1960] 
Evans — Bembix u-scripta 
47 
All of these features are unique or shared with only a very few 
other species of Bembix. Some of them, though unique in Bembix, 
are shared (at least in some measure) with species of the more primi- 
tive bembicine genus Stictiella ; these include characters I, 2, and 3 
above. Lohrmann (1948) has studied coloration in Bembix at some 
length, and has concluded that reduction in color pattern (i.e., less 
yellow) is correlated with structural advance; thus, on these grounds, 
character 9 should also be regarded as primitive. The remaining six 
characters should be regarded as specializations within the genus. 
However, those which involve the female (5, 6, 8) are not absolutely 
unique and the remainder (4, 7, 10) involve male secondary sexual 
characters, which are remarkably plastic in the bembicine wasps. 1 he 
more striking features thus suggest that these wasps do, in fact, retain 
several features which may have been characteristic of the ancestral 
Bembix , though obviously an assortment of specializations of a less 
striking sort have been acquired. 
In describing Bembix arcuata, Parker (1917) listed the following 
characters by which it differed from u-scripta (Fox 1895) : 
1. The nature of the male “genital stipes” (i.e., parameres), 
which are much more slender and attenuate than in •. u-scripta . 
2. Mesosternum marked with black (yellow in u-scripta) . 
3. Abdominal sternites 2-4 with small lateral yellow spots (in 
u-scripta these are more extensively yellow and there is some yellow 
on the sternites behind these). 
4. Apical sternite black (yellow in u-scripta ). 
Since the first of these characters involves an important structural 
distinction, it should be considered first. Parker based his interpreta- 
tion of u-scripta on the type specimen, one other male, and four fe- 
males. I have examined these two males and find that it is true that 
the parameres are less attenuate than in the type of arcuata — or in 
males from both colonies studied. However, the difference is slight 
and relative, and I cannot agree with Parker that the genitalia “differ 
widely”. Parker’s figures tend to exaggerate the differences between 
the two: yet the differences cannot be entirely reasoned away. 
Study of the color characters supposed to separate these species re- 
veals that while they may apply to the type specimens, they are by no 
means absolute when additional specimens are considered. The type of 
u-scripta is almost wholly yellow, that of arcuata predominantly black. 
Specimens from the Texas colony which I studied are close to arcuata , 
but exhibit enough variation to cause confusion in using Parker’s key. 
