THE NEW WORLD GENUS PLUTO (HYMENOPTERA, SPHECIDAE, PSENINI) by J. P. VAN LITH t Allard Piersonstraat 28c, Rotterdam With 71 text-figures Abstract A review of tiie genus Pluto Pate with key to the species is presented. Redescriptions of the forms previously published, first descriptions of some opposite sexes and new distribution data are given. The following new taxa are described: abbreviatus. alphitopus, araguensis, arenivagus cubanus, basifuscus, biformis, castaneipes, colonensis, denticollis, depressus, duckei, emarginatus, evansi, facialis, fritzi, incarina-tus, jugularis. marthae. médius zuliensis, menkei, metanus, nitens, obscurus, occipitalis, punctatellus, pyg-maeus axillaris, rotundus. rufanalis, rugulosus, scytinus. simplicicollis, spangleri, spinicollis, stenopygidialis, stramineipes, strigellus, trilobatus, zonatus. The first review of the genus Pluto Pate {Psenia Malloch) was given by Malloch (1933) in his study on the Psenini of North America. In 1901, Viereck included the two North American species known to him, Mimesa tibialis Cresson and Psen suffusus Fox in his new genus Neofoxia (type species Psen atratus Panzer) together with two species now placed in the genus Psenulus, i.e. Psen frontalis Fox and Psen trisulcus Fox. Malloch (1933) recognized two separate genera, Diodontus Curtis, 1834 {Neofoxia Viereck, now Psenulus Kohl, 1896) and a new genus Psenia, the latter to receive those forms in which "the cubitus of the hind wing is distad of the median transverse vein" (cu-a) as in Diodontus Curtis {Psenulus Kohl) but the "occipital carina is not connected with the carina surrounding the mouth cavity" (hypostomal carina). Malloch in his diagnosis oï Psenia rightly mentions the long, downward directed bristly hair on the mid and hind coxa, but some of the other generic characters enumerated by him apply to North American species only. He described or recorded sixteen taxa, including atricornis from the West Indies, but not argentifrons (Cresson) from Cuba. Pate (1937) changed the generic name into Pluto, Psenia being preoccupied by Psenia Stephens, 1829 (a synonym of Psen Latreille, 1796; type species Sphex atra Fabricius, 1793). In 1946, Pate furnished a good redescription of Pluto argentifrons (Cresson) and pointed out that the females from Cuba, which Malloch associated with the males of atricornis Malloch from Puerto Rico, in fact belong to argentifrons. A few years later Krombein (1949) described arenivagus as a new species from North America. Thus far Mexico and South America had yielded very few species. Cameron (1891) published Psen annulipes (female) from Mexico, Psen médius was described 127
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