ART. 4. REVISION OF THE FAMILY THEREVIDAE—COLE. V7 
yellowish white pile at the base and white beyond, the anal segment 
long white haired. The wings are hyaline with a large black stigma. 
Type locality —Hot Springs, Arizona, June 20.| 
Type.—In the United States National Museum, Cat. No. 26021. 
PSILOCEPHALA PLATYPTERA Krober. 
1914, Psilocephala platyptera Kroser, Beiheft z. Jahrb. Hamb. Wiss. Anstalten, 
vol. 31, p. 47. 
Male.—Length8 mm. The most beautiful and extraordinary The- 
revid of Central America; perhaps the representative of a new genus. 
The head is almost round and is silver white pilose, the antennae 
and mouth parts light reddish yellow, the bristles delicate, black. 
The mesonotum, scutellum, pleura, and coxae are pure silver white. 
The abdomen is silvery, the second segment with deep black lateral 
triangles, the third with a deep black cross band. The venter is black. 
The legs and halteres are blackish brown. The wings are hyaline, 
longer than the abdomen and broad; the whole wing tip is dark satin 
brown with a small cross band in the fourth posterior cell and one 
beginning on the stigma and running to the anal cell. 
Type locality —Rockstone Essequebo, Guatemala. 
Type.—In the United States National Museum, Cat. No. 26022. 
PSILOCEPHALA NIGRINA Krober. 
1914. Psilocephala nigrina KrosER, Beiheft z. Jahrb. Hamb. Wiss. Anstalten, 
vol. 31, p. 53. 
Female.—Length 7mm. Very near P. munda, but the frontal cal- 
losity is rounded out and smooth and a black stripe runs from it to 
the antennae. The antennae are black, very robust, especially the 
third joint, which appears pear-shaped, with a short, thick style. 
The halteres are deep black. The legs are black, the tibiae and 
metatarsi dusty brown. The abdomen is shining black, the second 
and third segemnts with small silver side spots on the posterior mar- 
gins, the fifth segment with a wide band. The wings are brownish, 
almost blackish tinged. 
Type locality.—Florissant, Colorado, June 14. 
Type.—tIn the United States National Museum, Cat. No. 26023. 
PSILOCEPHALA LACTEIPENNIS Kréber. 
1914. Psilosephala lacteipennis Kroser, Beiheft z. Jahrb. Hamb. Wiss. Anstal- 
ten, vol. 31, p. 53. 
Male.—Length 6mm. A very beautiful, characteristic species. 
The head is silvery white, shining, only the frontal triangle velvet 
black. The antennae are slender, black. The pile is rather delicate, 
snow white. The mesonotum is dull, pale gray, with a broad, deep 
black stripe from the wing base to the shoulder. There is a delicate 
