PSILOBETHYLUS IN THE NEW WORLD 
(HYMENOPTERA: BETHYLIDAE) 
By W. L. Brown, Jr. and F. Y. Cheng 
Biological Laboratories, Harvard University 
The family Bethylidae is one of the most unsatisfactorily 
known of the larger hymenopterous assemblages. Present- 
day taxonomy is dependent upon the monograph of Kieffer 
in Das Tierreich (Lief. 41, 1914) and on such meager 
authentically determined material as exists in the larger col- 
lections of insects. Kieffer’s work rests on a very poor 
basic literature, and furthermore, the monograph includes 
many elements like the dryinids, Algoella, Embolemus, etc. 
which cannot now be considered close to the bethylids. The 
subsequent removal of many of these tramontane groups 
does little to relieve the difficulty one meets in trying to use 
Kieffer’s work for practical identification. These considera- 
tions, together with the scarcity of material for study, 
make taxonomic endeavor in the bethylids a frustrating 
experience. 
Interest in a female bethylid received from Dr. F. Bonet 
of Mexico City led to attempts at identification by means 
of Kieffer’s key (op. cit.) , where we ran it down in the 
wingless division to couplet 26, p.233. The choice here 
given was: “Mesonotum und scutellum deutlich” or “Meso- 
notum oder scutellum fehlend.” Our specimen had the 
mesonotum and scutellum apparently weakly separated, 
and we decided in favor of a doubtful identification “cf. 
Psilobethylus.” From Kieffer’s generic characterization 
(p. 274) the specimen differed in having four (vs. three) 
mandibular teeth, but otherwise, agreement was fair. Sent 
to Mr. C. F. W. Muesebeck, the female was identified as 
Psilobethylus and was returned promptly with nine very 
similar females from various parts of the United States. 
Psilobethylus has hitherto been represented by three 
species from the Old World. Only one species, Ps. luteus 
Kieffer (genotype) from Europe, has been known from the 
female sex. The descriptions of luteus leave much to be 
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