48 PROCEEDINGS OF THE NATIONAL MUSEUM. vol* 52. 



fasciae on tergites 1-6, first with a deep rectangular emargination at an- 

 terior middle and three slight emarginations on posterior border, second 

 with &n elliptical black spot near the middle on either side the median 

 line and three slight posterior emarginations, third similar to second, 

 but with two black spots narrowly united to an anterior medial emar- 

 gination, fourth and fifth on anterior margin dorsally biemarginate 

 and laterally waved, ultimate tergite except narrow anterior border, 

 first and second sternites entirely, third entirely or with only a cen- 

 tral anterior black spot, fourth and fifth with rather broad fasciae 

 narrowed medially and laterally, ultimate sternite apically, coxae, 

 trochanters except spot above, femora except stripe above, tibiae 

 except sometimes a stripe below, and tarsi, lemon yellow. 



Length. — 16-18 mm. 



The flagellum in both sexes is slender, and the apical half is tes- 

 taceous below. In the male the apical half is carinate on the pos- 

 terior side and the ultimate segment curved. The intermediate 

 femora of the male are smooth beneath and the metatarsus not 

 curved. The second sternite is nontuberculate and the eighth is 

 without a discal spine. In color and markings the sexes are remark- 

 ably similar and the different specimens show but little variation 

 from the typical form. On the first tergite the emargination may 

 appear as an anterior rectangular black spot or it may be connected 

 with the posterior emargination so as to cut off a pair of posterior 

 median yellow spots or a single yellow spot. On the second on both 

 male and female we usually find a single median black spot that 

 may or may not be connected by a narrow medial emargination 

 with the anterior black border. Other slight modifications may 

 occur but the basic pattern remains the same, the variations being 

 due to a greater or less extension of the black on the dorsal surface. 

 The lateral borders of the ultimate tergite of the female, especially 

 toward the base, are provided with numerous stout spines. The 

 wings are hyaline and relatively long; the pubescence short and 

 sparse, and the labrum, clypeus, and anterior orbits of the female show 

 a silvery reflection when viewed at the proper angle. In his descrip- 

 tion of this species Fox associated as male and female of the species 

 a male that I regard as representative of a different species entirely. 

 I base this judgment on the fact that males I have before me and 

 the female of Fox's tenuicornis are so similar that they can be dis- 

 tinguished only by their sexual characteristics, whereas the male 

 Fox assigned to this species differs from the female not only in color 

 and widely in the pattern of the markings, bit also in having the 

 head narrower than the thorax. I have accordingly considered the 

 male as representative of a new species and have redescribed it 

 herein under the name bituberculata. 



Habitat. — California, Arizona, Texas. 



Number of specimens examined — Males, 3 ; females, 7. 



