873 



Fig. 72. — PKt)Doxus marginatus: a, anal ab- 

 doniiual joint of female — X 26; bjo. basal 

 joint of ovipositor; tj o, terminal joint 

 <lo. ; uv. oviduct ; f cliispers of male from 

 ;ibovo - :■' IX; pr, front wing — hair line 

 sliowin}; n:itiira1 size. 



Lave found Prodoxus laivu' in tlic stems of all otluT Yuccas which 

 lun*' been able to cxaininc, and doubt 

 less a number of ()ther species are yet 

 to be discovered and characterized. 

 The species so far known are iiiter- 

 estin^y in that they illustrate in a re 

 markable manner what I haA^e called 

 foituitous variation, or superficial 

 colorational characters; also a great 

 tendency to i>raduate into each other 

 by variations among themselves, not 

 only in the structure of the ovipositor 

 and the male genitalia, but in the wing 

 markings. The time to which these 

 remarks are limited will prevent going 

 into descriptive details, and 1 content 

 myself with illustrating, in this connection, a few of the more distinctly 

 marked species (Figs. 72, 7.'i 74. and 7.")). The genus interests us most, 



however, in indicating how 

 Pronuba, with all her abnor- 

 mal peculiarities, has been 

 evohed: for though we have 

 striking differences in habit 

 and mode of development of 

 larva, pupa, and imago, be- 

 tween Pronuba and Prodoxus, 

 >et the affinities are equally 

 striking, and the two genera 

 exemplify, in an exceptional 

 degree, the power of natural 

 selection to intensify habits 

 and structures in opposing di- 

 rections according to the requirements of the species, Prodoxus is 

 practically dependent upon Pronuba, for if the latter did not fructify 

 the plant the former would in time have no flower-stems to breed in, 

 and while Prodorus has gone on generation after generation, with com- 

 paratively little change, Pronuba has become profoundly specialized to 

 fit it for a more specific purpose. 



Fig. 73.— Prodoxus t-inversus: a, left front wing, 

 hair-line underneath showing natural size; 6, geni- 

 talia of male, dorsal view — X 14; c, do., lateral 

 view — X 18; d, anal joint of female with ovipositor 

 oxserted, lateral view— x 20: c, tip of ovipositor still 

 further enlarged. 



CAPRIFICATION OF THE FIG, 



It was my purpose here to explain to you some interesting facts as to 

 the capriflcation of the fig, and the remarkable structural peculiarities 

 and influence of the caprifig insects. It is, however, a somewhat com- 

 plicated subject, and I could not, within the time allotted to me, do jus- 

 tice both to it and the matter of Yucca pollination. As an indication, 



