16 U.S. NATIONAL MUSEUM BULLETIN 2 55 



Although much remains to be known concerning the biology of 

 Parategeticula, this genus is believed to represent a specialized, stem 

 boring group (C), derived from ancestral Tegeticula, and completely 

 separate from the phyletic line (B') which gave rise to Prodoxus and 

 its relatives. The eggs of Parategeticula are deposited in a very 

 peculiar and unique manner (figs. 33, 34) in the stems of its host. 

 Unfortunately, the habits of the larva are unknown at present. On 

 rarer occasions, the female of Parategeticula inserts her eggs into the 

 coralla of the flower. This habit possibly may be a reflection of an 

 earlier time in which the predecessors of this group fed exclusively 

 within the flowers. Morphologically Parategeticula presents consid- 

 erable evidence of its specialized natui'e. Major among these is the 

 unique ovipositor, which is probably the most modified of any of the 

 plant piercing IVlonotrysia. The reduced palpi and the loss of the 

 epiphysis and frenulum also should be mentioned in this connection. 

 The retention of the maxillary tentacles, along with a behavior for 

 collecting pollen, indicates the ancestry it has in common with 

 Tegeticula. At present it is not known if the females of Parategeticula 

 actually complete the pollination sequence, or whether they merely 

 gather the poUen and then move to other parts of the plant for 

 oviposition, without depositing any pollen on the yucca stigma. 

 Because the life history of Parategeticula demonstrates less restriction 

 to the yucca flower than does Tegeticula, it is possible that the former 

 gradually has acquired a negligible, or less efiicient, role in pollination 

 as compared to that witnessed for Tegeticula. A present failure for 

 the females of Parategeticula to be efficient pollinators probably would 

 be of no great disadvantage, since Tegeticula and Parategeticula are 

 sympatric, as far as is known, in both time and space. Thus, Para- 

 tegeticula, like the members of Prodoxus, may be dependent on the 

 existence of Tegeticula for survival. 



Division B in diagram 1 is characterized by species that are principally 

 stem borers. No member is beheved to have retained a seed boring 

 habit, although some of the less speciahzed members of Prodoxus 

 are known to feed in the fleshy part of the fruit. The genus Prodoxus 

 undoubtedly is the most primitive element of this major division, as 

 is indicated by both morphology and host preference. It is possible 

 that this phyletic line diverged from ancestral Tegeticula (B) after 

 obligatory poUination already had become an estabHshed pattern 

 within the group, and that the loss of this habit accompanied the 

 gradual change in larval behavior. It is also possible, however, that 

 the immediate progenitors of this division never exhibited the special- 

 ized pollinating behavior of Tegeticula, but that they evolved before 

 this habit had developed. 



Division D in diagram 1 represents an important evolutionary step 



