4 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



Not so ; scutellum less produced, the yellow marks or 

 band on scutellum not in a straight line 5. 



2. Band on second abdominal segment nearly as widely 



interrupted as that on first, i. e., reduced to lateral 



marks (Europe) strigatum (Panzer). 



Band on first adbdominal segment reduced to lateral 

 marks, but that on second at most very narrowly in- 

 terrupted 3. 



3. Hind tibia without black (New Mexico) . . . .gilense (Ckll.) 

 Hind tibia mth a good deal of black 4. 



4. End of male abdomen with four little teeth; band on 



second abdominal segment very broadly interrupted 



(Mojave Desert ehrhomi (Ckll.) 



End of male abdomen without such teeth : band on sec- 

 ond abdominal segment very narrowly interrupted 

 (Southern California) robertsoni (Ckll.) 



5. Yellow band on first abdominal segment broadly inter- 



rupted in the middle (New Mexico) . . . .perpictum (Ckll.) 

 Band on first abdominal segment entire in the middle, 

 interrupted, if at all, at the sides 6. 



6. Base of abdomen with a good deal of red (Georgia, 



Texas, New Mexico, etc curvatum (Smith.) 



Base of abdomen without red 7. 



7. End of male abdomen strongly trilobed; male with no 



supraclypeal mark; markings of abdomen chrome yel- 

 low in both sexes (So. California) consimile (Ashm.) 



End of male abdomen truncate, faintly trilobed; male 

 with a small supra ch^^eal mark 8. 



8. Markings of abdomen pale yellow, bands more incised 



laterally (New Mexico, Colorado) parvum (Cress.) 



Markings of abdomen bright yellow, bands less incised 



laterally (Southern California) davidsoni (Ckll.) 



Dianthidiiim robertsoni, n. sp. 



Four specimens collected by. Dr. Davidson, three from Rock 

 Creek, one from Los Angeles. Named after Mr. Charles Rob- 

 ertson, who first pointed out the presence of pulvilli in the 

 genus. Small and compact, 5% to 7 mm. long, the larger being 

 females; black, with chrome yellow markings, (Strongly punc- 

 tured; apex and apical half of costa of wings broadly fuligin- 

 ous, the whole of the marginal and nearly all of the submar- 

 ginal cells dark; the only yellow marks on head in the female 

 are the large cuneiform lateral face-marks, and the entire occi- 

 pital band, but in the male the clypeus and two triangles occu- 

 pying the corners of the supraclypeal area and touching or al- 

 m.ost touching medially are light yellow; markings of thorax 

 and abdomen as in D. gilense, except that the anterolateral 



