6o8 CALIFORNIA ACADEMY OF SCIENCES. 



by Gray in Griffith's Animal Kingdom, then the present 

 species is entirely different from Pt. mtsella. 



It may be recognized by the following characters: En- 

 tirely black, except the irregular posterior half of abdo- 

 men, the venter, the front legs, and the tibite and tarsi of 

 the middle and hind legs. The venter and the light por- 

 tions of legs are yellowish, the front femora being dark 

 basally. The posterior portions of abdomen are orange- 

 3'ellow, being the sides of second segment, and all of 

 third, fourth and fifth (anal) segments except a median 

 black stripe on third, which is much widened anteriorly 

 where it joins the black of anterior portions and less 

 widened posteriori}^ and a median black spot at base of 

 fifth. In the red of sides of second segment there is a 

 triangular black spot, whose edge is identical with poste- 

 rior border of the segment. 



The head is hemispherical, mostly taken up with the 

 contiguous eyes, which are very pilose. The costal dil- 

 atation of wing is very pronounced and obtuse or swollen 

 in outline, wdth the short but stout tooth on the outer pos- 

 terior border of swelling. The tegula? are smok}^, with 

 a blackish narrow border. Wings hyaline ; wing -veins 

 yellowish, brownish basally. 



28. EuLONCHUS TRiSTis Locw. California. One 

 specimen. Abdomen more greenish than violaceous. 



29. Oncodes ^don n. sp. 



Baja Purisima, Lower California. April. One spec- 

 imen. Length, slightly more than 4 mm. 



Very similar to Oncodes humeral is O. Sack. (Biol. 

 Centr.-Am., Dipt., i, 164-5), but differs in the tegula? 

 beino: fuscous whitish with a well-defined narrow dark 

 brown margin. Wings without apical brownish tinge. 



Humeral and prescutellar callosities, and upper pleurae. 



