OF THE STATE ENTOMOLOGIST. 13^ 



action, swell abnormally. Thus, in making a longitudinal section of 

 the fruit, these swollen ovules often indicate the presence of the worm 

 where it would otherwise be overlooked while very small. 



'' While oviposition generally takes place in the manner described, 

 the moth head outward and straddling two stamens, an entirely op- 

 posite position must sometimes be assumed, since larvas and punc- 

 tures. are not unfrequently found in the upper part of the fruit, espe- 

 cially where a single one is stocked with ten or a dozen larvae, as is 

 sometimes the case.* As the fruit enlarges, the mouth of the punc- 

 ture forms a slight, discolored depression, more noticeable in some 

 varieties than others; but the passage-way becomes obliterated. 



" My observations this summer might be extended much in detail. 

 They have convinced me more than ever that Pronuba is the only 

 insect by the aid of which our Yuccas can be fully fertilized * for I 

 have studied this fertilization diligently night after night, without 

 seeing any other species go near the stigma. The stigmatic opening 

 closes after the first night, and I know of no crepuscular or nocturnal 

 species which could collect the requisite amount of pollen and bring 

 it so to bear on the stigma that each ovule would receive the influ- 

 ence of a pollen grain. The species already eunmeratedf as frequent- 

 ing Yucca are mostly diurnal, and have nothing to do in the work ; 

 and wherever I have excluded the moth from the flowers, by enclos- 

 ing the latter with netting, no fruit has been produced. I am, there- 

 fore, led to believe that the few rare instances of yucca-fertilization, 

 in localities where Pronuba may be presumed not to occur, have been 

 brought about by another insect accidentally, or by the stamens 

 reaching an exceptional length, and the anthers being brought into 

 contact with the stigma by the conniving of the closing petals. I 

 have found the stamens of varying length in the flowers on the same 

 panicle, and in some instances almost as long as the pistil." 



.. * I have counted as many as twenty-one lavvre in a single capsnle ol' what is apparently Y.Jlaccida.. 

 tRep. V, p. 15t^^ 



