REVISION OF MOTHS OF PRODOXINAE 33 



In T. yuccasella, the pistil is penetrated frequently just below 

 the middle. This is not typical for all species, however, for Trelease 

 (1893) has noted that the females of T. synthetica pierce the upper- 

 most part of the style and thrust the ovipositor down the stylar 

 channel. In the former case, the location of each puncture is not 

 random, but is carefully selected by the female. This is an area 

 usually where the walls of the pistil are thmnest and, for most moths, 

 normally within one of the deeper (prunary) divisions of the young 

 tricarpeUate ovary. Insertion of the egg requu-es approximately 

 one minute. Withdrawal of the ovipositor is often a more laborious 

 task, requu-mg from forty seconds to as long as three minutes, and 

 is accomplished by a series of pulsating, jerky movements. Thi-ough 

 studies of ovarian cross sections, Riley (1892a) has shown that the 

 ovipositor usually enters the locule near the external margin of the 

 ovule and ordinarily does not touch the ovule itseK; rarely is an ovule 

 penetrated during oviposition. 



Oviposition mjury to the young fruit is early noticeable as a dark 

 green, external discoloration in the immediate area of the puncture. 

 As the fruit develops, this becomes a depression, causing the mature 

 pod to exhibit usually a pronounced curvature and median con- 

 striction (figs. 18-20), which have been considered by some botanists 

 to be characteristic for this genus of plants. Several experiments 

 clearly have shown that the yucca moth is responsible for these 

 deformations. Most recently, Webber (1953) reported that although 

 several of the yuccas studied by him commonly or always bore con- 

 stricted fruit, none of the flowers hand-pollinated produced fruit 

 that was in any way deformed. It is evident that fruit constriction 

 results from a failure of the ovules and the surrounding tissue to 

 develop at the oviposition site (fig. 18). It seems very probable 

 that the retardation of ceUular growth in this area is due to an 

 inhibitory substance introduced by the moth during oviposition. 

 Ovule abortion, accompanied by later fruit deformation, occurs 

 independently of larval development. Frequently, constricted fruit 

 pods are to be found that show no other evidence of insect injury. 

 Fm'thermore, successful development of the larva does not seem to 

 accentuate the relative amount of fruit deformation. 



Fruit abnormaUties are most noticeable for those yuccas (the 

 section Chenocarpa in particular) pollinated by T. yuccasella. Some 

 plants occasionally may produce undeformed fruit and still be infested 

 with Tegeticula larvae. The author has examined well-developed 

 fruits of Y. baccata and Y. elata (fig. 14) which externally displayed 

 no signs of oviposition injury, but which, upon dissection, revealed 

 the moth's presence. The fruits of Y. brevifolia typicaUy exhibit 

 little or no deformity. As pointed out by Trelease, this results 



