68 UNITED STATES NATIONAL MUSEUM BULLETIN 276 



If there is any doubt as to whether a given specimen is a Mala- 

 cosoma or not, the genitaHa should be checked (especially males). 

 The male genitalia of all species of Malacosoma are similar in their 

 basic structure (fig. 30) and differ greatly from those of any other 

 lasiocampid genera that have been examined. Females are not so 

 easily separated by genitalic characters, but the shape of the genital 

 plate area which surrounds the ostium (figs. 83, 90, 95, 102), whether 

 it is sclerotized or not, is different from females of the other genera 

 which have been examined. In the vast majority of cases, however, 

 both male and female Malacosoma should be readily recognized by the 

 combination of easily visible wing characters given above. 



