1976] 
Porter — Prosthoporus 
273 
cle, at a point about 0.5 the distance between spiracle and apex 
of tergite. Second gastric tergite: thyridium subcircular; surface 
with short, sparse setae. Ovipositor: sheathed portion 0.94 as 
long as hind tibia; slender, moderately compressed; dorsal valve 
on tip smooth, without notch or nodus; ventral valve on tip with 
very strong, inclivously oblique to vertical ridges and produced 
into a lobe that partially encloses the upper valve. 
TYPE Species: Prosthoporus terani new species. 
DISCUSSION: Prosthoporus may be separated from all other 
genera of the Tribe Mesostenini by the following combination 
of characters: occipital carina terminates below a little before 
hypostomal carina; sternaulus faint and only traceable on basal 
half of mesopleuron; whole propodeum behind basal trans-carina 
with regular transverse striae; areolet rectangular, 1.7 as wide 
as high; brachiella absent; first gastric tergite elongate, parallel- 
sided, and with spiracle situated at basal 0.39; ventral valve of 
ovipositor partly overlaps dorsal valve on tip. The position of 
the first tergite spiracle is unusual. Most Mesostenini have this 
spiracle behind the middle of the tergite while only a few have 
it at or slightly before the middle. In Prosthoporus the spiracle 
is located farther basad than in any other mesostenine genus 
known to me. 
Townes (1969, p. 141-145) provides a tentative subtribal clas- 
sification of the mesostenines. Within his framework, Prostho- 
porus shows affinity to the Subtribe Gabuniina in position of 
the first tergite spiracle, structure of the ovipositor tip, and in the 
somewhat inflated female front tibia. However, the foregoing 
are adaptive characters possessed independently by numerous 
Mesostenini that parasitize wood boring beetle larvae and Prostho- 
porus differs substantially from the Gabuniina by having the 
lower mandibular tooth shorter than the upper and by its deeply 
bilobed female fourth front tarsomere. Otherwise, Prosthoporus 
runs easily in Townes’ subtribal key to couplet 17 which differen- 
tiates between the Lymeonina and Ceratocryptina. Here it will 
go unequivocally to neither subtribe as now defined but agrees 
with the Lymeonina in most features except for the rectangular 
areolet which is “much wider than high” as in Ceratocryptina. 
For the present, I consider Prosthoporus a lymeonine but agree 
with Townes (1969, p. 141) that some of the currently recognized 
subtribes of Mesostenini “are doubtless partly artificial and even- 
