260 bulletin united states geological survey. 



Ploas. 



The Oalifornian species which I have may be tabulated thus : 

 Halteres with a yellow knob: 



Wing-veins clouded with dark brown, but the inside of most of the 



cells hyaline — 1. fenestrata n. sp. 



Wings brown at base, which color gradually fades into grayish 

 posteriorly : 

 Thorax and proximal half of the abdomen clothed with yel- 

 lowish-rufous pile above and below 2. rufula n. sp. 



Whole body clothed with black pile, mixed with yellowish - 

 gray: 



Large species , 3. nigripennis Lw. 



Small species o . . . . 4. atratula Lw. 



Halteres with a brown knob : 



Abdomen metallic bluish-green : 



Abdomen opaque anteriorly and in the middle, its sides and 

 apex being shining bluish-green ; pile on thorax and on 



the upper side of abdomen rufous 5. obesula Lw. 



Abdomen shining greenish-blue ; pile on thorax and proximal 

 half of the abdomen above pale yellow ; on the distal 



half and below black 6. amahilis n. sp. 



Abdomen black 7. n. sp. indescr. 



None of the species described below has any marked impression on 

 the scutellum, and all have three submarginal cells. 



Ploas limbatalioew, Centur., viii, 51, from New Mexico, I do not know. 



1. Ploas fenestrata n. sp., ^ ?. — Wings dark brown along the an- 

 terior margin ; all the veins (except the seventh) and cross- veins broadly 

 clouded with brown. Hyaline spaces in the following cells : the two 

 outer submarginal and the distal half of the inner submarginal ; the end 

 of the first posterior; the three other posterior; the discal; the whole ax- 

 illary ; nearly the whole anal (except at both ends). A hyaline spot in the 

 distal half of the second basal cell. Head and thorax beset with long 

 black and shorter pale yellowish-gray pile, the latter thicker and longer 

 on the occiput, the chest, and the pleurae. Antennae black, with a very 

 stout first joint and an unusually elongated subcylindrical second joint 

 more than half as long as the first. Thoracic dorsum black, opaque ; 

 scutellum, when denuded, shining. Abdomen black, opaque ; on the 

 hind margin of each segment, a cross-band of whitish-gray recumbent 

 pubescence, which expands in the middle so as to coalesce with the pre- 

 ceding cross-band ; in the middle of each cross-band, on the hind mar- 

 gin of each segment, there is a more or less triangular spot of brownish- 

 fulvous hair ; these spots gradually diminish on each subsequent seg- 

 ment ; the whole abdomen is beset, besides, with black, erect pile. 

 Legs black in intact specimens, with a dense covering of brownish-ful- 



