504 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 114 



Pupation occurs in the larval tube in the soil. Forbes (1923, p. 119) 

 has characterized the pupa as being heavily sclerotized, suited for 

 coming up through the earth, and having the antenna shorter than 

 the bluntly rounded forewing. The eggs are oval and strongly ridged. 



The Head 



The cephalic structures of the male are deserving of special con^ 

 sideration in view of the fact that they are second only to the male 

 genital organs in furnishing not only good specific characters but also 

 potential generic characters. Although the labial palpi, compound 

 eyes, and antennae are easily observable in pinned specimens, the 

 taxonomic value of the form and vestiture of these structures has 

 been commonly overlooked by previous workers in this family. Only 

 the reduced maxillary palpi apparently fail to offer taxonomic 

 characters below the family level. Identical form and vestiture 

 of the labial palpi, compound eyes, and antennae in either the 

 male or the female are consistently exhibited by all of the individuals 

 in any one species or subspecies. In some cases, these similarities 

 are common to the members of a species group, in which event the 

 cephalic structures assume potential generic value. 



THE LABIAL PALPI 



The writer has spent considerable time studjang the relative 

 lengths of the segments in the denuded labial palpi of the males 

 of the various species of Acrolophidae. The males of the North 

 American species of Acrolophus can be morphologically, although 

 probably not phylogenetically, separated into two distinct groups on 

 the basis of the relative segmental lengths of their labial palpi. 

 Approximately one- third of the species have greatly elongated palpi 

 recurving back over the head and extending across much or all of 

 the dorsum of the thorax; in these the basal segment is never the 

 longest of the three segments. The majority of species exhibit palpi 

 which are short or, in some cases, intermediate in length; in these 

 the basal segment is always the longest of the three segments. 



In those species having the elongate palpi, the heavy and often 

 plumose vestiture almost invariably obscures not only the points of 

 articulation between the segments but also the apical limits of these 

 organs. Thus, the palpus must be denuded in order to ascertain 

 the relative lengths of its segments. The basal segment is always 

 large and recurved back against a considerable portion of the head. 

 This curvature makes accurate measurement of its length quite 

 difficult and any figures obtained for this segment should at best be 

 considered as approximations. The central and apical segments are 

 rarely linear, commonly sublinear, or occasionally somewhat curved, 



