100 AMERICAN DIPTKRA, 



ff i^iTiCxtvv' (W M go litorea Aldi-ich, n. sp. 



Length 1.9 mm. ; of wing, about the same. 



Ground color of body black, bristles all black. 



Head yellow, the occiput, vertex and middle of face black ; epistoma bordered 

 with a narrow black line, which expands upward between the vibris.=al ridges; 

 vibrissse of moderate size; antennae yellow, the third joint considerably infus- 

 cated and slightly elongate; arista short, black, a little thickened at base; front 

 yellow, the sides narrowly cinereous and the vertex black in color, which does 

 not extend forward in a sharp angle as usual ; two large fronto-orbital bristles — 

 but the posterior one missing on one side in the described specimen, seemingly 

 an abnormality. Eyes roundish, slightly angulated above, the cheeks over one- 

 third as high as the eyes. Palpi rather brownish-yellow. 



Thorax cinereous, with black ground color, the pleurte, scutellum and metano- 

 tum concolorous ; bristles large and hairs very few ; between the rows of dorso-cen- 

 trals are about ten hairs arranged in two rows, very distinct ; scutellum with two 

 pairs of bristles, otherwise bare; mesopleura with one bristle and several hairs at 

 the posterior edge, just below the base of the wing; pteropleura bare; sterno- 

 pleura with two bristles and a few hairs ; halteres light yellow. 



Abdomen cinereous, concolorous with thorax; hypopygium small, with some 

 indistinct grasping organs turned forward underneath. 



CoxsE and femora blackish, tibife and tarsi yellow, the latter but little infus- 

 ca ted towards the tip ; pulvilli moderately large. 



Wings almost hyaline, the veins yellowish, cross-veins not infuscated ; third 

 vein ending precisely in the apex; bristles of the costa small and few. 



One male. Aldrich : Pacific Grove, California, May 8, 1906, 

 collected at the seashore a little above high tide line, where a small 

 seepage of fresh water made a streak of verdure. 



Explanation of Plate IV. 

 The parts are variously magnified : No. 1 is one of the smallest 

 of the family; No. 3 above the average. The veins of the wings 

 are not generally very black in life, making the actual appearance 

 quite different from the drawing; this is especially true of No. 7. 



Fig. 1. — Siligo oregona, new genus and species. 



'" 2. — Porsenus johnsoni. new genus and species. 



" 3. — Eccopfomera americana, new species. 



" 4. — Anorostoma maculata, new species. 



" 5. — Anorostoma maculata, new species. 



" 6. — Helomyza limbata, Thomson. 



" 7. — Siligo oregona, new genus and species. 



" 8. — Cyrtonotnm helvitm, Ijoew. 



" 9. — Oyrtonotnm helcuin, Loew. 



Figs. 8 and 9 are added for comparison, but the species does not 

 belong to this family. The second basal cell is confluent with the 

 discal, as figured, in many cases, but is sometimes distinct; the sec- 

 ond and third basals are very small. The anterior fronto-orbital 

 curves strongly forward. 



