areas. The limbal area is defined inwardly by a fine white line, is paler than the rest of the wing, and on the secondaries is marked by a full, regularly curved submarginal series of small dark lunules. Expanse, 1.30 inch. _Early Stages._--Undescribed. Habitat, California. (19) =Thecla spinetorum=, Boisduval, Plate XXIX, Fig. 21, ♀ (The Thicket Hair-streak). _Butterfly._--Dark blackish on the upper side, with both wings at the base shot with bluish-green. On the under side the wings are pale reddish-brown, marked much as in the following species, but the lines and spots are broader, more distinct, and conspicuous. Expanse, 1.15 inch. _Early Stages._--This species is reported, so far, from Colorado, California, and Washington. (20) =Thecla nelsoni=, Boisduval, Plate XXX, Fig. 8, ♀, _under side_; Fig. 13, ♀ (Nelson's Hair-streak). _Butterfly._--Bright fulvous on the upper side, with the costa, the outer margins, the base, and the veins of both fore and hind wings fuscous. On the under side the wings are paler red, with an incomplete narrow white line shaded with deep red just beyond the median area, and not reaching the inner margin. This line is repeated on the hind wing as an irregularly curved median line. Between it and the outer margin on this wing are a few dark lunules near the anal angle. Expanse, 1.00 inch. _Early Stages._--I cannot discover any account of these. The species has been found in California and Colorado. (21) =Thecla blenina=, Hewitson, Plate XXX, Fig. 9, ♂, _under side_ (Hewitson's Hair-streak).