—236— 



resulted. The fruit wiihout l,\rvae, bears, with scarcely any exception io 

 those fanniliar with such tokens, the traces of the ovipositor, or of the par- 

 tial feeding? of a perished larva. 



Until the fruit is full grown it is very difficult to detect the larva; 

 and its presence in the softer, partially developed pods is easily over- 

 looked, in ordinary dissection. Such I know to be the fact from exten- 

 ded work in my studies of the hatching and development of the larva. 

 The proportion of infected capsules is best seen in the season when the 

 fruit is matured and the larvae have left it through their characteristic 

 ])erforatiuns. In short, my experience, corroborated by that of others, 

 is, that the proportion is very small indeed in which the larva does not 

 occur, and that such almost always bear evidence of oviposilion havini; 

 taking place. 



Washington, I). C".. January i8th., 1887. 



Remarks upon Prof. Riley's Strictures. 



By Gko. D. Hulst. 



Prof. Riley is right, when he says the Society report referred to by 

 him, misrepresents him. Had he called my attention to it, I should 

 gladly have inserted a correction. So far as it touches Prof. Riley, 1 

 iinend the report, and state as follows: Prof Riley, after many obser\a- 

 tions, concludes that the dehiscent species of Yucca are fertilized only by 

 ihe agency of Pronuba yuccasella. A very large majority of the seed cap- 

 sules of these species shows this by the presence of the larva within; and 

 where the larva is not present. Prof Riley believes the fertilization has 

 been effected by the moth. 



As, at the Society meeting I was speaking of observations upon the 

 dehiscent species only, it it quite likely that the report misrepresents me> 

 as well as Prof. Riley. 



Putting in this amended stiitement, the accuracy of which is wit- 

 nessed by what Prof. Riley says above, I repeat the substance of the re- 

 ))ort, following after; my observations have not brought me to the same 

 conclusion arrived at by Prof. Riley. There is no doubt in my mind 

 that there must be very extensive fertilization of the dehiscent species of 

 Yucca by the agency of bees and other insects. 



The report gives my rea.sons. I will here repeat them more in 

 detail. 



1st. Dr. Engelmann, to whom we are indebted for the liiscovery of 

 the fact that Pronuba is an agent in the fertilization of Yucca (though he 

 »lid not work out the history which Prof Riley has done so well) says 

 in his Monograph of Yucca, (Trans. St. Louis Acad. .Sci. Vol. Ill,) "the 



