A radiographic technique was used to detect hymenopterous parasites of the larch casebearer, <i>Coleophora laricella</i> (Hubner), from Idaho. Pupal characteristics of <i>Bracon pygmaeus</i> Provancher, <i>Spilochalcis albifrons</i> (Walsh), <i>Chrysocharis laricinellae</i> (Ratzeburg), <i>Dicladocerus nearcticus</i> Yoshimoto, <i>Tetrastichus</i> sp., and <i>Mesopolobus verditer</i> (Norton) were examined from radiographs and compared. A key was constructed to identify pupae of these parasites
