1977] 
Porter — Mesostenines 
47 
PHAENOLOGY: March to May in Valley; flies from March to 
November elsewhere in southern part of its range and from late 
May to mid-October farther north. 
13. Mesostenus opuntiae n. sp. 
(Fig. 2) 
Holotype: female, USA (Texas: Hidalgo County, Valley Bo- 
tanical Garden at McAllen, 10 I ’76, C. C. Porter). (Townes). 
FEMALE: Color: scape black with a little dull brown below; pedi- 
cel black with dull brown on apex; flagellum black with a little 
pale brown on base of first segment and a ventrally interrupted 
white band on segments 6-11; palpi brownish white; mandible white 
on basal half with apical half grading through pale brown into 
black on teeth; head mostly white on clypeus, cheek, face, and on 
a broad, uninterrupted orbital band, which progressively widens 
rearward and below to cover much of temple, as well as with pale 
brownish on mandibular condyles, hypostomal carina, medio-dor- 
sal margin of clypeus, slightly on apical face and apical margin of 
clypeus, and on antennal sockets, and with black broadly and ir- 
regularly along lateral and dorso-lateral margin of clypeus, irregu- 
larly around antennal sockets below, on about median half of front 
and vertex, more broadly on occiput and post-occiput, and then 
increasingly more narrowly ventrad on temple along occipital carina 
to about its lower 1/5; pronotum black basally with fulvous on 
apical half that grades into dull white on apical margin; pronotum 
black with a broad white band on most of front margin and on all 
but about median 1 / 5 of dorsal margin; mesoscutum black with a 
median white blotch located between apices of notauli and with 
white on pre-scutellar ridge; scutellum black, broadly margined with 
white laterally and behind; postscutellum mostly white; meso and 
metanotal axillary troughs black with hind rims narrowly whitish; 
mesosoma otherwise fulvous with white on tegula, subalarum, 
broadly on about upper 4/5 of front margin of mesepisternum, 
toward dorsum of mesepimeron, dully in lower hind corner of 
mesepisternum, and dully on apex of lower metapleuron, as well 
as with black above, below and behind subalarum, on most of 
prepectus, on most of apex of metasternum in front of mid coxae, 
in most of groove at base of propodeum, irregularly ventrad on 
front margin of lower metapleuron, rather irregularly on submeta- 
