36 U.S. NATIONAL MUSEUM BULLETIN 2 55 



such a case in which a yucca (possibly Y. aloifolia), cultivated in 

 Australia, produced fruit. Seed pods from this plant showed no 

 signs of oviposition or larval damage. Yucca whipplei from southern 

 California repeatedly has been observed to bear fruit without the 

 assistance of Tegeticula (Coquillett, 1893; Webber, 1953). This plant 

 was suspected very early by Riley as being capable of selfpollination 

 because of its unique, capitate stigma. Yucca aloifolia from the south- 

 eastern United States also has been suspected of self-pollination 

 (Riley, 1892a). 



Very little evidence has been proposed to demonstrate how great 

 a role apomictic reproduction plays in yucca propagation. Webber 

 (1953) states that except for Y. hrevijolia and Y. whipplei, the south- 

 western yuccas are not reproducing to any extent by seeds. If such 

 is true, then it would appear that most yuccas could survive indefi- 

 nitely through vegetative means without need of the moth's presence. 

 In contrast, if aU yuccas over a large area failed to bloom for a single 

 year, the population of Tegeticula would be precariously reduced, but 

 probably not exterminated because of variances in the length of larval 

 life. Two or three years without flowers being produced, however, 

 most likely would annihilate these moths from a given area, along 

 with any members of the genus Prodoxus. Eventually, of course, 

 the moth population would be restored through emigrations from 

 surrounding areas. 



Although Webber belittles the significance of seed reproduction in 

 Yucca, throughout his paper he emphasizes the important role that 

 hybridization has played in regard to the taxonomic complexity of 

 the genus. Such emphasis, of course, implies yucca production by 

 seeds has been, and perhaps still is, of importance. McKelvey and 

 Sax (1933) likewise have suggested that the perplexing variation and 

 profusion of intermediate forms could be the result of extensive 

 hybridization. Considering the behavior of Tegeticula, it would indeed 

 be remarkable if considerable hybridization had not occurred between 

 various species of Yucca. It need only be remembered that a moth 

 such as r. yuccasella, which is fully capable of feeding upon a great 

 variety of Yucca, is also just as adept at cross-pollinating its various 

 hosts, and has probably made unconscious attempts to do so for 

 thousands of years. Thus, it is very likely that hybridization has 

 evolved as a common phenomenon within this genus of plants. 



Natural enemies. — Only one parasite has been reported from a 

 species of Tegeticula, and that record is questionable (see p. 42). If 

 insect parasitism does occur, then the frequency is evidently quite 

 low. Although the members of Tegeticula are perhaps free from para- 

 sites, predators may exert some population control. The author has 

 observed numerous beetle larvae of the family Cleridae inhabiting 



