166 U. S. NATIONAL MUSEUM BULLETIN 216 



figure 331,b (the point slender, concave above, the ridges of its basal 

 teeth very oblique) ; ovipositor sheath about 0.5 as long as front wing. 



This is a small genus of Holarctic distribution. It includes the 

 three Nearctic species treated below (one of which is Holarctic); an 

 undescribed species in Mexico; the Japanese Iseropus orientalis Uchida 

 1928 and /. epicnapterus Uchida 1928; the Indian Pimpla himalayensis 

 Cameron 1899 and Epiurus satanus Morley 1913; the Oriental Epiurus 

 hakonensis Ashmead 1906; and the European Ichneumon inquisitor 

 Scopoli 1763. The last four species have not previously been referred 

 to Iseropus (new combinations). Epiurus guersifoliae Uchida 1928, 

 E. mencianae Uchida 1935, E. nankingensis Uchida 1931, and E. 

 kimishimae Uchida 1942, we regard as synonyms of hakonensis (new 

 synonymies). E. satanus and Pimpla himalayensis are probably also 

 the same as hakonensis, but we have not been able to verify the 

 synonymy by comparison of specimens with types. There are cer- 

 tainly other Palaearctic species that belong to Iseropus, some of which 

 have already been referred to it, but we have not had the opportunity 

 to study them, and so they are not listed. 



The species of Iseropus are common parasites of flimsy lepidopterous 

 cocoons in exposed situations, as on tree trunks. Lymantriidae, 

 Lasiocampidae, and Notodontidae commonly serve as hosts. The 

 parasite larvae are gregarious, several developing on a single host and 

 spinning their cocoons together, within the host cocoon. 



Keys to the Nearctic species of Iseropus 



MALES 



1. Face white medially, the lateral 0.2 black; temple strongly convex; second 



recurrent vein meeting areolet at or near its middle. 



2. californiensis Cushman 



Face entirely white; temple moderately convex; second recurrent vein meeting 



areolet distinctly beyond its middle 2 



2. Clasper with a short apical point, not projecting conspicuously (fig. 361) ; dark 



bands on hind tibia and tarsus relatively wide, that on second segment of 

 tarsus occupying about 0.4 to 0.6 its length . . 1. stercorator (Fabricius) 

 Clasper with an attenuate apical point, projecting conspicuously (fig. 363); 

 dark bands on hind tibia and tarsus relatively narrow, that on second seg- 

 ment of hind tarsus occupying about 0.2 to 0.3 its length. 



3. coelebs (Walsh) 



FEMALES 



1. Labial palpus pure white; dark bands on hind tibia and tarsus relatively nar- 

 row, that on apex of second segment of hind tarsus occupying 0.25 to 0.35 



its length (fig. 321,1) 3. coelebs (Walsh) 



Labial palpus brown; dark bands on hind tibia and tarsus relatively wide, that 

 on apex of second segment of hind tarsus occupying 0.45 to 0.8 its length 

 321,j,k) • 2 



